Nessie equated plesiosaur equated three meter leopard seal the real lochness monster for Cantore Arithmetic met at the rotation of the lake. The keel to the lake of the shipping news as the story goes to the local library for the fill. A gravel to the affair at the livelihood relieves the mind to the grave and reintroduces the Egyptian for the keel with Khufu’s boat.
Wikipedia: The Khufu ship is an intact full-size solar barque from ancient Egypt. It was sealed into a pit alongside the Great Pyramid of pharaoh Khufu around 2500 BC, during the Fourth Dynasty of the ancient Egyptian Old Kingdom. Like other buried Ancient Egyptian ships, it was part of the extensive grave goods intended for use in the afterlife. The Khufu ship is one of the oldest, largest and best-preserved vessels from antiquity. It is 43.4 metres (142 ft) long and 5.9 metres (19 ft) wide, and is the world's oldest intact ship. It has been described as "a masterpiece of woodcraft" that could sail today if put into a lake or a river.
The ship was preserved in the Giza Solar boat museum, but was moved to the Grand Egyptian Museum in August 2021.
The three meter leopard seal corrects the plus to addition and by subtraction introduced the road, this apple to the grove is a tree. Mechanical to the rib brings to fruition the mechanic as a Masonic should the lodge reboot.
American language
American language(s) may refer to:
- Indigenous languages of the Americas, languages spoken by indigenous peoples from North America and South America
- Languages of North America, indigenous, (former) colonial, and immigrant languages spoken in North America
- Languages of the United States, numerous languages spoken in the US
- Languages of South America, indigenous, (former) colonial, and immigrant languages spoken in South America
- The American Language, a 1919 book
See also[edit]
- American Sign Language, the sign language of deaf communities in the US and English-speaking parts of Canada
- American English
If an internal link led you here, you may wish to change the link to point directly to the intended article.
Metre
| metre | |
|---|---|
 Seal of the International Bureau of Weights and Measures (BIPM) – Use measure (Greek: ΜΕΤΡΩ ΧΡΩ) | |
| General information | |
| Unit system | SI |
| Unit of | length |
| Symbol | m[1] |
| Conversions | |
| 1 m[1] in ... | ... is equal to ... |
| SI units | |
| Imperial/US units | |
| Nautical units | ≈ 0.00053996 nmi |
The metre (or meter in American spelling; symbol: m) is the base unit of length in the International System of Units (SI).
The metre was originally defined in 1791 as one ten-millionth of the distance from the equator to the North Pole along a great circle, so the Earth's circumference is approximately 40000 km. In 1799, the metre was redefined in terms of a prototype metre bar. The actual bar used was changed in 1889. In 1960, the metre was redefined in terms of a certain number of wavelengths of a certain emission line of krypton-86.
The current definition was adopted in 1983 and modified slightly in 2002 to clarify that the metre is a measure of proper length. From 1983 until 2019, the metre was formally defined as the length of the path travelled by light in a vacuum in 1299792458 of a second. After the 2019 redefinition of the SI base units, this definition was rephrased to include the definition of a second in terms of the caesium frequency ΔνCs.
Spelling[edit]
Metre is the standard spelling of the metric unit for length in nearly all English-speaking nations; the exceptions are the United States[2][3][4][5] and the Philippines,[6] which use meter. Other West Germanic languages, such as German and Dutch, and North Germanic languages, such as Danish, Norwegian, and Swedish,[7] likewise spell the word Meter or meter.
Measuring devices (such as ammeter, speedometer) are spelled "-meter" in all variants of English.[8] The suffix "-meter" has the same Greek origin as the unit of length.[9][10]
Etymology[edit]
The etymological roots of metre can be traced to the Greek verb μετρέω (metreo) (to measure, count or compare) and noun μέτρον (metron) (a measure), which were used for physical measurement, for poetic metre and by extension for moderation or avoiding extremism (as in "be measured in your response"). This range of uses is also found in Latin (metior, mensura), French (mètre, mesure), English and other languages. The Greek word is derived from the Proto-Indo-European root *meh₁- 'to measure'. The motto ΜΕΤΡΩ ΧΡΩ(metro chro) in the seal of the International Bureau of Weights and Measures (BIPM), which was a saying of the Greek statesman and philosopher Pittacus of Mytilene and may be translated as "Use measure!", thus calls for both measurement and moderation. The use of the word metre (for the French unit mètre) in English began at least as early as 1797.[11]
History of definition [edit]
 | This section duplicates the scope of other articles, specifically History of the metre.(August 2023) |
Pendulum or meridian[edit]
In 1671, Jean Picard measured the length of a "seconds pendulum" and proposed a unit of measurement twice that length to be called the universal toise (French: Toise universelle).[12][13] In 1675, Tito Livio Burattini suggested the term metre for a unit of length based on a pendulum length, but then it was discovered that the length of a seconds pendulum varies from place to place.[14][15][16][17][18][19][20][21][22]
Since Eratosthenes, geographers had used meridian arcs to assess the size of the Earth, which in 1669, Jean Picard determined to have a radius of 3269000 toises, treated as a simple sphere. In the 18th century, geodesygrew in importance as a means of empirically demonstrating the theory of gravity, which Émilie du Châteletpromoted in France in combination with Leibniz's mathematical work,[23] and because the radius of the Earth was the unit to which all celestial distances were to be referred.[24][25][26]
Meridional definition[edit]
As a result of the Lumières and during the French Revolution, the French Academy of Sciences charged a commission with determining a single scale for all measures. On 7 October 1790 that commission advised the adoption of a decimal system, and on 19 March 1791 advised the adoption of the term mètre ("measure"), a basic unit of length, which they defined as equal to one ten-millionth of the quarter meridian, the distance between the North Pole and the Equator along the meridian through Paris.[27][28][29][30][31] On 26 March 1791, the French National Constituent Assembly adopted the proposal.[11][32]
The French Academy of Sciences commissioned an expedition led by Jean Baptiste Joseph Delambre and Pierre Méchain, lasting from 1792 to 1799, which attempted to accurately measure the distance between a belfry in Dunkirk and Montjuïc castle in Barcelona at the longitude of the Paris Panthéon (see meridian arc of Delambre and Méchain).[33] The expedition was fictionalised in Denis Guedj, Le Mètre du Monde.[34] Ken Alder wrote factually about the expedition in The Measure of All Things: the seven year odyssey and hidden error that transformed the world.[35]
This portion of the Paris meridian was to serve as the basis for the length of the half meridian connecting the North Pole with the Equator. From 1801 to 1812 France adopted this definition of the metre as its official unit of length based on results from this expedition combined with those of the Geodesic Mission to Peru.[36][37] The latter was related by Larrie D. Ferreiro in Measure of the Earth: The Enlightenment Expedition That Reshaped Our World.[38][39]
In the 19th century, geodesy underwent a revolution through advances in mathematics as well as improvements in the instruments and methods of observation, for instance accounting for individual bias in terms of the personal equation. The application of the least squares method to meridian arc measurements demonstrated the importance of the scientific method in geodesy. On the other hand, the invention of the telegraph made it possible to measure parallel arcs, and the improvement of the reversible pendulum gave rise to the study of the Earth's gravitational field. A more accurate determination of the Figure of the Earth would soon result from the measurement of the Struve Geodetic Arc (1816–1855) and would have given another value for the definition of this standard of length. This did not invalidate the metre but highlighted that progress in science would allow better measurement of Earth's size and shape.[40][41][42][43]
In 1832, Carl Friedrich Gauss studied the Earth's magnetic field and proposed adding the second to the basic units of the metre and the kilogram in the form of the CGS system (centimetre, gram, second). In 1836, he founded the Magnetischer Verein, the first international scientific association, in collaboration with Alexander von Humboldt and Wilhelm Edouard Weber. The coordination of the observation of geophysical phenomena such as the Earth's magnetic field, lightning and gravity in different points of the globe stimulated the creation of the first international scientific associations. The foundation of the Magnetischer Verein was followed by that of the Central European Arc Measurement (German: Mitteleuropaïsche Gradmessung) on the initiative of Johann Jacob Baeyer in 1863, and by that of the International Meteorological Organisation whose second president, the Swiss meteorologist and physicist, Heinrich von Wild represented Russia at the International Committee for Weights and Measures (CIPM).[44][45][46][47][48][49]
International prototype metre bar[edit]
In 1816, Ferdinand Rudolph Hassler was appointed first Superintendent of the Survey of the Coast. Trained in geodesy in Switzerland, France and Germany, Hassler had brought a standard metre made in Paris to the United States in 1805. He designed a baseline apparatus which instead of bringing different bars in actual contact during measurements, used only one bar calibrated on the metre and optical contact. Thus the metre became the unit of length for geodesy in the United States.[51][52][53][54]
Since 1830, Hassler was also head of the Bureau of Weights and Measures which became a part of the Coast Survey. He compared various units of length used in the United States at that time and measured coefficients of expansion to assess temperature effects on the measurements.[55]
In 1841, Friedrich Wilhelm Bessel, taking into account errors which had been recognized by Louis Puissant in the French meridian arc comprising the arc measurement of Delambre and Méchain which had been extended southward by François Arago and Jean-Baptiste Biot, recalculated the flattening of the Earth ellipsoid making use of nine more arc measurements, namely Peruan, Prussian, first East-Indian, second East-Indian, English, Hannover, Danish, Russian and Swedish covering almost 50 degrees of latitude. He proposed a reference ellipsoid much closer to reality than that which had been used to compute the metre and stated that the Earth quadrant used for determining the length of the metre was nothing more than a rather imprecise conversion factor between the toise and the metre.[56][57][58]
Regarding the precision of the conversion from the toise to the metre, both units of measurement were then defined by primary standards, and unique artifacts made of different alloys with distinct coefficients of expansion were the legal basis of units of length. A wrought iron ruler, the Toise of Peru, also called Toise de l'Académie, was the French primary standard of the toise, and the metre was officially defined by the Mètre des Archives made of platinum. Besides the latter, another platinum and twelve iron standards of the metre were made in 1799.[59][54][49][60][61]
One of them became known as the Committee Meter in the United States and served as standard of length in the Coast Survey until 1890. According to geodesists, these standards were secondary standards deduced from the Toise of Peru. In Europe, surveyors continued to use measuring instruments calibrated on the Toise of Peru. Among these, the toise of Bessel and the apparatus of Borda were respectively the main references for geodesy in Prussiaand in France. A French scientific instrument maker, Jean Nicolas Fortin, had made three direct copies of the Toise of Peru, one for Friedrich Georg Wilhelm von Struve, a second for Heinrich Christian Schumacher in 1821 and a third for Friedrich Bessel in 1823.[62][54][49][60][63]
On the subject of the theoretical definition of the metre, it had been inaccessible and misleading at the time of Delambre and Mechain arc measurement, as the geoid is a ball, which on the whole can be assimilated to an oblate spheroid, but which in detail differs from it so as to prohibit any generalization and any extrapolation. As early as 1861, after Friedrich von Schubert showed that the different meridians were not of equal length, Elie Ritter, a mathematician from Geneva, deduced from a computation based on eleven meridian arcs covering 86 degrees that the meridian equation differed from that of the ellipse: the meridian was swelled about the 45th degree of latitude by a layer whose thickness was difficult to estimate because of the uncertainty of the latitude of some stations, in particular that of Montjuïc in the French meridian arc. By measuring the latitude of two stations in Barcelona, Méchain had found that the difference between these latitudes was greater than predicted by direct measurement of distance by triangulation. Indeed, clearance in the central axis of the repeating circle caused wear and consequently the zenith measurements contained significant systematic errors.[64]Moreover, we know now that, in addition to these errors in the survey of Delambre and Méchain, an unfavourable vertical deflection gave an inaccurate determination of Barcelona's latitude and a metre "too short" compared to a more general definition taken from the average of a large number of arcs.[65][66][58][67][68]
Nevertheless Ferdinand Rudolph Hassler's use of the metre in coastal survey contributed to the introduction of the Metric Act of 1866 allowing the use of the metre in the United States, and also played an important role in the choice of the metre as international scientific unit of length and the proposal by the European Arc Measurement (German: Europäische Gradmessung) to "establish a European international bureau for weights and measures". However, in 1866, the most important concern was that the Toise of Peru, the standard of the toise constructed in 1735 for the French Geodesic Mission to the Equator, might be so much damaged that comparison with it would be worthless, while Bessel had questioned the accuracy of copies of this standard belonging to Altona and Koenigsberg Observatories, which he had compared to each other about 1840. Indeed when the primary Imperial yard standard was partially destroyed in 1834, a new standard of reference had been constructed using copies of the "Standard Yard, 1760" instead of the pendulum's length as provided for in the Weights and Measures Act of 1824.[69][70][71][60][72][73][74]
In 1864, Urbain Le Verrier refused to join the first general conference of the Central European Arc Measurement because the French geodetic works had to be verified.[75] In 1866, at the meeting of the Permanent Commission of the association in Neuchâtel, Antoine Yvon Villarceau announced that he had checked eight points of the French arc. He confirmed that the metre was too short.[76][58][77][78][65]
In 1867 at the second general conference of the International Association of Geodesy held in Berlin, the question of an international standard unit of length was discussed in order to combine the measurements made in different countries to determine the size and shape of the Earth.[79][80][81] According to a preliminary proposal made in Neuchâtel the precedent year, the general conference recommended the adoption of the metre in replacement of the toise, the creation of an International Metre Commission, and the foundation of a World Institute for the Comparison of Geodetic Standards, the first step towards the creation of the International Bureau of Weights and Measures.[82][79][81][83][84]
Hassler's metrological and geodetic work also had a favourable response in Russia.[55] In 1869, the Saint Petersburg Academy of Sciences sent to the French Academy of Sciences a report drafted by Otto Wilhelm von Struve, Heinrich von Wild and Moritz von Jacobi inviting his French counterpart to undertake joint action to ensure the universal use of the metric system in all scientific work.[74]
In the 1870s and in light of modern precision, a series of international conferences was held to devise new metric standards. When a conflict broke out regarding the presence of impurities in the metre-alloy of 1874, a member of the Preparatory Committee since 1870 and Spanish representative at the Paris Conference in 1875, Carlos Ibáñez e Ibáñez de Ibero intervened with the French Academy of Sciences to rally France to the project to create an International Bureau of Weights and Measures equipped with the scientific means necessary to redefine the units of the metric system according to the progress of sciences.[85][86][49][87]
The Metre Convention (Convention du Mètre) of 1875 mandated the establishment of a permanent International Bureau of Weights and Measures (BIPM: Bureau International des Poids et Mesures) to be located in Sèvres, France. This new organisation was to construct and preserve a prototype metre bar, distribute national metric prototypes, and maintain comparisons between them and non-metric measurement standards. The organisation distributed such bars in 1889 at the first General Conference on Weights and Measures (CGPM: Conférence Générale des Poids et Mesures), establishing the International Prototype Metre as the distance between two lines on a standard bar composed of an alloy of 90% platinum and 10% iridium, measured at the melting point of ice.[85]
At that time, statisticians knew that scientific observations are marred by two distinct types of errors, constant errors on the one hand, and fortuitous errors, on the other hand. The effects of the latter can be mitigated by the least-squares method. Constant or regular errors on the contrary must be carefully avoided, because they arise from one or more causes that constantly act in the same way and have the effect of always altering the result of the experiment in the same direction. They therefore deprive of any value the observations that they impinge. However, the distinction between systematic and random errors is far from being as sharp as one might think at first assessment. In reality, there are no or very few random errors. As science progresses, the causes of certain errors are sought out, studied, their laws discovered. These errors pass from the class of random errors into that of systematic errors. The ability of the observer consists in discovering the greatest possible number of systematic errors in order to be able, once he has become acquainted with their laws, to free his results from them using a method or appropriate corrections.[88][89] For metrology the matter of expansibility was fundamental; as a matter of fact the temperature measuring error related to the length measurement in proportion to the expansibility of the standard and the constantly renewed efforts of metrologists to protect their measuring instruments against the interfering influence of temperature revealed clearly the importance they attached to the expansion-induced errors. It was thus crucial to compare at controlled temperatures with great precision and to the same unit all the standards for measuring geodetic baselines and all the pendulum rods. As Carlos Ibáñez e Ibáñez de Ibero stated, the progress of metrology combined with those of gravimetry through improvement of Kater's pendulum led to a new era of geodesy. If precision metrology had needed the help of geodesy, the latter could not continue to prosper without the help of metrology. It was then necessary to define a single unit to express all the measurements of terrestrial arcs and all determinations of the force of gravity by the mean of pendulum. Metrology had to create a common unit, adopted and respected by all civilized nations.[90][41] The comparison of the new prototypes of the metre with each other and with the Mètre des Archives involved the development of special measuring equipment and the definition of a reproducible temperature scale. The BIPM's thermometry work led to the discovery of special alloys of iron-nickel, in particular invar, for which its director, the Swiss physicist Charles-Edouard Guillaume, was granted the Nobel Prize for physics in 1920.[91][92]
As the figure of the Earth could be inferred from variations of the seconds pendulum length, the United States Coast Survey instructed Charles Sanders Peirce in the spring of 1875 to proceed to Europe for the purpose of making pendulum experiments to chief initial stations for operations of this sort, in order to bring the determinations of the forces of gravity in America into communication with those of other parts of the world; and also for the purpose of making a careful study of the methods of pursuing these researches in the different countries of Europe. In 1886 the association of geodesy changed name for the International Geodetic Association, which Carlos Ibáñez e Ibáñez de Ibero presided up to his death in 1891. During this period the International Geodetic Association (German: Internationale Erdmessung) gained worldwide importance with the joining of United States, Mexico, Chile, Argentina, and Japan.[93][94][95][96][97]
In 1901, Friedrich Robert Helmert found essentially by gravimetry, a value of Earth ellipsoid of 1/298.3, while the analysis of the first results from satellite measurements would fix this value as 1/298.25.[98] Nowadays the practical realisation of the metre is possible everywhere thanks to the atomic clocks embedded in GPS satellites.[99]
Wavelength definition[edit]
In 1873, James Clerk Maxwell suggested that light emitted by an element be used as the standard both for the metre and for the second. These two quantities could then be used to define the unit of mass.[100]
In 1893, the standard metre was first measured with an interferometer by Albert A. Michelson, the inventor of the device and an advocate of using some particular wavelength of light as a standard of length. By 1925, interferometry was in regular use at the BIPM. However, the International Prototype Metre remained the standard until 1960, when the eleventh CGPM defined the metre in the new International System of Units (SI) as equal to 1650763.73wavelengths of the orange-red emission line in the electromagnetic spectrum of the krypton-86 atom in a vacuum.[101]
Speed of light definition[edit]
To further reduce uncertainty, the 17th CGPM in 1983 replaced the definition of the metre with its current definition, thus fixing the length of the metre in terms of the second and the speed of light:[102][103]
- The metre is the length of the path travelled by light in vacuum during a time interval of 1299792458 of a second.
This definition fixed the speed of light in vacuum at exactly 299792458 metres per second[102] (≈300000 km/s or ≈1.079 billion km/hour[104]). An intended by-product of the 17th CGPM's definition was that it enabled scientists to compare lasers accurately using frequency, resulting in wavelengths with one-fifth the uncertainty involved in the direct comparison of wavelengths, because interferometer errors were eliminated. To further facilitate reproducibility from lab to lab, the 17th CGPM also made the iodine-stabilised helium–neon laser "a recommended radiation" for realising the metre.[105] For the purpose of delineating the metre, the BIPM currently considers the HeNe laser wavelength, λHeNe, to be 632.99121258 nm with an estimated relative standard uncertainty (U) of 2.1×10−11.[105][106][107]
This uncertainty is currently one limiting factor in laboratory realisations of the metre, and it is several orders of magnitude poorer than that of the second, based upon the caesium fountain atomic clock (U = 5×10−16).[108] Consequently, a realisation of the metre is usually delineated (not defined) today in labs as 1579800.762042(33) wavelengths of helium-neon laser light in a vacuum, the error stated being only that of frequency determination.[105] This bracket notation expressing the error is explained in the article on measurement uncertainty.
Practical realisation of the metre is subject to uncertainties in characterising the medium, to various uncertainties of interferometry, and to uncertainties in measuring the frequency of the source.[109] A commonly used medium is air, and the National Institute of Standards and Technology (NIST) has set up an online calculator to convert wavelengths in vacuum to wavelengths in air.[110] As described by NIST, in air, the uncertainties in characterising the medium are dominated by errors in measuring temperature and pressure. Errors in the theoretical formulas used are secondary.[111]
By implementing a refractive index correction such as this, an approximate realisation of the metre can be implemented in air, for example, using the formulation of the metre as 1579800.762042(33) wavelengths of helium–neon laser light in a vacuum, and converting the wavelengths in a vacuum to wavelengths in air. Air is only one possible medium to use in a realisation of the metre, and any partial vacuum can be used, or some inert atmosphere like helium gas, provided the appropriate corrections for refractive index are implemented.[112]
The metre is defined as the path length travelled by light in a given time, and practical laboratory length measurements in metres are determined by counting the number of wavelengths of laser light of one of the standard types that fit into the length,[115] and converting the selected unit of wavelength to metres. Three major factors limit the accuracy attainable with laser interferometers for a length measurement:[109][116]
- uncertainty in vacuum wavelength of the source,
- uncertainty in the refractive index of the medium,
- least count resolution of the interferometer.
Of these, the last is peculiar to the interferometer itself. The conversion of a length in wavelengths to a length in metres is based upon the relation
which converts the unit of wavelength λ to metres using c, the speed of light in vacuum in m/s. Here n is the refractive index of the medium in which the measurement is made, and f is the measured frequency of the source. Although conversion from wavelengths to metres introduces an additional error in the overall length due to measurement error in determining the refractive index and the frequency, the measurement of frequency is one of the most accurate measurements available.[116]
The CIPM issued a clarification in 2002:
Timeline[edit]
| Date | Deciding body | Decision |
|---|---|---|
| 8 May 1790 | French National Assembly | The length of the new metre to be equal to the length of a pendulum with a half-period of one second.[36] |
| 30 Mar 1791 | French National Assembly | Accepts the proposal by the French Academy of Sciences that the new definition for the metre be equal to one ten-millionth of the length of a great circle quadrant along the Earth's meridian through Paris, that is the distance from the equator to the north pole along that quadrant.[117] |
| 1795 | Provisional metre bar made of brass and based on Paris meridan arc (French: Méridienne de France) measured by Nicolas-Louis de Lacaillle and Cesar-François Cassini de Thury, legally equal to 443.44 lines of the toise du Pérou (a standard French unit of length from 1766).[36][37][118][119] [The line was 1/864 of a toise.] | |
| 10 Dec 1799 | French National Assembly | Specifies the platinum metre bar, presented on 22 June 1799 and deposited in the National Archives, as the final standard. Legally equal to 443.296 lines on the toise du Pérou.[119] |
| 24–28 Sept 1889 | 1st General Conference on Weights and Measures(CGPM) | Defines the metre as the distance between two lines on a standard bar of an alloy of platinum with 10% iridium, measured at the melting point of ice.[119][120] |
| 27 Sept – 6 Oct 1927 | 7th CGPM | Redefines the metre as the distance, at 0 °C (273 K), between the axes of the two central lines marked on the prototype bar of platinum-iridium, this bar being subject to one standard atmosphere of pressure and supported on two cylinders of at least 10 mm (1 cm) diameter, symmetrically placed in the same horizontal plane at a distance of 571 mm (57.1 cm) from each other.[121] |
| 14 Oct 1960 | 11th CGPM | Defines the metre as 1650763.73 wavelengths in a vacuum of the radiation corresponding to the transition between the 2p10 and 5d5 quantum levels of the krypton-86 atom.[122] |
| 21 Oct 1983 | 17th CGPM | Defines the metre as the length of the path travelled by light in a vacuum during a time interval of 1299 792 458 of a second.[123][124] |
| 2002 | International Committee for Weights and Measures(CIPM) | Considers the metre to be a unit of proper length and thus recommends this definition be restricted to "lengths ℓ which are sufficiently short for the effects predicted by general relativity to be negligible with respect to the uncertainties of realisation".[125] |
| Basis of definition | Date | Absolute uncertainty | Relative uncertainty |
|---|---|---|---|
| 110 000 000 part of the quadrant along the meridian, measurement by Delambre and Méchain (443.296 lines) | 1795 | 500–100 μm | 10−4 |
| First prototype Mètre des Archives platinum bar standard | 1799 | 50–10 μm | 10−5 |
| Platinum-iridium bar at melting point of ice (1st CGPM) | 1889 | 0.2–0.1 μm (200–100 nm) | 10−7 |
| Platinum-iridium bar at melting point of ice, atmospheric pressure, supported by two rollers (7th CGPM) | 1927 | n.a. | n.a. |
| Hyperfine atomic transition; 1650763.73 wavelengths of light from a specified transition in krypton-86(11th CGPM) | 1960 | 4 nm | 4×10−9[127] |
| Length of the path travelled by light in a vacuum in 1299 792 458 second (17th CGPM) | 1983 | 0.1 nm | 10−10 |
Early adoptions of the metre internationally[edit]
In France, the metre was adopted as an exclusive measure in 1801 under the Consulate. This continued under the First French Empire until 1812, when Napoleon decreed the introduction of the non-decimal mesures usuelles, which remained in use in France up to 1840 in the reign of Louis Philippe.[36]Meanwhile, the metre was adopted by the Republic of Geneva.[128] After the joining of the canton of Geneva to Switzerland in 1815, Guillaume Henri Dufour published the first official Swiss map, for which the metre was adopted as the unit of length.[129][130]
Louis Napoléon Bonaparte, a Swiss–French binational officer, was present when a baseline was measured near Zürich for the Dufour map, which would win the gold medal for a national map at the Exposition Universelle of 1855.[131][132][133] Among the scientific instruments calibrated on the metre that were displayed at the Exposition Universelle, was Brunner's apparatus, a geodetic instrument devised for measuring the central baseline of Spain, whose designer, Carlos Ibáñez e Ibáñez de Ibero would represent Spain at the International Statistical Institute. In 1885, in addition to the Exposition Universelle and the second Statistical Congress held in Paris, an International Association for Obtaining a Uniform Decimal System of Measures, Weights, and Coins was created there.[49][134][135][136]
Copies of the Spanish standard were made for Egypt, France and Germany.[137][138][139] These standards were compared to each other and with the Borda apparatus, which was the main reference for measuring all geodetic bases in France.[137][140][93] In 1869, Napoleon III convened the International Metre Commission, which met in Paris in 1870. The Franco-Prussian War broke out, the Second French Empire collapsed, but the metre survived.[141][71]
Metre adoption dates by country[edit]
- France: 1801 - 1812, then 1840,[36]
- Republic of Geneva, Switzerland: 1813,[142]
- Kingdom of the Netherlands: 1820,
- Kingdom of Belgium: 1830,
- Chile: 1848,
- Kingdom of Sardinia, Italy: 1850,
- Spain: 1852,
- Portugal: 1852,
- Colombia: 1853,
- Ecuador: 1856,
- Mexico: 1857,
- Brazil: 1862,
- Argentina: 1863,
- Italy: 1863,
- German Empire, Germany: 1872,
- Austria, 1875,
- Switzerland: 1877.[142]
SI prefixed forms of metre[edit]
SI prefixes can be used to denote decimal multiples and submultiples of the metre, as shown in the table below. Long distances are usually expressed in km, astronomical units (149.6 Gm), light-years (10 Pm), or parsecs (31 Pm), rather than in Mm, Gm, Tm, Pm, Em, Zm or Ym; "30 cm", "30 m", and "300 m" are more common than "3 dm", "3 dam", and "3 hm", respectively.
The terms micron and millimicron have been used instead of micrometre (μm) and nanometre (nm), respectively, but this practice is discouraged.[143]
| Submultiples | Multiples | |||||
|---|---|---|---|---|---|---|
| Value | SI symbol | Name | Value | SI symbol | Name | |
| 10−1 m | dm | decimetre | 101 m | dam | decametre | |
| 10−2 m | cm | centimetre | 102 m | hm | hectometre | |
| 10−3 m | mm | millimetre | 103 m | km | kilometre | |
| 10−6 m | µm | micrometre | 106 m | Mm | megametre | |
| 10−9 m | nm | nanometre | 109 m | Gm | gigametre | |
| 10−12 m | pm | picometre | 1012 m | Tm | terametre | |
| 10−15 m | fm | femtometre | 1015 m | Pm | petametre | |
| 10−18 m | am | attometre | 1018 m | Em | exametre | |
| 10−21 m | zm | zeptometre | 1021 m | Zm | zettametre | |
| 10−24 m | ym | yoctometre | 1024 m | Ym | yottametre | |
| 10−27 m | rm | rontometre | 1027 m | Rm | ronnametre | |
| 10−30 m | qm | quectometre | 1030 m | Qm | quettametre | |
Equivalents in other units[edit]
| Metric unit expressed in non-SI units | Non-SI unit expressed in metric units | |||||||
|---|---|---|---|---|---|---|---|---|
| 1 metre | ≈ | 1.0936 | yard | 1 yard | = | 0.9144 | metre | |
| 1 metre | ≈ | 39.370 | inches | 1 inch | = | 0.0254 | metre | |
| 1 centimetre | ≈ | 0.39370 | inch | 1 inch | = | 2.54 | centimetres | |
| 1 millimetre | ≈ | 0.039370 | inch | 1 inch | = | 25.4 | millimetres | |
| 1 metre | = | 1010 | ångström | 1 ångström | = | 10−10 | metre | |
| 1 nanometre | = | 10 | ångström | 1 ångström | = | 100 | picometres | |
Within this table, "inch" and "yard" mean "international inch" and "international yard"[144] respectively, though approximate conversions in the left column hold for both international and survey units.
- "≈" means "is approximately equal to";
- "=" means "is exactly equal to".
One metre is exactly equivalent to 5 000127 inches and to 1 2501 143 yards.
A simple mnemonic aid exists to assist with conversion, as three "3"s:
- 1 metre is nearly equivalent to 3 feet 33⁄8 inches. This gives an overestimate of 0.125 mm; however, the practice of memorising such conversion formulas has been discouraged in favour of practice and visualisation of metric units.
The ancient Egyptian cubit was about 0.5 m (surviving rods are 523–529 mm).[145] Scottish and English definitions of the ell (two cubits) were 941 mm (0.941 m) and 1143 mm (1.143 m) respectively.[146][147] The ancient Parisian toise (fathom) was slightly shorter than 2 m and was standardised at exactly 2 m in the mesures usuelles system, such that 1 m was exactly 1⁄2 toise.[148] The Russian verst was 1.0668 km.[149] The Swedish mil was 10.688 km, but was changed to 10 km when Sweden converted to metric units.[150]
Longship
Longships were a type of specialised Scandinavian warships that have a long history in Scandinavia, with their existence being archaeologically proven[1] and documented from at least the fourth century BC. Originally invented and used by the Norsemen (commonly known as the Vikings) for commerce, exploration, and warfare during the Viking Age, many of the longship's characteristics were adopted by other cultures, like Anglo-Saxons, and continued to influence shipbuilding for centuries.
The longship's design evolved over many centuries, and continued up until the sixth century with clinker-built ships like Nydam. The character and appearance of these ships have been reflected in Scandinavian boatbuilding traditions to the present day. The particular skills and methods employed in making longships are still used worldwide, often with modern adaptations. They were all made out of wood, with cloth sails (woven wool), and had several details and carvings on the hull.
Characteristics[edit]
The longships were characterized as graceful, long, narrow, and light, with a shallow-draft hull designed for speed. The ship's shallow draft allowed navigation in waters only one meter deep and permitted arbitrary beach landings, while its light weight enabled it to be carried over portages or used bottom-up for shelter in camps. Longships were fitted with oars along almost the entire length of the boat itself. Later versions had a rectangular sail on a single mast, which was used to replace or augment the effort of the rowers, particularly during long journeys.[2] The average speed of Viking ships varied from ship to ship, but lay in the range of 5–10 knots (9.3–18.5 km/h) and the maximum speed of a longship under favorable conditions was around 15 knots (28 km/h).[3] The Viking Ship museum in Oslo houses the remains of three such ships, the Oseberg, the Gokstad and the Tune ship.[4]
History[edit]
The Viking longships were powerful naval weapons in their time and were highly valued possessions. Archaeological finds show that the Viking ships were not standardized. Ships varied from designer to designer and place to place and often had regional characteristics. For example, the choice of material was mostly dictated by the regional forests, such as pine from Norway and Sweden, and oak from Denmark. Moreover, each Viking longship had particular features adjusted to the natural conditions under which it was sailed.[5]
They were owned by coastal farmers, and by the leidang system, in times of conflict the King could quickly assemble a large and powerful war fleet. While longships were used by the Norse in warfare, they were mostly used as troop transports, not warships. In the tenth century, longships would sometimes be tied together in offshore battles to form a steady platform for infantry warfare. During the ninth-century peak of the Viking expansion, large fleets set out to attack the degrading Frankish empire by attacking navigable rivers such as the Rhine, the Seine, the Loire and others. Rouen was sacked in 841, the year after the death of Louis the Pious, a son of Charlemagne. Quentovic, near modern Étaples, was attacked in 842 and 600 Danish ships attacked Hamburg in 845. In the same year, 129 ships returned to attack the Seine.[6] They were called "dragon ships" by enemies such as the English[7] because some had a dragon-shaped decoration atop the bow beam. The Norse had a strong sense of naval architecture, and during the early medieval period, they were advanced for their time.[8][9]
Types of longships[edit]
Longships can be classified into a number of different types, depending on size, construction details, and prestige. The most common way to classify longships is by the number of rowing positions on board.
Karvi[edit]
The Karvi (or Karve) is the smallest vessel that is considered a longship. According to the tenth-century Gulating Law, a ship with 13 rowing benches is the smallest ship suitable for military use. A ship with 6 to 16 benches would be classified as a Karvi. These ships were considered to be "general purpose" ships, mainly used for fishing and trade, but occasionally commissioned for military use. While most longships held a length to width ratio of 7:1, the Karvi ships were closer to 9:2.[citation needed] The Gokstad Ship is a famous Karvi ship, built around the end of the ninth century, excavated in 1880 by Nicolay Nicolaysen. It was approximately 23 m (75 feet) long with 16 rowing positions.
Snekkja[edit]
The snekkja (or snekke) was typically the smallest longship used in warfare and was classified as a ship with at least 20 rowing benches. A typical snekkja might have a length of 17 m (56 feet), a width of 2.5 m (8.2 feet), and a draught of only 0.5 m (1.6 feet). It would carry a crew of around 41 men (40 oarsmen and one cox).
The snekkja was one of the most common types of ships. According to Viking lore, Canute the Great used 1,200 in Norway in 1028.[10]
The Norwegian type snekkja typically had more draught than the Danish ships designed for low coasts and beaches. A snekkja was so light that it had no need of ports – it could simply be beached, and even carried across a portage.
The snekkja continued to evolve after the end of the Viking age, with later Norwegian examples becoming larger and heavier than Viking age ships. A modern version is still being used in Scandinavia, and is now called snipa in Swedish and snekke in Norwegian.
Skeid[edit]
Skeid (skeið), meaning 'slider' (referring to a sley, a weavers reed, or to a sheath that a knife slides into) and probably connoting 'speeder' (referring to a running race) (Zoega, Old Icelandic Dictionary). These ships were larger warships, consisting of more than 30 rowing benches. Ships of this classification are some of the largest (see Busse) longships ever discovered. A group of these ships were discovered by Danish archaeologists in Roskilde during development in the harbour-area in 1962 and 1996–97. The ship discovered in 1962, Skuldelev 2 is an oak-built Skeid longship. It is believed to have been built in the Dublin area around 1042. Skuldelev 2 could carry a crew of some 70–80 and measures just less than 30 m (98 feet) in length. They had around 30 rowing chairs. In 1996–97 archaeologists discovered the remains of another ship in the harbour. This ship, called the Roskilde 6, at 37 m (121 feet) is the longest Viking ship ever discovered and has been dated to around 1025.[11] Skuldelev 2 was replicated as Seastallion from Glendalough at the Viking Ship Museum in Roskilde and launched in 2004. In 2012, a 35-metre (115 ft) long skeid longship named Draken Harald Hårfagre was launched in Norway. It was built from scratch by experts, using original Viking and experimental archaeological methods.
Drakkar[edit]
Drakkar, or dreki[12] 'dragon', are the type of ship, of thirty rowing benches and upwards[13] that are only known from historical sources, such as the 13th-century Göngu-Hrólfs saga. Here, the ships are described as most unusual, elegant, ornately decorated, and used by those who went raiding and plundering. These ships were likely skeids that differed only in the carvings of menacing beasts, such as dragons and snakes, carried on the prow of the ship.[14]
The earliest mentioned drakkar was the ship of unstated size owned by Harald Fairhair in the tenth century.[15] The first drakkar ship whose size was mentioned in the source was Olav Tryggvason's thirty-room Tranin, built at Nidaros circa 995.[15] By far the most famous in this period was his later ship the Ormrinn Langi ('Long Serpent') of thirty-four rooms, built over the winter of 999 to 1000.[13] No true dragon ship, as described in the sagas, has been found by archaeological excavation.[15]
The city seal of Bergen, Norway, created in 1299,[12] depicts a ship with a dragon's head at either end, which might[16] be intended to represent a drakkar ship.
Construction[edit]
The first longships can trace their origin back to between 500 and 300 BC, when the Danish Hjortspring boat was built.[17] It was fastened with cord, not nailed, and paddled, not rowed. It had rounded cross sections and although 20 m (65 feet) long was only 2 m (6 feet) wide. The rounded sections gave maximum displacement for the lowest wetted surface area, similar to a modern narrow rowing skiff, so were very fast but had little carrying capacity. The shape suggests mainly river use. Unlike later boats, it had a low bow and stern. A distinctive feature is the two-prong cutaway bow section.
.JPG)
The earliest rowed true longship that has been found is the Nydam ship, built in Denmark around 350 AD. It also had very rounded underwater sections but had more pronounced flare in the topsides, giving it more stability as well as keeping more water out of the boat at speed or in waves. It had no sail. It was of lapstrake construction fastened with iron nails. The bow and stern had slight elevation. The keel was a flattened plank about twice as thick as a normal strake plank but still not strong enough to withstand the downwards thrust of a mast.
The Sutton Hoo longship, sometimes referred to as the ghost ship of the Wulflings, is about 27 m × 4.5 m (89 by 15 feet) maximum beam and built about 625 AD. It is associated with the Saxons. The ship was crushed by the weight of soil when buried but most details have been reconstructed. The ship was similar in hull section to the Nydam ship with flared topsides. Compared to later longships, the oak planks are wide—about 250 mm (9.8 inches) including laps, with less taper at bow and stern. Planks were 25 mm (0.98 inches) thick. The 26 heavy frames are spaced at 850 mm (33 inches) in the centre. Each frame tapers from the turn of the bilge to the inwale. This suggests that knees were used to brace the upper two or three topside planks but have rotted away. The hull had a distinctive leaf shape with the bow sections much narrower than the stern quarters. There were nine wide planks per side. The ship had a light keel plank but pronounced stem and stern deadwood. The reconstruction suggests the stern was much lower than the bow. It had a steering oar to starboard braced by an extra frame. The raised prow extended about 3.7 m (12 feet) above the keel and the hull was estimated to draw 750 mm (30 inches) when lightly laden. Between each futtock the planks were lapped in normal clinker style and fastened with six iron rivets per plank. There is no evidence of a mast, sail, or strengthening of the keel amidships but a half-sized replica, the Soe Wylfing, sailed very well with a modest sail area.
Sails started to be used from possibly the eighth century. The earliest had either plaited or chequered pattern, with narrow strips sewn together.[18]
In the late eighth century, the Kvalsund ship was built.[19] It is the first with a true keel. Its cross sectional shape was flatter on the bottom with less flare to the topsides. This shape is far more stable and able to handle rougher seas. It had the high prow of the later longships. After several centuries of evolution, the fully developed longship emerged some time in the middle of the ninth century. Its long, graceful, menacing head figure carved in the stern, such as the Oseburg ship, echoed the designs of its predecessors. The mast was now square in section and located toward the middle of the ship, and could be lowered and raised. The hull's sides were fastened together to allow it to flex with the waves, combining lightness and ease of handling on land. The ships were large enough to carry cargo and passengers on long ocean voyages, but still maintained speed and agility, making the longship a versatile warship and cargo carrier.
Keel, stems and hull[edit]
The Viking shipbuilders had no written diagrams or standard written design plan. The shipbuilder pictured the longship before its construction, based on previous builds, and the ship was then built from the keel up. The keel and stems were made first. The shape of the stem was based on segments of circles of varying sizes. The keel was an inverted T shape to accept the garboard planks. In the longships the keel was made up of several sections spliced together and fastened with treenails. The next step was building the strakes—the lines of planks joined endwise from stem to stern. Nearly all longships were clinker (also known as lapstrake) built, meaning that each hull plank overlapped the next. Each plank was hewn from an oak tree so that the finished plank was about 25 mm (0.98 inches) thick and tapered along each edge to a thickness of about 20 mm (0.79 inches). The planks were riven (radially hewn) so that the grain is approximately at right angles to the surface of the plank. This provides maximum strength, an even bend and an even rate of expansion and contraction in water. This is called in modern terms quartersawn timber, and has the least natural shrinkage of any cut section of wood. The plank above the turn of the bilge, the meginhufr, was about 37 mm (1.5 inches) thick on very long ships, but narrower to take the strain of the crossbeams. This was also the area subject to collisions. The planks overlapped by about 25–30 mm (0.98–1.18 in) and were joined by iron rivets. Each overlap was stuffed with wool or animal hair or sometimes hemp soaked in pine tar to ensure water tightness. Amidships, where the planks are straight, the rivets are about 170 mm (6.7 inches) apart, but they were closer together as the planks sweep up to the curved bow and stern. There is considerable twist and bend in the end planks. This was achieved by use of both thinner (by 50%) and narrower planks. In more sophisticated builds, forward planks were cut from natural curved trees called reaction wood. Planks were installed unseasoned or wet. Partly worked stems and sterns have been located in bogs. It has been suggested that they were stored there over winter to stop the wood from drying and cracking. The moisture in wet planks allowed the builder to force the planks into a more acute bend, if need be; once dry it would stay in the forced position. At the bow and the stern builders were able to create hollow sections, or compound bends, at the waterline, making the entry point very fine. In less sophisticated ships short and nearly straight planks were used at the bow and stern. Where long timber was not available or the ship was very long, the planks were butt-joined, although overlapping scarf joints fixed with nails were also used.
As the planks reached the desired height, the interior frame (futtocks) and cross beams were added. Frames were placed close together, which is an enduring feature of thin planked ships, still used today on some lightweight wooden racing craft such as those designed by Bruce Farr. Viking boat builders used a spacing of about 850 mm (33 inches). Part of the reason for this spacing was to achieve the correct distance between rowing stations and to create space for the chests used by Norse sailors as thwarts (seats). The bottom futtocks next to the keel were made from natural L-shaped crooks. The upper futtocks were usually not attached to the lower futtocks to allow some hull twist. The parts were held together with iron rivets, hammered in from the outside of the hull and fastened from the inside with a rove (washers). The surplus rivet was then cut off. A ship normally used about 700 kg (1,500 pounds) of iron nails in a 18 m (59 feet) long ship. In some ships the gap between the lower uneven futtock and the lapstrake planks was filled with a spacer block about 200 mm (7.9 inches) long. In later ships spruce stringers were fastened lengthwise to the futtocks roughly parallel to the keel. Longships had about five rivets for each yard (90 cm or 35 inches) of plank. In many early ships treenails (trenails, trunnels) were used to fasten large timbers. First, a hole about 20 mm (0.79 inches) wide hole was drilled through two adjoining timbers, a wooden pegs inserted which was split and a thin wedge inserted to expand the peg. Some treenails have been found with traces of linseed oil suggesting that treenails were soaked before the pegs were inserted. When dried the oil would act as a semi-waterproof weak filler/glue.
The longship's narrow deep keel provided strength beneath the waterline. A typical size keel of a longer ship was 100 mm × 300 mm (3.9 by 11.8 inches) amidships, tapering in width at the bow and stern. Sometimes there was a false outer keel to take the wear while being dragged up a beach. These large timbers were shaped with both adze and broadaxe. At the bow the cut water was especially strong, as longboats sailed in ice strewn water in spring. Hulls up to 560 cm (18.4 feet) wide gave stability, making the longship less likely to tip when sailed. The greater beam provided more moment of leverage by placing the crew or any other mobile weight on the windward side. Oceangoing longships had higher topsides about a 1 m (3.3 feet) high to keep out water. Higher topsides were supported with knees with the long axis fastened to the top of the crossbeams. The hull was waterproofed with animal hair, wool, hemp or moss drenched in pine tar. The ships would be tarred in the autumn and then left in a boathouse over the winter to allow time for the tar to dry. Evidence of small scale domestic tar production dates from between 100 AD and 400 AD. Larger industrial scale tar pits, estimated to be capable of producing up to 300 litres of tar in a single firing have been dated to between 680 AD and 900 AD.[20] A drain plug hole about 25 mm (0.98 inches) was drilled in the garboard plank on one side to allow rain water drainage.
The oars did not use rowlocks or thole pins but holes cut below the gunwale line. To keep seawater out, these oar holes were sealed with wooden disks from the inside, when the oars were not in use. The holes were also used for belaying mooring lines and sail sheets. At the bow the forward upper futtock protruded about 400 mm (16 inches) above the sheerline and was carved to retain anchor or mooring lines.
Timber[edit]
Analysis of timber samples from Viking long boats shows that a variety of timbers were used, but there was strong preference for oak, a tree associated with Thor in Viking mythology. Oak is a heavy, durable timber that can be easily worked by adze and axe when green (wet/unseasoned). Generally large and prestigious ships were made from oak. Other timber used were ash, elm, pine, spruce and larch. Spruce is light and seems to have been more common in later designs for internal hull battens (stringers). Although it is used for spars in modern times there is as yet no evidence the Vikings used spruce for masts. All timber was used unseasoned. The bark was removed by a bark spade. This consisted of a 1.2-metre long (3.9 ft) wooden handle with a T crossbar at the upper end, fitted with a broad chisel-like cutting edge of iron. The cutting edge was 60 mm (2.4 inches) wide and 80 mm (3.1 inches) long with a 120-millimetre long (4.7 in) neck where the handle was inserted. It appears that in cold winters wood work stopped and partly completed timber work was buried in mud to prevent it drying out. Timber was worked with iron adzes and axes. Most of the smoothing was done with a side axe. Other tools used in woodwork were hammers, wedges, drawknives, planes and saws. Iron saws were probably very rare. The Domesday Book in England (1086 AD) records only 13 saws. Possibly these were pit saws and it is uncertain if they were used in longship construction.
Sail and mast[edit]
Even though no longship sail has been found, accounts and depictions verify that longships had square sails. Sails measured perhaps 11 to 12 m (35 to 40 feet) across, and were made of rough wool cloth. Unlike in knarrs, a longship sail was not stitched.
The sail was held in place by the mast which was up to 16 m (52 feet) tall. Its base was about 250 mm × 180 mm (9.8 by 7.1 inches). The mast was supported by a large wooden maststep called a kerling ("old woman" in Old Norse) that was semicircular in shape. (Trent) The kerling was made of oak, and about 700 mm (28 inches) wide and up to 6 m (20 feet) long in the larger ships. It usually heavily tapered into a joint with the internal keelson, although keelsons were by no means universal. The kerling lay across two strong frames that ran width-wise above the keel in the centre of the boat. The kerling also had a companion: the "mast fish," a wooden timber above the kerling just below deck height that provided extra help in keeping the mast erect. It was a large wooden baulk of timber about 3 m (9.8 feet) long with a 1.4-metre long (4.6 ft) slot, facing aft to accommodate the mast as it was raised. This acted as a mechanism to catch and secure the mast before the stays were secured. It was an early form of mast partner but was aligned fore and aft. In later longships there is no mast fish—the mast partner is an athwartwise beam similar to more modern construction. Most masts were about half the length of the ship so that it did not project beyond the hull when unstepped. When lowered the mast foot was kept in the base of the mast step and the top of the mast secured in a natural wooden crook about 1.5–2.5 m (4 feet 11 inches – 8 feet 2 inches) high, on the port side, so that it did not interfere with steering on the starboard side.
There is a suggestion that the rig was sometimes used in a lateen style with the top cross spar dipped at an angle to aid sailing to windward i.e. the spar became the luff. There is little or no evidence to support this theory. No explanation is offered as to how this could be accomplished with a square sail as the lower reefed portion of the sail would be very bulky and would prevent even an approximation of the laminar flow necessary for windward sailing. There is no evidence of any triangular sails in use. Masts were held erect by side stays and possibly fore and aft stays. Each side stay was fitted at it lower end with a 150-millimetre long (5.9 in) toggle. There were no chain plates. The lower part of the side stay consisted of ropes looped under the end of a knee of upper futtock which had a hole underneath. The lower part of the stay was about 500–800 mm (1.6–2.6 feet) long and attached to a combined flat wooden turnblock and multi V jamb cleat called an angel (maiden, virgin). About four turns of rope went between the angel and the toggle to give the mechanical advantage to tighten the side stays. At each turn the v-shape at the bottom of the angels "wings" jambed the stay preventing slippage and movement.
Rudder[edit]
Early long boats used some form of steering oar but by the tenth century the side rudder (called a steerboard, the source for the etymology for the word starboard itself) was well established. It consisted of a length of timber about 2.4 m (7 feet 10 inches) long. The upper section was rounded to a diameter of about 150 mm (5.9 inches). The lower blade was about 1.8 m × 0.4 m (5 feet 11 inches by 1 foot 4 inches). The steerboard on the Gokstad ship in the Viking Ship Museum in Oslo, Norway, is about 20 cm (8 inches) wide, completely flat inboard and with about a 7.6 cm (3 inches) maximum width at the center of the foil. The head of the rudder shaft had two square holes about 200–300 mm (7.9–11.8 inches) apart. When the rudder was in its normal position the tiller was inserted in the upper hole so that the tiller faced athwartwise. The shaft was attached to the gunwale by a U shaped joint. Near the stern, about halfway down the starboard topsides, was a rounded wooden block about 150 mm (5.9 inches) in diameter and 100 mm (3.9 inches) high, with a central hole for a rope. This corresponded to a hole in the midsection of the rudder blade. From the outside the rope ran through the blade, through the round block and topsides and was fastened inside the hull. The flexibility of the hemp rope allowed the blade to pivot. When beached or in shallow water the tiller was moved to the lower hole, the blade rope was slackened and the rudder head pulled up so the rudder could operate in shallow waters. Modern facsimiles are reported to steer quite well but require a very large amount of physical effort compared to the modern fore and aft tiller.
Anchors[edit]
Longships for the most part used two different kinds of anchors. The most common was a natural wood yoke formed from a tree branch. The weight was supplied by a stone passing laterally through the U of the yoke. The top of the yoke was closed by either a length of hardwood or a curved iron head, which kept the stone in place. One side of the head stuck out so it could dig into mud or sand. In the Ladby ship burial in Denmark, a unique iron anchor has been found, resembling the modern fisherman's anchor but without the crossbar. The cross bar may have rusted away. This anchor—made of Norwegian iron—has a long iron chain to which the hemp warp was attached. This construction has several advantages when anchored in deep waters or in rough seas.[21]
Ship builders' toolkit[edit]
At the height of Viking expansion into Dublin and Jorvik 875–954 AD the longship reached a peak of development such as the Gokstad ship 890. Archaeological discoveries from this period at Coppergate, in York, show the shipwright had a large range of sophisticated woodwork tools. As well as the heavy adze, broad axe, wooden mallets and wedges, the craftsman had steel tools such as anvils, files, snips, awls, augers, gouges, draw knife, knives, including folding knives, chisels and small 300 mm (12 inches) long bow saws with antler handles. Edged tools were kept sharp with sharpening stones from Norway. One of the most sophisticated tools was a 25 mm (0.98 inches) diameter twist drill bit, perfect for drilling holes for treenails. Simple mechanical pole wood lathes were used to make cups and bowls.
Replica longships[edit]
Since the discovery of the original longships in the 1800s, many boat builders have built Viking ship replicas. However, most have not been able to resist the temptation to use more modern techniques and tools in the construction process. In 1892–93, a full-size near-replica of the Gokstad ship, the Viking, was built by the Norwegian Magnus Andersen in Bergen. It was used to sail the Atlantic. It had a deeper keel with a 1.5 m (4 feet 11 inches) draught to stiffen the hull, a range of non-authentic triangular sails to help performance, and big fenders on each gunwale filled with reindeer hair to give extra buoyancy in case of swamping. The skipper recorded that the keel bowed upwards as much as 20 mm (0.79 inches) and the gunwale flexed inwards as much as 150 mm (5.9 inches) in heavy seas.[22] A half-size replica of the Sutton Hoo longship has been equipped with a substantial sail, despite the original having oar power only. They took a year to make.[citation needed]
[edit]
[edit]
During the Viking Age (900–1200 AD) Vikings were the dominant seafarers of the North Atlantic. One of the keys to their success was the ability to navigate skillfully across the open waters.[23] The Vikings were experts in judging speed and wind direction, and in knowing the current and when to expect high and low tides. Viking navigational techniques are not well understood, but historians postulate that the Vikings probably had some sort of primitive astrolabe and used the stars to plot their course.
Viking Sundial
During an excavation of a Viking Age farm in southern Greenland part of a circular disk with carvings was recovered. The discovery of the so-called Viking Sundial suggested a hypothesis that it was used as a compass. Archaeologists found a piece of stone and a fragment of wooden disk both featuring straight and hyperbolic carvings. It turned out that the two items had been parts of sundials used by the Vikings as a compass during their sea-crossings along latitude 61 degrees North.[23]
Archaeologists have found two devices which they interpret as navigation instruments. Both appear to be sundialswith gnomon curves etched on a flat surface. The devices are small enough to be held flat in the hand at 70 mm (2.8 inches) diameter. A wooden version dated to about 1000 AD was found in Greenland. A stone version was also found at Vatnahverfi, Greenland. By looking at the place where the shadow from the rod falls on a carved curve, a navigator is able to sail along a line of latitude. Both gnomon curve devices show the curve for 61° north very prominently. This was the approximate latitude that the Vikings would have sailed along to get to Greenland from Scandinavia. The wooden device also has north marked and had 32 arrow heads around the edge that may be the points of a compass. Other lines are interpreted as the solstice and equinox curves. The device was tested successfully, as a sun compass, during a 1984 reenactment when a longship sailed across the North Atlantic. It was accurate to within ± 5°.[24]
Hypothesis
The Danish archaeologist Thorkild Ramskou suggested in 1967 that the "sun-stones" referred to in some sagas might have been natural crystals capable of polarizing skylight. The mineral cordierite occurring in Norway has the local name "Viking's Compass." Its changes in colour would allow determining the sun's position (azimuth) even through an overcast or foggy horizon.[25] The sunstones are doubly refracting, meaning that objects viewed through them can be seen as double because of positively charged calcium ions and negatively charged carbonate ions. When looking at the sun the stone, it will project two overlapping shadows on the crystal. The opacities of these shadows will vary depending on the sunstone's direction to the sun. When the two projected shapes have exactly the same opacity, it means the stone's long side is facing directly toward the sun. Since the stone uses light polarization, it works the best when the sun is at lower altitudes, or closer to the horizon. It makes sense that Norsemen were able to make use of sunstones, since much of the area they travelled and explored was near polar,[26] where the sun is very close to the horizon for a good amount of the year.[27] For example, in the Vinland sagas we see long voyages to North America, the majority sailed at over 61 degrees north.[23]
An ingenious navigation method is detailed in Viking Navigation Using the Sunstone, Polarized Light and the Horizon Board by Leif K. Karlsen.[28] To derive a course to steer relative to the sun direction, he uses a sun-stone (solarsteinn) made of Iceland spar (optical calcite or silfurberg), and a "horizon-board." The author constructed the latter from an Icelandic saga source, and describes an experiment performed to determine its accuracy. Karlsen also discusses why on North Atlantic trips the Vikings might have preferred to navigate by the sun rather than by stars, as at high latitudes in summer the days are long and the nights short.
A Viking named Stjerner Oddi compiled a chart showing the direction of sunrise and sunset, which enabled navigators to sail longships from place to place with ease. Almgren, an earlier Viking, told of another method: "All the measurements of angles were made with what was called a 'half wheel' (a kind of half sun-diameter which corresponds to about sixteen minutes of arc). This was something that was known to every skipper at that time, or to the long-voyage pilot or kendtmand ('man who knows the way') who sometimes went along on voyages ... When the sun was in the sky, it was not, therefore, difficult to find the four points of the compass, and determining latitude did not cause any problems either." (Almgren)[citation needed]
Birds provided a helpful guide to finding land. A Viking legend states that Vikings used to take caged crows aboard ships and let them loose if they got lost. The crows would instinctively head for land, giving the sailors a course to steer.
Propulsion[edit]
The longships had two methods of propulsion: oars and sail. At sea, the sail enabled longships to travel faster than by oar and to cover long distances overseas with far less manual effort. Sails could be raised or lowered quickly. In a modern facsimile the mast can be lowered in 90 seconds. Oars were used when near the coast or in a river, to gain speed quickly, and when there was an adverse (or insufficient) wind. In combat, the variability of wind power made rowing the chief means of propulsion. The ship was steered by a vertical flat blade with a short round handle, at right angles, mounted over the starboard side of the aft gunwale.
Longships were not fitted with benches. When rowing, the crew sat on sea chests (chests containing their personal possessions) that would otherwise take up space. The chests were made the same size and were the perfect height for a Viking to sit on and row. Longships had hooks for oars to fit into, but smaller oars were also used, with crooks or bends to be used as oarlocks. If there were no holes then a loop of rope kept the oars in place.
An innovation that improved the sail's performance was the beitaass, or stretching pole—a wooden spar stiffening the sail. The windward performance of the ship was poor by modern standards as there was no centreboard, deep keel or leeboard. To assist in tacking the beitaass kept the luff taut. Bracing lines were attached to the luff and led through holes on the forward gunwale. Such holes were often reinforced with short sections of timber about 500 to 700 mm (1.6 to 2.3 feet) long on the outside of the hull.
Legacy[edit]
The Vikings were major contributors to the shipbuilding technology of their day. Their shipbuilding methods spread through extensive contact with other cultures, and ships from the 11th and 12th centuries are known to borrow many of the longships' design features, despite the passing of many centuries.
Many historians, archaeologists and adventurers have reconstructed longships in an attempt to understand how they worked.[30] These re-creators have been able to identify many of the advances that the Vikings implemented in order to make the longship a superior vessel.
The longship was a master of all trades. It was wide and stable, yet light, fast, and nimble. With all these qualities combined in one ship, the longship was unrivalled for centuries, until the arrival of the great cog.
In Scandinavia, the longship was the usual vessel for war even with the introduction of cogs in the 12th–13th centuries. Leidang fleet-levy laws remained in place for most of the Middle Ages, demanding that the freemen should build, man, and furnish ships for war if demanded by the king—ships with at least 20 or 25 oar-pairs (40–50+ rowers). However, by the late 14th century, these low-boarded vessels were at a disadvantage against newer, taller vessels—when the Victual Brothers, in the employ of the Hansa, attacked Bergen in the autumn of 1393, the "great ships" of the pirates could not be boarded by the Norwegian levy ships called out by Margaret I of Denmark, and the raiders were able to sack the town with impunity. While earlier times had seen larger and taller longships in service, by this time the authorities had also gone over to other types of ships for warfare. The last Viking longship was defeated in 1429.
Notable longships[edit]
Preserved originals[edit]
Several of the original longships built in the Viking Age have been excavated by archaeologists. A selection of vessels that has been particularly important to our understanding of the longships design and construction, comprise the following:
- The Nydam ship (c. 310–320 AD) is a burial ship from Denmark. This oaken vessel is 24 m (80 feet) long and was propelled by oars only. No mast is attached, as it was a later addition to the longship design. The Nydam ship shows a combination of building styles and is important to our understanding of the evolution of the early Viking ships.
- "Puck 2" is the name given to a longship found in the Bay of Gdansk in Poland in 1977. It has been dated to the first half of the tenth century and was 19 to 20 metres (62 to 66 ft) long in its day. It is peculiar and important because it was constructed by Western Slavic craftsmen, not Scandinavian. The design only differs very slightly from the Scandinavian built longships.[31]
- Hedeby 1 is the name given to a longship found in the harbour of Hedeby in 1953. At nearly 31 metres (102 ft) long, it is of the Skeid type, built around 985 AD. With a maximum width of just 2.7 metres (8 ft 10 in) it has a width-to-length ratio of more than 11, making it the slimmest longship ever discovered. It is made of oaken wood and its construction would have required a very high level of craftsmanship.[32]
- The Oseberg ship and the Gokstad ship – both from Vestfold in Norway. They both represent the longship design of the later Viking Age.
- Roskilde 6 is the name given to the longest longship ever found at approximately 37.4 metres (123 ft). It was discovered in 1996–97 at the Viking Ship Museum in Roskilde, Denmark. The ship was constructed around 1025.[33]
- The Gjellestad ship, built in Norway around 732, was discovered in 2018. Excavations were completed in December 2022, and the remains of the keelare undergoing preservation.[34][35]
Historical examples[edit]
A selection of important longships known only from written sources includes:
- The Ormen Lange ("The Long Serpent") was the most famous longship of Norwegian king Olaf Tryggvason.
- The Mora was the ship given to William the Conqueror by his wife, Matilda, and used as the flagship in the Norman conquest of England. It is said to be of the drakar type.
- The Mariasuda, flagship of Norwegian king Sverre at the Battle of Fimreite, the largest recorded longship.
Replicas[edit]
There are many replicas of Viking ships – including longships – in existence. Some are just inspired by the longship design in general, while others are intricate works of experimental archaeology, trying to replicate the originals as accurately as possible. Replicas important to our understanding of the original longships design and construction include:
- Viking, the very first Viking ship replica, was built by the Rødsverven shipyard in Sandefjord, Norway, modelled after the Gokstad ship. In 1893, it sailed across the Atlantic Ocean to Chicago in The United States for the World's Columbian Exposition.
- The Skuldelev replicas. All the five Skuldelev ships have been replicated, some of them several times. They are each of a different design and only Skuldelev 1, 2 and 5 are longships.
- The Sea Stallion is a replica of the Skuldelev 2 ship, constructed by authentic methods. At 30 m (98 feet), it is the second longest Viking ship replica ever made. Skuldelev 2 was originally built near Dublin around 1042, and was rediscovered in Roskilde, Denmark in 1962. The Sea Stallion sailed from Roskilde to Dublin in summer 2007, to commemorate the voyage of the original.[30] In the winter 2007–2008, The Sea Stallion was exhibited outside the National Museum in Dublin. In the summer of 2008, the Sea Stallion returned to Roskilde on a searoute south of England.
- Dragon Harald Fairhair is the largest longship built in modern times at 35 m (115 feet). The ship is not a replica of any specific original longship, but was built by authentic construction methods. It was constructed in Haugesund, Norway and launched in 2012.
- The Íslendingur (Icelander) is a 22 m (72 feet) replica of the Gokstad ship that was built using traditional building techniques. In 2000, it was sailed from Iceland to L'Anse aux Meadows in Newfoundland, to participate in the 1000 year anniversary of Leif Erikson's discovery of America.[36]
- The Munin is a half-sized replica of the Gokstad ship. Berthed at the Vancouver Maritime Museum, she was built at the Scandinavian Community Centre, Burnaby, British Columbia and launched in 2001.[37][38]
- The Myklebust Ship is a 30 m replica of the original ship of the same name found in Nordfjordeid, Norway. The replica is situated in the Sagastadknowledge center, and is the largest longship ever discovered in Norway. The replica is the largest replica based on an original find. The replica was christened in 2019, as part of the opening of Sagastad.
Loch Ness Monster
 The "surgeon's photograph" of 1934, now known to have been a hoax[1] | |
| Sub grouping | Lake monster |
|---|---|
| Similar entities | Champ, Ogopogo, Altamaha-ha |
| First attested | 565[a] |
| Other name(s) | Nessie, Niseag |
| Country | Scotland |
| Region | Loch Ness, Scottish Highlands |
| Part of a series on the |
| Paranormal |
|---|
The Loch Ness Monster (Scottish Gaelic: Uilebheist Loch Nis),[3] affectionately known as Nessie, is a creature in Scottish folklore that is said to inhabit Loch Ness in the Scottish Highlands. It is often described as large, long-necked, and with one or more humps protruding from the water. Popular interest and belief in the creature has varied since it was brought to worldwide attention in 1933. Evidence of its existence is anecdotal with a number of disputed photographs and sonar readings.
The scientific community explains alleged sightings of the Loch Ness Monster as hoaxes, wishful thinking, and the misidentification of mundane objects.[4] The pseudoscience and subculture of cryptozoology has placed particular emphasis on the creature.
Origin of the name
In August 1933, the Courier published the account of George Spicer's alleged sighting. Public interest skyrocketed, with countless letters being sent in detailing different sightings[5] describing a "monster fish," "sea serpent," or "dragon,"[6] with the final name ultimately settling on "Loch Ness monster."[7] Since the 1940s, the creature has been affectionately called Nessie (Scottish Gaelic: Niseag).[8][9]
Sightings
Saint Columba (565)
The earliest report of a monster in the vicinity of Loch Ness appears in the Life of St. Columba by Adomnán, written in the seventh century AD.[10] According to Adomnán, writing about a century after the events described, Irish monk Saint Columba was staying in the land of the Picts with his companions when he encountered local residents burying a man by the River Ness. They explained that the man was swimming in the river when he was attacked by a "water beast" that mauled him and dragged him underwater despite their attempts to rescue him by boat. Columba sent a follower, Luigne moccu Min, to swim across the river. The beast approached him, but Columba made the sign of the cross and said: "Go no further. Do not touch the man. Go back at once."[11] The creature stopped as if it had been "pulled back with ropes" and fled, and Columba's men and the Picts gave thanks for what they perceived as a miracle.[11]
Believers in the monster point to this story, set in the River Ness rather than the loch itself, as evidence for the creature's existence as early as the sixth century.[12] Skeptics question the narrative's reliability, noting that water-beast stories were extremely common in medieval hagiographies, and Adomnán's tale probably recycles a common motif attached to a local landmark.[13] According to skeptics, Adomnán's story may be independent of the modern Loch Ness Monster legend and became attached to it by believers seeking to bolster their claims.[12] Ronald Binns considers that this is the most serious of various alleged early sightings of the monster, but all other claimed sightings before 1933 are dubious and do not prove a monster tradition before that date.[14] Christopher Cairney uses a specific historical and cultural analysis of Adomnán to separate Adomnán's story about St. Columba from the modern myth of the Loch Ness Monster, but finds an earlier and culturally significant use of Celtic "water beast" folklore along the way. In doing so he also discredits any strong connection between kelpies or water-horses and the modern "media-augmented" creation of the Loch Ness Monster. He also concludes that the story of Saint Columba may have been impacted by earlier Irish myths about the Caoránach and an Oilliphéist.[15]
D. Mackenzie (1871 or 1872)
In October 1871 (or 1872), D. Mackenzie of Balnain reportedly saw an object resembling a log or an upturned boat "wriggling and churning up the water," moving slowly at first before disappearing at a faster speed.[16][17] The account was not published until 1934, when Mackenzie sent his story in a letter to Rupert Gould shortly after popular interest in the monster increased.[18][17][19][20]
Alexander Macdonald (1888)
In 1888, mason Alexander Macdonald of Abriachan[21] sighted "a large stubby-legged animal" surfacing from the loch and propelling itself within fifty yards of the shore where Macdonald stood.[22] Macdonald reported his sighting to Loch Ness water bailiff Alex Campbell, and described the creature as looking like a salamander.[21]
Aldie Mackay (1933)
The best-known article that first attracted a great deal of attention about a creature was published on 2 May 1933 in The Inverness Courier, about a large "beast" or "whale-like fish". The article by Alex Campbell, water bailiff for Loch Ness and a part-time journalist,[citation needed] discussed a sighting by Aldie Mackay of an enormous creature with the body of a whale rolling in the water in the loch while she and her husband John were driving on the A82 on 15 April 1933. The word "monster" was reportedly applied for the first time in Campbell's article, although some reports claim that it was coined by editor Evan Barron.[14][23][24]
The Courier in 2017 published excerpts from the Campbell article, which had been titled "Strange Spectacle in Loch Ness".[25]
According to a 2013 article,[18] Mackay said that she had yelled, "Stop! The Beast!" when viewing the spectacle. In the late 1980s, a naturalist interviewed Aldie Mackay and she admitted to knowing that there had been an oral tradition of a "beast" in the loch well before her claimed sighting.[18] Alex Campbell's 1933 article also stated that "Loch Ness has for generations been credited with being the home of a fearsome-looking monster".[26]
George Spicer (1933)
Modern interest in the monster was sparked by a sighting on 22 July 1933, when George Spicer and his wife saw "a most extraordinary form of animal" cross the road in front of their car.[27] They described the creature as having a large body (about 4 feet (1.2 m) high and 25 feet (8 m) long) and a long, wavy, narrow neck, slightly thicker than an elephant's trunk and as long as the 10–12-foot (3–4 m) width of the road. They saw no limbs.[28] It lurched across the road toward the loch 20 yards (20 m) away, leaving a trail of broken undergrowth in its wake.[28] Spicer described it as "the nearest approach to a dragon or pre-historic animal that I have ever seen in my life,"[27] and as having "a long neck, which moved up and down in the manner of a scenic railway."[29] It had "an animal" in its mouth[27] and had a body that "was fairly big, with a high back, but if there were any feet they must have been of the web kind, and as for a tail I cannot say, as it moved so rapidly, and when we got to the spot it had probably disappeared into the loch."[29] Though he was the first to describe the creature as a plesiosaur-like dinosaur, evidence suggested by researchers at Columbia University in 2013 proved his story to be fake. The university and Daniel Loxton suggested that Spicer's sighting was fictionalized and inspired by a long-necked dinosaur that rises out of a lake in King Kong, a film that was extremely popular in theaters in his home city of London during August 1933, when Spicer reported the sighting.[30] Loxton and Donald Prothero later cited King Kong as evidently an influence on the Lock Ness Monster myth.[31]
On 4 August 1933 the Courier published a report of Spicer's sighting. This sighting triggered a massive amount of public interest and an uptick in alleged sightings, leading to the solidification of the actual name "Loch Ness Monster."[7]
It has been claimed that sightings of the monster increased after a road was built along the loch in early 1933, bringing workers and tourists to the formerly isolated area.[32] However, Binns has described this as "the myth of the lonely loch", as it was far from isolated before then, due to the construction of the Caledonian Canal. In the 1930s, the existing road by the side of the loch was given a serious upgrade.[14]
Hugh Gray (1933)
Hugh Gray's photograph taken near Foyers on 12 November 1933 was the first photograph alleged to depict the monster. It was slightly blurred, and it has been noted that if one looks closely the head of a dog can be seen. Gray had taken his Labrador for a walk that day and it is suspected that the photograph depicts his dog fetching a stick from the loch.[33] Others have suggested that the photograph depicts an otter or a swan. The original negative was lost. However, in 1963, Maurice Burton came into "possession of two lantern slides, contact positives from th[e] original negative" and when projected onto a screen they revealed an "otter rolling at the surface in characteristic fashion."[34]
Arthur Grant (1934)
On 5 January 1934 a motorcyclist, Arthur Grant, claimed to have nearly hit the creature while approaching Abriachan (near the north-eastern end of the loch) at about 1 a.m. on a moonlit night.[35] According to Grant, it had a small head attached to a long neck; the creature saw him, and crossed the road back to the loch. Grant, a veterinary student, described it as a cross between a seal and a plesiosaur. He said he dismounted and followed it to the loch, but saw only ripples.[21][36]
Grant produced a sketch of the creature that was examined by zoologist Maurice Burton, who stated it was consistent with the appearance and behavior of an otter.[37] Regarding the long size of the creature reported by Grant; it has been suggested that this was a faulty observation due to the poor light conditions.[38] Paleontologist Darren Naish has suggested that Grant may have seen either an otter or a seal and exaggerated his sighting over time.[39]
"Surgeon's photograph" (1934)
The "surgeon's photograph" is reportedly the first photo of the creature's head and neck.[40] Supposedly taken by Robert Kenneth Wilson, a London gynaecologist, it was published in the Daily Mail on 21 April 1934. Wilson's refusal to have his name associated with it led to it being known as the "surgeon's photograph".[41] According to Wilson, he was looking at the loch when he saw the monster, grabbed his camera and snapped four photos. Only two exposures came out clearly; the first reportedly shows a small head and back, and the second shows a similar head in a diving position. The first photo became well known, and the second attracted little publicity because of its blurriness.[citation needed]
For 60 years the photo was considered evidence of the monster's existence, although skeptics dismissed it as driftwood,[17] an elephant,[42] an otter or a bird. The photo's scale was controversial; it is often shown cropped (making the creature seem large and the ripples like waves), while the uncropped shot shows the other end of the loch and the monster in the centre. The ripples in the photo were found to fit the size and pattern of small ripples, rather than large waves photographed up close. Analysis of the original image fostered further doubt. In 1993, the makers of the Discovery Communicationsdocumentary Loch Ness Discovered analyzed the uncropped image and found a white object visible in every version of the photo (implying that it was on the negative). It was believed to be the cause of the ripples, as if the object was being towed, although the possibility of a blemish on the negative could not be ruled out. An analysis of the full photograph indicated that the object was small, about 60 to 90 cm (2 to 3 ft) long.[41]
Since 1994, most agree that the photo was an elaborate hoax.[41] It had been described as fake in a 7 December 1975 Sunday Telegraph article that fell into obscurity.[43] Details of how the photo was taken were published in the 1999 book, Nessie – the Surgeon's Photograph Exposed, which contains a facsimile of the 1975 Sunday Telegraph article.[44] The creature was reportedly a toy submarine built by Christian Spurling, the son-in-law of Marmaduke Wetherell. Wetherell had been publicly ridiculed by his employer, the Daily Mail, after he found "Nessie footprints" that turned out to be a hoax. To get revenge on the Mail, Wetherell perpetrated his hoax with co-conspirators Spurling (sculpture specialist), Ian Wetherell (his son, who bought the material for the fake), and Maurice Chambers (an insurance agent).[45] The toy submarine was bought from F. W. Woolworth, and its head and neck were made from wood putty. After testing it in a local pond the group went to Loch Ness, where Ian Wetherell took the photos near the Altsaigh Tea House. When they heard a water bailiff approaching, Duke Wetherell sank the model with his foot and it is "presumably still somewhere in Loch Ness".[17] Chambers gave the photographic plates to Wilson, a friend of his who enjoyed "a good practical joke". Wilson brought the plates to Ogston's, an Inverness chemist, and gave them to George Morrison for development. He sold the first photo to the Daily Mail,[46] who then announced that the monster had been photographed.[17]
Little is known of the second photo; it is often ignored by researchers, who believe its quality too poor and its differences from the first photo too great to warrant analysis. It shows a head similar to the first photo, with a more turbulent wave pattern, and possibly taken at a different time and location in the loch. Some believe it to be an earlier, cruder attempt at a hoax,[47] and others (including Roy Mackal and Maurice Burton) consider it a picture of a diving bird or otter that Wilson mistook for the monster.[16] According to Morrison, when the plates were developed, Wilson was uninterested in the second photo; he allowed Morrison to keep the negative, and the photo was rediscovered years later.[48] When asked about the second photo by the Ness Information Service Newsletter, Spurling "... was vague, thought it might have been a piece of wood they were trying out as a monster, but [was] not sure."[49]
Taylor film (1938)
On 29 May 1938, South African tourist G. E. Taylor filmed something in the loch for three minutes on 16 mm colour film. The film was obtained by popular science writer Maurice Burton, who did not show it to other researchers. A single frame was published in his 1961 book, The Elusive Monster. His analysis concluded it was a floating object, not an animal.[50]
William Fraser (1938)
On 15 August 1938, William Fraser, chief constable of Inverness-shire, wrote a letter that the monster existed beyond doubt and expressed concern about a hunting party that had arrived (with a custom-made harpoon gun) determined to catch the monster "dead or alive". He believed his power to protect the monster from the hunters was "very doubtful". The letter was released by the National Archives of Scotland on 27 April 2010.[51][52]
Sonar readings (1954)
In December 1954, sonar readings were taken by the fishing boat Rival III. Its crew noted a large object keeping pace with the vessel at a depth of 146 metres (479 ft). It was detected for 800 m (2,600 ft) before contact was lost and regained.[53] Previous sonar attempts were inconclusive or negative.
Peter MacNab (1955)
Peter MacNab at Urquhart Castle on 29 July 1955 took a photograph that depicted two long black humps in the water. The photograph was not made public until it appeared in Constance Whyte's 1957 book on the subject. On 23 October 1958 it was published by the Weekly Scotsman. Author Ronald Binns wrote that the "phenomenon which MacNab photographed could easily be a wave effect resulting from three trawlers travelling closely together up the loch."[54]
Other researchers consider the photograph a hoax.[55] Roy Mackal requested to use the photograph in his 1976 book. He received the original negative from MacNab, but discovered it differed from the photograph that appeared in Whyte's book. The tree at the bottom left in Whyte's was missing from the negative. It is suspected that the photograph was doctored by re-photographing a print.[56]
Dinsdale film (1960)
Aeronautical engineer Tim Dinsdale filmed a hump that left a wake crossing Loch Ness in 1960.[57] Dinsdale, who reportedly had the sighting on his final day of search, described it as reddish with a blotch on its side. He said that when he mounted his camera the object began to move, and he shot 40 feet of film. According to JARIC, the object was "probably animate".[58][third-party source needed] Others were sceptical, saying that the "hump" cannot be ruled out as being a boat[59] and when the contrast is increased, a man in a boat can be seen.[58]
In 1993 Discovery Communications produced a documentary, Loch Ness Discovered, with a digital enhancement of the Dinsdale film. A person who enhanced the film noticed a shadow in the negative that was not obvious in the developed film. By enhancing and overlaying frames, he found what appeared to be the rear body of a creature underwater: "Before I saw the film, I thought the Loch Ness Monster was a load of rubbish. Having done the enhancement, I'm not so sure".[60]
"Loch Ness Muppet" (1977)
On 21 May 1977 Anthony "Doc" Shiels, camping next to Urquhart Castle, took "some of the clearest pictures of the monster until this day".[citation needed]Shiels, a magician and psychic, claimed to have summoned the animal out of the water. He later described it as an "elephant squid", claiming the long neck shown in the photograph is actually the squid's "trunk" and that a white spot at the base of the neck is its eye. Due to the lack of ripples, it has been declared a hoax by a number of people and received its name because of its staged look.[61][62]
Holmes video (2007)
On 26 May 2007, 55-year-old laboratory technician Gordon Holmes videotaped what he said was "this jet black thing, about 14 metres (46 ft) long, moving fairly fast in the water."[63] Adrian Shine, a marine biologist at the Loch Ness 2000 Centre in Drumnadrochit, described the footage as among "the best footage [he had] ever seen."[63] BBC Scotland broadcast the video on 29 May 2007.[64] STV News North Tonight aired the footage on 28 May 2007 and interviewed Holmes. Shine was also interviewed, and suggested that the footage was an otter, seal or water bird.[65]
Sonar image (2011)
On 24 August 2011 Loch Ness boat captain Marcus Atkinson photographed a sonar image of a 1.5-metre-wide (4.9 ft), unidentified object that seemed to follow his boat for two minutes at a depth of 23 m (75 ft), and ruled out the possibility of a small fish or seal. In April 2012, a scientist from the National Oceanography Centre said that the image is a bloom of algae and zooplankton.[66]
George Edwards photograph (2011)
On 3 August 2012, skipper George Edwards claimed that a photo he took on 2 November 2011 shows "Nessie". Edwards claims to have searched for the monster for 26 years, and reportedly spent 60 hours per week on the loch aboard his boat, Nessie Hunter IV, taking tourists for rides on the lake.[67]Edwards said, "In my opinion, it probably looks kind of like a manatee, but not a mammal. When people see three humps, they're probably just seeing three separate monsters."[68]
Other researchers have questioned the photograph's authenticity,[69] and Loch Ness researcher Steve Feltham suggested that the object in the water is a fibreglass hump used in a National Geographic Channel documentary in which Edwards had participated.[70] Researcher Dick Raynor has questioned Edwards' claim of discovering a deeper bottom of Loch Ness, which Raynor calls "Edwards Deep". He found inconsistencies between Edwards' claims for the location and conditions of the photograph and the actual location and weather conditions that day. According to Raynor, Edwards told him he had faked a photograph in 1986 that he claimed was genuine in the Nat Geo documentary.[71] Although Edwards admitted in October 2013 that his 2011 photograph was a hoax,[72] he insisted that the 1986 photograph was genuine.[73]
A survey of the literature about other hoaxes, including photographs, published by The Scientific American on 10 July 2013, indicates many others since the 1930s. The most recent photo considered to be "good" appeared in newspapers in August 2012; it was allegedly taken by George Edwards in November 2011 but was "definitely a hoax" according to the science journal.[69]
David Elder video (2013)
On 27 August 2013, tourist David Elder presented a five-minute video of a "mysterious wave" in the loch. According to Elder, the wave was produced by a 4.5 m (15 ft) "solid black object" just under the surface of the water.[74] Elder, 50, from East Kilbride, South Lanarkshire, was taking a picture of a swan at the Fort Augustus pier on the south-western end of the loch,[75] when he captured the movement.[76] He said, "The water was very still at the time and there were no ripples coming off the wave and no other activity on the water."[76] Sceptics suggested that the wave may have been caused by a wind gust.[77]
Apple Maps photograph (2014)
On 19 April 2014, it was reported[78] that a satellite image on Apple Maps showed what appeared to be a large creature (thought by some to be the Loch Ness Monster) just below the surface of Loch Ness. At the loch's far north, the image appeared about 30 metres (98 ft) long. Possible explanations were the wake of a boat (with the boat itself lost in image stitching or low contrast), seal-caused ripples, or floating wood.[79][80]
Drone footage (2021)
In September 2021, it was reported that a 20-feet creature was captured on a live-stream near the loch.[81][82]
Searches
Edward Mountain expedition (1934)
After reading Rupert Gould's The Loch Ness Monster and Others,[21] Edward Mountain financed a search. Twenty men with binoculars and cameras positioned themselves around the loch from 9 am to 6 pm for five weeks, beginning on 13 July 1934. Although 21 photographs were taken, none was considered conclusive. Supervisor James Fraser remained by the loch filming on 15 September 1934; the film is now lost.[83] Zoologists and professors of natural history concluded that the film showed a seal, possibly a grey seal.[84]
Loch Ness Phenomena Investigation Bureau (1962–1972)
The Loch Ness Phenomena Investigation Bureau (LNPIB) was a UK-based society formed in 1962 by Norman Collins, R. S. R. Fitter, politician David James, Peter Scott and Constance Whyte[85] "to study Loch Ness to identify the creature known as the Loch Ness Monster or determine the causes of reports of it".[86] In 1967 it received a grant of $20,000 from World Book Encyclopedia to fund a 2-year programme of daylight watches from May to October. The principal equipment was 35 mm movie cameras on mobile units with 20 inch lenses, and one with a 36 inch lens at Achnahannet, near the midpoint of the loch. With the mobile units in laybys about 80% of the loch surface was covered.[87] The society's name was later shortened to the Loch Ness Investigation Bureau (LNIB), and it disbanded in 1972.[88] The LNIB had an annual subscription charge, which covered administration. Its main activity was encouraging groups of self-funded volunteers to watch the loch from vantage points with film cameras with telescopic lenses. From 1965 to 1972 it had a caravan camp and viewing platform at Achnahannet, and sent observers to other locations up and down the loch.[89][90] According to the bureau's 1969 annual report[91] it had 1,030 members, of whom 588 were from the UK.
Sonar study (1967–1968)
D. Gordon Tucker, chair of the Department of Electronic and Electrical Engineering at the University of Birmingham, volunteered his services as a sonar developer and expert at Loch Ness in 1968.[92] His gesture, part of a larger effort led by the LNPIB from 1967 to 1968, involved collaboration between volunteers and professionals in a number of fields. Tucker had chosen Loch Ness as the test site for a prototype sonar transducer with a maximum range of 800 m (2,600 ft). The device was fixed underwater at Temple Pier in Urquhart Bay and directed at the opposite shore, drawing an acoustic "net" across the loch through which no moving object could pass undetected. During the two-week trial in August, multiple targets were identified. One was probably a shoal of fish, but others moved in a way not typical of shoals at speeds up to 10 knots.[93]
Robert Rines studies (1972, 1975, 2001, 2008)
In 1972, a group of researchers from the Academy of Applied Science led by Robert H. Rines conducted a search for the monster involving sonar examination of the loch depths for unusual activity. Rines took precautions to avoid murky water with floating wood and peat.[citation needed] A submersible camera with a floodlight was deployed to record images below the surface. If Rines detected anything on the sonar, he turned the light on and took pictures.
On 8 August, Rines' Raytheon DE-725C sonar unit, operating at a frequency of 200 kHz and anchored at a depth of 11 metres (36 ft), identified a moving target (or targets) estimated by echo strength at 6 to 9 metres (20 to 30 ft) in length. Specialists from Raytheon, Simrad (now Kongsberg Maritime), Hydroacoustics, Marty Klein of MIT and Klein Associates (a side-scan sonar producer) and Ira Dyer of MIT's Department of Ocean Engineering were on hand to examine the data. P. Skitzki of Raytheon suggested that the data indicated a 3-metre (10 ft) protuberance projecting from one of the echoes. According to author Roy Mackal, the shape was a "highly flexible laterally flattened tail" or the misinterpreted return from two animals swimming together.[94]
Concurrent with the sonar readings, the floodlit camera obtained a pair of underwater photographs. Both depicted what appeared to be a rhomboid flipper, although sceptics have dismissed the images as depicting the bottom of the loch, air bubbles, a rock, or a fish fin. The apparent flipper was photographed in different positions, indicating movement.[95] The first flipper photo is better-known than the second, and both were enhanced and retouched from the original negatives. According to team member Charles Wyckoff, the photos were retouched to superimpose the flipper; the original enhancement showed a considerably less-distinct object. No one is sure how the originals were altered.[96] During a meeting with Tony Harmsworth and Adrian Shine at the Loch Ness Centre & Exhibition, Rines admitted that the flipper photo may have been retouched by a magazine editor.[97]
British naturalist Peter Scott announced in 1975, on the basis of the photographs, that the creature's scientific name would be Nessiteras rhombopteryx(Greek for "Ness inhabitant with diamond-shaped fin").[98][99] Scott intended that the name would enable the creature to be added to the British register of protected wildlife. Scottish politician Nicholas Fairbairn called the name an anagram for "Monster hoax by Sir Peter S".[100][101][102] However, Rines countered that when rearranged, the letters could also spell "Yes, both pix are monsters – R."[100]
Another sonar contact was made, this time with two objects estimated to be about 9 metres (30 ft). The strobe camera photographed two large objects surrounded by a flurry of bubbles.[103] Some interpreted the objects as two plesiosaur-like animals, suggesting several large animals living in Loch Ness. This photograph has rarely been published.
A second search was conducted by Rines in 1975. Some of the photographs, despite their obviously murky quality and lack of concurrent sonar readings, did indeed seem to show unknown animals in various positions and lightings. One photograph appeared to show the head, neck, and upper torso of a plesiosaur-like animal,[103] but sceptics argue the object is a log due to the lump on its "chest" area, the mass of sediment in the full photo, and the object's log-like "skin" texture.[97] Another photograph seemed to depict a horned "gargoyle head", consistent with that of some sightings of the monster;[103]however, sceptics point out that a tree stump was later filmed during Operation Deepscan in 1987, which bore a striking resemblance to the gargoyle head.[97]
In 2001, Rines' Academy of Applied Science videotaped a V-shaped wake traversing still water on a calm day. The academy also videotaped an object on the floor of the loch resembling a carcass and found marine clamshells and a fungus-like organism not normally found in freshwater lochs, a suggested connection to the sea and a possible entry for the creature.[104]
In 2008, Rines theorised that the creature may have become extinct, citing the lack of significant sonar readings and a decline in eyewitness accounts. He undertook a final expedition, using sonar and an underwater camera in an attempt to find a carcass. Rines believed that the animals may have failed to adapt to temperature changes resulting from global warming.[105]
Operation Deepscan (1987)
Operation Deepscan was conducted in 1987.[106] Twenty-four boats equipped with echo sounding equipment were deployed across the width of the loch, and simultaneously sent acoustic waves. According to BBC News the scientists had made sonar contact with an unidentified object of unusual size and strength.[107] The researchers returned, re-scanning the area. Analysis of the echosounder images seemed to indicate debris at the bottom of the loch, although there was motion in three of the pictures. Adrian Shine speculated, based on size, that they might be seals that had entered the loch.[108]
Sonar expert Darrell Lowrance, founder of Lowrance Electronics, donated a number of echosounder units used in the operation. After examining a sonar return indicating a large, moving object at a depth of 180 metres (590 ft) near Urquhart Bay, Lowrance said: "There's something here that we don't understand, and there's something here that's larger than a fish, maybe some species that hasn't been detected before. I don't know."[109]
Searching for the Loch Ness Monster (2003)
In 2003, the BBC sponsored a search of the loch using 600 sonar beams and satellite tracking. The search had sufficient resolution to identify a small buoy. No animal of substantial size was found and, despite their reported hopes, the scientists involved admitted that this proved the Loch Ness Monster was a myth. Searching for the Loch Ness Monster aired on BBC One.[110]
DNA survey (2018)
An international team consisting of researchers from the universities of Otago, Copenhagen, Hull and the Highlands and Islands, did a DNA survey of the lake in June 2018, looking for unusual species.[111] The results were published in 2019; no DNA of large fish such as sharks, sturgeons and catfish could be found. No otter or seal DNA were obtained either, though there was a lot of eel DNA. The leader of the study, Prof Neil Gemmell of the University of Otago, said he could not rule out the possibility of eels of extreme size, though none were found, nor were any ever caught. The other possibility is that the large amount of eel DNA simply comes from many small eels. No evidence of any reptilian sequences were found, he added, "so I think we can be fairly sure that there is probably not a giant scaly reptile swimming around in Loch Ness", he said.[112][113]
Explanations
A number of explanations have been suggested to account for sightings of the creature. According to Ronald Binns, a former member of the Loch Ness Phenomena Investigation Bureau, there is probably no single explanation of the monster. Binns wrote two sceptical books, the 1983 The Loch Ness Mystery Solved, and his 2017 The Loch Ness Mystery Reloaded. In these he contends that an aspect of human psychology is the ability of the eye to see what it wants, and expects, to see.[14] They may be categorised as misidentifications of known animals, misidentifications of inanimate objects or effects, reinterpretations of Scottish folklore, hoaxes, and exotic species of large animals. A reviewer wrote that Binns had "evolved into the author of ... the definitive, skeptical book on the subject". Binns does not call the sightings a hoax, but "a myth in the true sense of the term" and states that the "'monster is a sociological ... phenomenon. ...After 1983 the search ... (for the) possibility that there just might be continues to enthrall a small number for whom eye-witness evidence outweighs all other considerations".[114]
Misidentification of known animals
Eels
A large eel was an early suggestion for what the "monster" was. Eels are found in Loch Ness, and an unusually large one would explain many sightings.[115] Dinsdale dismissed the hypothesis because eels undulate side to side like snakes.[116] Sightings in 1856 of a "sea-serpent" (or kelpie) in a freshwater lake near Leurbost in the Outer Hebrides were explained as those of an oversized eel, also believed common in "Highland lakes".[117] From 2018 to 2019, scientists from New Zealand undertook a massive project to document every organism in Loch Ness based on DNA samples. Their reports confirmed that European eels are still found in the Loch. No DNA samples were found for large animals such as catfish, Greenland sharks, or plesiosaurs. Many scientists now believe that giant eels account for many, if not most of the sightings.[118][119][120][121]
Elephant
In a 1979 article, California biologist Dennis Power and geographer Donald Johnson claimed that the "surgeon's photograph" was the top of the head, extended trunk and flared nostrils of a swimming elephant photographed elsewhere and claimed to be from Loch Ness.[42] In 2006, palaeontologist and artist Neil Clark suggested that travelling circuses might have allowed elephants to bathe in the loch; the trunk could be the perceived head and neck, with the head and back the perceived humps. In support of this, Clark provided an example painting.[122]
Greenland shark
Zoologist, angler and television presenter Jeremy Wade investigated the creature in 2013 as part of the series River Monsters, and concluded that it is a Greenland shark. The Greenland shark, which can reach up to 20 feet in length, inhabits the North Atlantic Ocean around Canada, Greenland, Iceland, Norway, and possibly Scotland. It is dark in colour, with a small dorsal fin.[123] According to biologist Bruce Wright, the Greenland shark could survive in fresh water (possibly using rivers and lakes to find food) and Loch Ness has an abundance of salmon and other fish.[124][125]
Wels catfish
In July 2015 three news outlets reported that Steve Feltham, after a vigil at the loch that was recognized by the Guinness Book of Records, theorised that the monster is an unusually large specimen of Wels catfish (Silurus glanis), which may have been released during the late 19th century.[126][127][128]
Other resident animals
It is difficult to judge the size of an object in water through a telescope or binoculars with no external reference. Loch Ness has resident otters, and photos of them and deer swimming in the loch, which were cited by author Ronald Binns[129] may have been misinterpreted. According to Binns, birds may be mistaken for a "head and neck" sighting.[130]
Misidentifications of inanimate objects or effects
Boat wakes
Wakes have been reported when the loch is calm, with no boats nearby. Bartender David Munro reported a wake he believed was a creature zigzagging, diving, and reappearing; there were reportedly 26 other witnesses from a nearby car park.[96][better source needed] Although some sightings describe a V-shaped wake similar to a boat's,[104] others report something not conforming to the shape of a boat.[60]
Trees
In 1933, the Daily Mirror published a picture with the caption: "This queerly-shaped tree-trunk, washed ashore at Foyers [on Loch Ness] may, it is thought, be responsible for the reported appearance of a 'Monster'".[131] In a 1982 series of articles for New Scientist, Maurice Burton proposed that sightings of Nessie and similar creatures may be fermenting Scots pine logs rising to the surface of the loch. A decomposing log could not initially release gases caused by decay because of its high resin level. Gas pressure would eventually rupture a resin seal at one end of the log, propelling it through the water (sometimes to the surface). According to Burton, the shape of tree logs (with their branch stumps) closely resembles descriptions of the monster.[132][133][134]
Seiches and wakes
Loch Ness, because of its long, straight shape, is subject to unusual ripples affecting its surface. A seiche is a large oscillation of a lake, caused by water reverting to its natural level after being blown to one end of the lake (resulting in a standing wave); the Loch Ness oscillation period is 31.5 minutes.[135]Earthquakes in Scotland are too weak to cause observable seiches, but extremely massive earthquakes far away could cause large waves. The seiche created in Loch Ness by the catastrophic 1755 Lisbon earthquake was reportedly "so violent as to threaten destruction to some houses built on the sides of it", while the 1761 aftershock caused two-foot (60 cm) waves. However, no sightings of the monster were reported in 1755.[136][137]
Optical effects
Wind conditions can give a choppy, matte appearance to the water with calm patches appearing dark from the shore (reflecting the mountains and clouds).[138] In 1979 W. H. Lehn showed that atmospheric refraction could distort the shape and size of objects and animals,[139] and later published a photograph of a mirage of a rock on Lake Winnipeg that resembled a head and neck.[140]
Seismic gas
Italian geologist Luigi Piccardi has proposed geological explanations for ancient legends and myths. Piccardi noted that in the earliest recorded sighting of a creature (the Life of Saint Columba), the creature's emergence was accompanied "cum ingenti fremitu" ("with loud roaring"). The Loch Ness is along the Great Glen Fault, and this could be a description of an earthquake. Many reports consist only of a large disturbance on the surface of the water; this could be a release of gas through the fault, although it may be mistaken for something swimming below the surface.[141]
Folklore
In 1980 Swedish naturalist and author Bengt Sjögren wrote that present beliefs in lake monsters such as the Loch Ness Monster are associated with kelpielegends. According to Sjögren, accounts of loch monsters have changed over time; originally describing horse-like creatures, they were intended to keep children away from the loch. Sjögren wrote that the kelpie legends have developed into descriptions reflecting a modern awareness of plesiosaurs.[142]
The kelpie as a water horse in Loch Ness was mentioned in an 1879 Scottish newspaper,[143] and inspired Tim Dinsdale's Project Water Horse.[144] A study of pre-1933 Highland folklore references to kelpies, water horses and water bulls indicated that Ness was the loch most frequently cited.[145]
Hoaxes
A number of hoax attempts have been made, some of which were successful. Other hoaxes were revealed rather quickly by the perpetrators or exposed after diligent research. A few examples follow.
In August 1933, Italian journalist Francesco Gasparini submitted what he said was the first news article on the Loch Ness Monster. In 1959, he reported sighting a "strange fish" and fabricated eyewitness accounts: "I had the inspiration to get hold of the item about the strange fish. The idea of the monster had never dawned on me, but then I noted that the strange fish would not yield a long article, and I decided to promote the imaginary being to the rank of monster without further ado."[146]
In the 1930s, big-game hunter Marmaduke Wetherell went to Loch Ness to look for the monster. Wetherell claimed to have found footprints, but when casts of the footprints were sent to scientists for analysis they turned out to be from a hippopotamus; a prankster had used a hippopotamus-foot umbrella stand.[147]
In 1972 a team of zoologists from Yorkshire's Flamingo Park Zoo, searching for the monster, discovered a large body floating in the water. The corpse, 4.9–5.4 m (16–18 ft) long and weighing as much as 1.5 tonnes, was described by the Press Association as having "a bear's head and a brown scaly body with clawlike fins." The creature was placed in a van to be carried away for testing, but police seized the cadaver under an act of parliament prohibiting the removal of "unidentified creatures" from Loch Ness. It was later revealed that Flamingo Park education officer John Shields shaved the whiskers and otherwise disfigured a bull elephant seal that had died the week before and dumped it in Loch Ness to dupe his colleagues.[148]
On 2 July 2003, Gerald McSorely discovered a fossil, supposedly from the creature, when he tripped and fell into the loch. After examination, it was clear that the fossil had been planted.[149]
In 2004 a Five TV documentary team, using cinematic special-effects experts, tried to convince people that there was something in the loch. They constructed an animatronic model of a plesiosaur, calling it "Lucy". Despite setbacks (including Lucy falling to the bottom of the loch), about 600 sightings were reported where she was placed.[150][151]
In 2005, two students claimed to have found a large tooth embedded in the body of a deer on the loch shore. They publicised the find, setting up a website, but expert analysis soon revealed that the "tooth" was the antler of a muntjac. The tooth was a publicity stunt to promote a horror novel by Steve Alten, The Loch.[149]
Exotic large-animal species
 | This article may lend undue weight to fringe sources and hypotheses. (July 2023) |
Plesiosaur
In 1933 it was suggested that the creature "bears a striking resemblance to the supposedly extinct plesiosaur",[152]a long-necked aquatic reptile that became extinct during the Cretaceous–Paleogene extinction event. A popular explanation at the time, the following arguments have been made against it:
- In an October 2006 New Scientist article, "Why the Loch Ness Monster is no plesiosaur", Leslie Noè of the Sedgwick Museum in Cambridge said: "The osteology of the neck makes it absolutely certain that the plesiosaur could not lift its head up swan-like out of the water".[153]
- The loch is only about 10,000 years old, dating to the end of the last ice age. Before then, it was frozen for about 20,000 years.[154]
- If creatures similar to plesiosaurs lived in Loch Ness they would be seen frequently, since they would have to surface several times a day to breathe.[108]
In response to these criticisms, Tim Dinsdale, Peter Scott and Roy Mackal postulate a trapped marine creature that evolved from a plesiosaur directly or by convergent evolution.[155] Robert Rines explained that the "horns" in some sightings function as breathing tubes (or nostrils), allowing it to breathe without breaking the surface. Also new discoveries have shown that Plesiosaurs had the ability to swim in fresh waters, but the cold temperatures would make it hard for it to live.
Long-necked giant amphibian
R. T. Gould suggested a long-necked newt;[21][156] Roy Mackal examined the possibility, giving it the highest score (88 percent) on his list of possible candidates.[157]
Invertebrate
In 1968 F. W. Holiday proposed that Nessie and other lake monsters, such as Morag, may be a large invertebrate such as a bristleworm; he cited the extinct Tullimonstrum as an example of the shape.[158] According to Holiday, this explains the land sightings and the variable back shape; he likened it to the medieval description of dragons as "worms". Although this theory was considered by Mackal, he found it less convincing than eels, amphibians or plesiosaurs.[159]
Leopard seal
| Leopard seal[1] Temporal range: Early Pliocene – Recent | |
|---|---|
_04.jpg) | |
| At the Antarctic Sound, near Brown Bluff, Tabarin Peninsula | |
 | |
| Size compared to a 1.82 m (6ft) human | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Carnivora |
| Clade: | Pinnipedia |
| Family: | Phocidae |
| Subfamily: | Monachinae |
| Tribe: | Lobodontini |
| Genus: | Hydrurga Gistel, 1848 |
| Species: | H. leptonyx |
| Binomial name | |
| Hydrurga leptonyx (Blainville, 1820) | |
 | |
| Hydrurga leptonyx range map | |
| Synonyms | |
| |
The leopard seal (Hydrurga leptonyx), also referred to as the sea leopard,[3] is the second largest species of seal in the Antarctic (after the southern elephant seal). Its only natural predator is the orca.[4] It feeds on a wide range of prey including cephalopods, other pinnipeds, krill, fish, and birds, particularly penguins. It is the only species in the genus Hydrurga. Its closest relatives are the Ross seal, the crabeater seal and the Weddell seal, which together are known as the tribe of Lobodontini seals.[5][6] The name hydrurga means "water worker" and leptonyx is the Greek for "thin-clawed".
Taxonomy[edit]
French zoologist Henri Marie Ducrotay de Blainville described the leopard seal in 1820.
Description[edit]
The leopard seal has a distinctively long and muscular body shape when compared to other seals. The overall length of adults is 2.4–3.5 m (7.9–11.5 ft) and weight is from 200 to 600 kilograms (440 to 1,320 lb) making them the same length as the northern walrus but usually less than half the weight.[7][8] Females are slightly larger than males.[9]
It is perhaps best known for its massive jaws, which allow it to be one of the top predators in its environment.[10] The front teeth are sharp like those of other carnivores, but their molars lock together in a way that allows them to sieve krill from the water in the manner of the crabeater seal. The coat is counter-shaded with a silver to dark gray blend and a distinctive spotted "leopard" coloration pattern dorsally and a paler, white to light gray color ventrally.[10] The whiskers are short and clear.
As "true" seals, they do not have external ears or pinnae, but possess an internal ear canal that leads to an external opening.[11] Their hearing in air is similar to that of a human, but scientists have noted that leopard seals use their ears in conjunction with their whiskers to track prey under water.[11]
Distribution[edit]
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Leopard seals are pagophilic ("ice-loving") seals, which primarily inhabit the Antarctic pack ice between 50˚S and 80˚S. Sightings of vagrant leopard seals have been recorded on the coasts of Australia, New Zealand (where individuals have been seen even on the foreshores of major cities such as Auckland,[12] Dunedin[13] and Wellington[14]), South America, and South Africa.[11] In August 2018, an individual was sighted at Geraldton, on the west coast of Australia. Higher densities of leopard seals are seen in the Western Antarctic than in other regions.[15][16]
Most leopard seals remain within the pack ice throughout the year and remain solitary during most of their lives with the exception of a mother and her newborn pup.[17][11][18] These matrilineal groups can move further north in the austral winter to sub-antarctic islands and the coastlines of the southern continents to provide care for their pups.[11] While solitary animals may appear in areas of lower latitudes, females rarely breed there. Some researchers believe this is due to safety concerns for the pups.[19] Lone male leopard seals hunt other marine mammals and penguins in the pack ice of antarctic waters. The estimated population of this species ranges from 220,000 to 440,000 individuals, putting leopard seals at "least concern".[11] Although there is an abundance of leopard seals in the Antarctic, they are difficult to survey by traditional audiovisual techniques[20] as they spend long periods of time vocalizing under the water’s surface during the austral spring and summer, when audiovisual surveys are carried out. The habit of submarine vocalizing makes leopard seals naturally suited for acoustic surveys, as are conducted with cetaceans, allowing researchers to gather most of what is known about them.[21]
Behavior[edit]
_05.jpg)
Acoustic behavior[edit]
Leopard seals are very vocal underwater during the austral summer.[21]The male seals produce loud calls (153 to 177 dB re 1 μPa at 1 m) for many hours each day.[22] While singing the seal hangs upside down and rocks from side to side under the water. Their back is bent, the neck and cranial thoracic region (the chest) is inflated and as they call their chest pulses. The male calls can be split into two categories: vocalizing and silencing, in which vocalizing is when they are making noises underwater, and silencing noted as the breathing period at the air surface.[23] Adult male leopard seals have only a few stylized calls, some are like bird or cricket-like trills yet others are low haunting moans.[24] Scientists have identified five distinctive sounds that male leopard seals make, which include: the high double trill, medium single trill, low descending trill, low double trill, and a hoot with a single low trill. These cadence of calls are believed to be a part of a long range acoustic display for territorial purposes, or the attraction of a potential mate.[23]
The leopard seals have age-related differences in their calling patterns, just like birds. Where the younger male seals have many different types of variable calls – the adult male seals have only a few, highly stylized calls.[25] Each male leopard seal produces these individual calls, and can arrange their few call types into individually distinctive sequences (or songs).[26] The acoustic behavior of the leopard seal is believed to be linked to their breeding behaviour. In male seals, vocalizing coincides with the timing of their breeding season, which falls between November and the first week of January; captive female seals vocalize when they have elevated reproductive hormones.[24] Conversely, a female leopard seal can attribute calls to their environment as well; however, usually it is to gain the attention of a pup, after getting back from a forage for food.
Breeding habits[edit]
.jpg)
Since leopard seals live in an area difficult for humans to survive in, not much is known on their reproduction and breeding habits. However, it is known that their breeding system is polygynous, meaning that males mate with multiple females during the mating period. A sexually active female (ages 3–7) can give birth to a single pup during the summer on the floating ice floes of the Antarctic pack ice, with a sexually active male (ages 6–7). Mating occurs from December to January, shortly after the pups are weaned when the female seal is in estrus.[27] In preparation for the pups, the females dig a circular hole in the ice as a home for the pup. A newborn pup weighs around 66 pounds and are usually with their mother for a month, before they are weaned off. The male leopard seal does not participate in taking care of the pup, and goes back to its solitary lifestyle after the breeding season.[11] Most leopard seal breeding is on pack ice.[28]
Five research voyages were made to Antarctica in 1985, 1987 and 1997–1999 to look at leopard seals.[28] They sighted seal pups from the beginning of November to the end of December, and noticed that there was about one pup for every three adults, and they also noticed that most of the adults were staying away from other adults during this season, and when they were seen in groups they showed no sign of interaction.[29] Leopard seal pups mortality rate within the first year is close to 25%.[30]
Vocalization is thought to be important in breeding, since males are much more vocal around this time. Mating takes place in the water, and then the male leaves the female to care for the pup, which the female gives birth to after an average gestation period of 274 days.[27]
Research shows that on average, the aerobic dive limit for juvenile seals is around 7 minutes, which means that during the winter months juvenile leopard seals do not eat krill, which is a major part of older seals' diets, since krill is found deeper during this time.[31] This might occasionally lead to co-operative hunting. Co-operative hunting of leopard seals on Antarctic fur seal pups has been witnessed, which could be a mother helping her older pup, or could also be female-male couple interactions, to increase their hunting productivity.[32]
Foraging behavior[edit]
The only natural predator of leopard seals is the orca.[4] The seal's canine teeth are up to 2.5 cm (1 in) long.[33] It feeds on a wide variety of creatures. Young leopard seals usually eat mostly krill, squid and fish. Adult seals probably switch from krill to more substantial prey, including king, Adélie, rockhopper, gentoo, emperor and chinstrap penguins, and less frequently, Weddell, crabeater, Ross, and young southern elephant seals. Leopard seals are also known to take fur seal pups.[34]
Around the sub-Antarctic island of South Georgia, the Antarctic fur seal(Arctocephalus gazella) is the main prey. Other prey include penguins and fish including chondrichthyans.[35] Antarctic krill (Euphausia superba), southern elephant seal (Mirounga leonina) pups and seabirds other than penguins have also been taken as prey.[36]
When hunting penguins, the leopard seal patrols the waters near the edges of the ice, almost completely submerged, waiting for the birds to enter the ocean. It kills the swimming bird by grabbing the feet, then shaking the penguin vigorously and beating its body against the surface of the water repeatedly until the penguin is dead. Previous reports stating the leopard seal skins its prey before feeding have been found to be incorrect. Lacking the teeth necessary to slice its prey into manageable pieces, it flails its prey from side to side tearing and ripping it into smaller pieces. Krill meanwhile, is eaten by suction, and strained through the seal's teeth, allowing leopard seals to switch to different feeding styles. Such generalization and adaptations may be responsible for the seal's success in the challenging Antarctic ecosystem.[37]
Physiology and research[edit]
Leopard seals' heads and front flippers are extremely large in comparison to other phocids. Their large front flippers are used to steer themselves through the water column making them extremely agile while hunting. They use their front flippers similarly to sea lions (otariids)[38] and leopard seal females are larger than males.[39] They are covered in a thick layer of blubber that helps to keep them warm while in the cold temperatures of the Antarctic. This layer of blubber also helps to streamline their body making them more hydrodynamic. This is essential when hunting small prey items such as penguins because speed is necessary. Scientists take blubber thickness, girth, weight, and length measurements of leopard seals to learn about their average weight, health, and population as a whole.[40] These measurements are then used to calculate their energetics which is the amount of energy and food it takes for them to survive as a species. They also have incredible diving capabilities. This information can be obtained by scientists by attaching transmitters to the seals after they are tranquilized on the ice. These devices are called satellite-linked time depth recorders (SLDRs) and time-depth recorders (TDRs). Scientists attach this device usually to the head of the animal and it records depth, bottom time, total dive time, date and time, surface time, haul out time, pitch and roll, and total number of dives.[41] This information is sent to a satellite where scientists from anywhere in the world can collect the data. This is how we are currently learning so much about leopard seals diet and foraging habits. With this information we are able to calculate and better understand their diving physiology. They are primarily shallow divers but they do dive deeper than 80 meters in search for food.[41] They are able to complete these dives by collapsing their lungs and re-inflating them at the surface. This is possible by increasing surfactant which coats the alveoli in the lungs for re-inflation. They also have a reinforced trachea to prevent collapse at great depth pressures.[42]
Relationships with humans[edit]
Leopard seals are large predators presenting a potential risk to humans. However, attacks on humans are rare. Most human perceptions of leopard seals are shaped by historic encounters between humans and leopard seals that occurred during the early days of Antarctic exploration.[43] Examples of aggressive behaviour, stalking and attacks are rare, but have been documented.[44] A large leopard seal attacked Thomas Orde-Lees (1877–1958), a member of Sir Ernest Shackleton's Imperial Trans-Antarctic Expedition of 1914–1917, when the expedition was camping on the sea ice.[45] The "sea leopard", about 12 ft (3.7 m) long and 1,100 lb (500 kg), chased Orde-Lees on the ice. He was saved only when another member of the expedition, Frank Wild, shot the animal.[46]
In 1985, Canadian-British explorer Gareth Wood was bitten twice on the leg when a leopard seal tried to drag him off the ice and into the sea. His companions managed to save him by repeatedly kicking the animal in the head with the spiked crampons on their boots.[45][44] On 26 September 2021, near the dive site Spaniard Rock at Simon's Town, South Africa, three spear-fisherman encountered a leopard seal while spearing approximately 400 m offshore. The seal attacked them and, while they were swimming back to shore, disarmed them of their flippers and spearguns and kept harassing the men over the course of half an hour, inflicting multiple bite and puncture wounds.[47]
In 2003, biologist Kirsty Brown of the British Antarctic Survey was killed by a leopard seal while conducting research snorkeling in Antarctica. This was the first recorded human fatality attributed to a leopard seal.[45][44] Brown was part of a team of four researchers taking part in an underwater survey at South Cove, near the U.K.'s Rothera Research Station. Brown and another researcher, Richard Burt, were snorkeling in the water. Burt was snorkeling at a distance of 15 metres (nearly 50 feet) from Brown when the team heard a scream and saw Brown disappear deeper into the water. She was quickly rescued by her team, but they were unable to resuscitate her. It was later revealed that the seal had held Brown underwater for around six minutes at a depth of up to 70 meters (230 ft), drowning her. Furthermore, she suffered a total of 45 separate injuries (bites and scratches), most of which were concentrated around her head and neck. As Brown was snorkeling at the time, she may have even seen the seal approaching her.
In a report read at the inquiry into Brown's death, Professor Ian Boyd from the University of St Andrews stated that the seal may have mistaken her for a fur seal, or may have been frightened by her presence and attacked in defence; Professor Boyd claimed that leopard seal attacks on humans were extremely rare, but warned that they may potentially become more common due to increased human presence in Antarctica. The coroner recorded the cause of death as “accidental” and “caused by drowning due to a leopard seal attack”.[48]
Leopard seals have shown a predilection for attacking the black, torpedo-shaped pontoons of rigid inflatable boats, leading researchers to equip their craft with special protective guards to prevent them from being punctured.[44][49] On the other hand, Paul Nicklen, a National Geographic magazinephotographer, captured pictures of a leopard seal bringing live, injured, and then dead penguins to him, possibly in an attempt to teach the photographer how to hunt.[50][51]
Conservation[edit]
From a conservation standpoint, the only known predators of the leopard seals are orcas and sharks. Because of their limited subpolar distribution in the Antarctic, they may be at risk as polar ice caps diminish with global warming. In the wild, leopard seals can live up to 26 years old.[52] Leopard seal hunting is regulated by the Antarctic Treaty and the Convention for the Conservation of Antarctic Seals (CCAS).[30]
Plesiosaur
| Plesiosauria Temporal range: Late Triassic - Late Cretaceous, | |
|---|---|
 | |
| Restored skeleton of Plesiosaurus | |
 | |
| Skeletal mount of Peloneustes | |
| Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: | †Sauropterygia |
| Clade: | †Pistosauria |
| Order: | †Plesiosauria Blainville, 1835 |
| Subgroups | |
| |
The Plesiosauria (/ˌpliːsiəˈsɔːriə, -zi-/;[2][3] Greek: πλησίος, plesios, meaning "near to" and sauros, meaning "lizard") or Plesiosaurs are an order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia.
Plesiosaurs first appeared in the latest Triassic Period, possibly in the Rhaetian stage, about 203 million years ago.[4] They became especially common during the Jurassic Period, thriving until their disappearance due to the Cretaceous–Paleogene extinction event at the end of the Cretaceous Period, about 66 million years ago. They had a worldwide oceanic distribution, and some species at least partly inhabited freshwater environments.[5]
Plesiosaurs were among the first fossil reptiles discovered. In the beginning of the nineteenth century, scientists realised how distinctive their build was and they were named as a separate order in 1835. The first plesiosaurian genus, the eponymous Plesiosaurus, was named in 1821. Since then, more than a hundred valid species have been described. In the early twenty-first century, the number of discoveries has increased, leading to an improved understanding of their anatomy, relationships and way of life.
Plesiosaurs had a broad flat body and a short tail. Their limbs had evolved into four long flippers, which were powered by strong muscles attached to wide bony plates formed by the shoulder girdle and the pelvis. The flippers made a flying movement through the water. Plesiosaurs breathed air, and bore live young; there are indications that they were warm-blooded.
Plesiosaurs showed two main morphological types. Some species, with the "plesiosauromorph" build, had (sometimes extremely) long necks and small heads; these were relatively slow and caught small sea animals. Other species, some of them reaching a length of up to seventeen metres, had the "pliosauromorph" build with a short neck and a large head; these were apex predators, fast hunters of large prey. The two types are related to the traditional strict division of the Plesiosauria into two suborders, the long-necked Plesiosauroidea and the short-neck Pliosauroidea. Modern research, however, indicates that several "long-necked" groups might have had some short-necked members or vice versa. Therefore, the purely descriptive terms "plesiosauromorph" and "pliosauromorph" have been introduced, which do not imply a direct relationship. "Plesiosauroidea" and "Pliosauroidea" today have a more limited meaning. The term "plesiosaur" is properly used to refer to the Plesiosauria as a whole, but informally it is sometimes meant to indicate only the long-necked forms, the old Plesiosauroidea.
History of discovery[edit]
Early finds[edit]
Skeletal elements of plesiosaurs are among the first fossils of extinct reptiles recognised as such.[6] In 1605, Richard Verstegen of Antwerp illustrated in his A Restitution of Decayed Intelligence plesiosaur vertebrae that he referred to fishes and saw as proof that Great Britain was once connected to the European continent.[7] The Welshman Edward Lhuyd in his Lithophylacii Brittannici Ichnographia from 1699 also included depictions of plesiosaur vertebrae that again were considered fish vertebrae or Ichthyospondyli.[8] Other naturalists during the seventeenth century added plesiosaur remains to their collections, such as John Woodward; these were only much later understood to be of a plesiosaurian nature and are today partly preserved in the Sedgwick Museum.[6]
In 1719, William Stukeley described a partial skeleton of a plesiosaur, which had been brought to his attention by the great-grandfather of Charles Darwin, Robert Darwin of Elston. The stone plate came from a quarry at Fulbeckin Lincolnshire and had been used, with the fossil at its underside, to reinforce the slope of a watering-hole in Elston in Nottinghamshire. After the strange bones it contained had been discovered, it was displayed in the local vicarage as the remains of a sinner drowned in the Great Flood. Stukely affirmed its "diluvial" nature but understood it represented some sea creature, perhaps a crocodile or dolphin.[9] The specimen is today preserved in the Natural History Museum, its inventory number being BMNH R.1330. It is the earliest discovered more or less complete fossil reptile skeleton in a museum collection. It can perhaps be referred to Plesiosaurus dolichodeirus.[6]
During the eighteenth century, the number of English plesiosaur discoveries rapidly increased, although these were all of a more or less fragmentary nature. Important collectors were the reverends William Mounsey and Baptist Noel Turner, active in the Vale of Belvoir, whose collections were in 1795 described by John Nicholls in the first part of his The History and Antiquities of the County of Leicestershire.[10] One of Turner's partial plesiosaur skeletons is still preserved as specimen BMNH R.45 in the British Museum of Natural History; this is today referred to Thalassiodracon.[6]
Naming of Plesiosaurus[edit]
In the early nineteenth century, plesiosaurs were still poorly known and their special build was not understood. No systematic distinction was made with ichthyosaurs, so the fossils of one group were sometimes combined with those of the other to obtain a more complete specimen. In 1821, a partial skeleton discovered in the collection of Colonel Thomas James Birch,[11] was described by William Conybeare and Henry Thomas De la Beche, and recognised as representing a distinctive group. A new genus was named, Plesiosaurus. The generic name was derived from the Greek πλήσιος, plèsios, "closer to" and the Latinised saurus, in the meaning of "saurian", to express that Plesiosaurus was in the Chain of Being more closely positioned to the Sauria, particularly the crocodile, than Ichthyosaurus, which had the form of a more lowly fish.[12]The name should thus be rather read as "approaching the Sauria" or "near reptile" than as "near lizard".[13] Parts of the specimen are still present in the Oxford University Museum of Natural History.[6]
Soon afterwards, the morphology became much better known. In 1823, Thomas Clark reported an almost complete skull, probably belonging to Thalassiodracon, which is now preserved by the British Geological Surveyas specimen BGS GSM 26035.[6] The same year, commercial fossil collector Mary Anning and her family uncovered an almost complete skeleton at Lyme Regis in Dorset, England, on what is today called the Jurassic Coast. It was acquired by the Duke of Buckingham, who made it available to the geologist William Buckland. He in turn let it be described by Conybeare on 24 February 1824 in a lecture to the Geological Society of London,[14]during the same meeting in which for the first time a dinosaur was named, Megalosaurus. The two finds revealed the unique and bizarre build of the animals, in 1832 by Professor Buckland likened to "a sea serpent run through a turtle". In 1824, Conybeare also provided a specific name to Plesiosaurus: dolichodeirus, meaning "longneck". In 1848, the skeleton was bought by the British Museum of Natural History and catalogued as specimen BMNH 22656.[6] When the lecture was published, Conybeare also named a second species: Plesiosaurus giganteus. This was a short-necked form later assigned to the Pliosauroidea.[15]
Plesiosaurs became better known to the general public through two lavishly illustrated publications by the collector Thomas Hawkins: Memoirs of Ichthyosauri and Plesiosauri of 1834[16] and The Book of the Great Sea-Dragons of 1840. Hawkins entertained a very idiosyncratic view of the animals,[17] seeing them as monstrous creations of the devil, during a pre-Adamitic phase of history.[18] Hawkins eventually sold his valuable and attractively restored specimens to the British Museum of Natural History.[19]
During the first half of the nineteenth century, the number of plesiosaur finds steadily increased, especially through discoveries in the sea cliffs of Lyme Regis. Sir Richard Owen alone named nearly a hundred new species. The majority of their descriptions were, however, based on isolated bones, without sufficient diagnosis to be able to distinguish them from the other species that had previously been described. Many of the new species described at this time have subsequently been invalidated. The genus Plesiosaurus is particularly problematic, as the majority of the new species were placed in it so that it became a wastebasket taxon. Gradually, other genera were named. Hawkins had already created new genera, though these are no longer seen as valid. In 1841, Owen named Pliosaurus brachydeirus. Its etymologyreferred to the earlier Plesiosaurus dolichodeirus as it is derived from πλεῖος, pleios, "more fully", reflecting that according to Owen it was closer to the Sauria than Plesiosaurus. Its specific name means "with a short neck".[20] Later, the Pliosauridae were recognised as having a morphology fundamentally different from the plesiosaurids. The family Plesiosauridae had already been coined by John Edward Gray in 1825.[21] In 1835, Henri Marie Ducrotay de Blainville named the order Plesiosauria itself.[22]
American discoveries[edit]
In the second half of the nineteenth century, important finds were made outside of England. While this included some German discoveries, it mainly involved plesiosaurs found in the sediments of the American Cretaceous Western Interior Seaway, the Niobrara Chalk. One fossil in particular marked the start of the Bone Wars between the rival paleontologists Edward Drinker Cope and Othniel Charles Marsh.
In 1867, physician Theophilus Turner near Fort Wallace in Kansas uncovered a plesiosaur skeleton, which he donated to Cope.[23] Cope attempted to reconstruct the animal on the assumption that the longer extremity of the vertebral column was the tail, the shorter one the neck. He soon noticed that the skeleton taking shape under his hands had some very special qualities: the neck vertebrae had chevrons and with the tail vertebrae the joint surfaces were orientated back to front.[24] Excited, Cope concluded to have discovered an entirely new group of reptiles: the Streptosauria or "Turned Saurians", which would be distinguished by reversed vertebrae and a lack of hindlimbs, the tail providing the main propulsion.[25] After having published a description of this animal,[26] followed by an illustration in a textbook about reptiles and amphibians,[27] Cope invited Marsh and Joseph Leidy to admire his new Elasmosaurus platyurus. Having listened to Cope's interpretation for a while, Marsh suggested that a simpler explanation of the strange build would be that Cope had reversed the vertebral column relative to the body as a whole. When Cope reacted indignantly to this suggestion, Leidy silently took the skull and placed it against the presumed last tail vertebra, to which it fitted perfectly: it was in fact the first neck vertebra, with still a piece of the rear skull attached to it.[28] Mortified, Cope tried to destroy the entire edition of the textbook and, when this failed, immediately published an improved edition with a correct illustration but an identical date of publication.[29] He excused his mistake by claiming that he had been misled by Leidy himself, who, describing a specimen of Cimoliasaurus, had also reversed the vertebral column.[30] Marsh later claimed that the affair was the cause of his rivalry with Cope: "he has since been my bitter enemy". Both Cope and Marsh in their rivalry named many plesiosaur genera and species, most of which are today considered invalid.[31]
Around the turn of the century, most plesiosaur research was done by a former student of Marsh, Professor Samuel Wendell Williston. In 1914, Williston published his Water reptiles of the past and present.[32] Despite treating sea reptiles in general, it would for many years remain the most extensive general text on plesiosaurs.[33] In 2013, a first modern textbook was being prepared by Olivier Rieppel. During the middle of the twentieth century, the USA remained an important centre of research, mainly through the discoveries of Samuel Paul Welles.
Recent discoveries[edit]
Whereas during the nineteenth and most of the twentieth century, new plesiosaurs were described at a rate of three or four novel genera each decade, the pace suddenly picked up in the 1990s, with seventeen plesiosaurs being discovered in this period. The tempo of discovery accelerated in the early twenty-first century, with about three or four plesiosaurs being named each year.[34] This implies that about half of the known plesiosaurs are relatively new to science, a result of a far more intense field research. Some of this is taking place away from the traditional areas, e.g. in new sites developed in New Zealand, Argentina, Chile,[35] Norway, Japan, China and Morocco, but the locations of the more original discoveries have proven to be still productive, with important new finds in England and Germany. Some of the new genera are a renaming of already known species, which were deemed sufficiently different to warrant a separate genus name.
In 2002, the "Monster of Aramberri" was announced to the press. Discovered in 1982 at the village of Aramberri, in the northern Mexican state of Nuevo León, it was originally classified as a dinosaur. The specimen is actually a very large plesiosaur, possibly reaching 15 m (49 ft) in length. The media published exaggerated reports claiming it was 25 metres (82 ft) long, and weighed up to 150,000 kilograms (330,000 lb), which would have made it among the largest predators of all time.[36][37]
In 2004, what appeared to be a completely intact juvenile plesiosaur was discovered, by a local fisherman, at Bridgwater Bay National Nature Reserve in Somerset, UK. The fossil, dating from 180 million years ago as indicated by the ammonites associated with it, measured 1.5 metres (4 ft 11 in) in length, and may be related to Rhomaleosaurus. It is probably the best preserved specimen of a plesiosaur yet discovered.[38][39][40]
In 2005, the remains of three plesiosaurs (Dolichorhynchops herschelensis) discovered in the 1990s near Herschel, Saskatchewan were found to be a new species, by Dr. Tamaki Sato, a Japanese vertebrate paleontologist.[41]
In 2006, a combined team of American and Argentinian investigators (the latter from the Argentinian Antarctic Institute and the La Plata Museum) found the skeleton of a juvenile plesiosaur measuring 1.5 metres (4 ft 11 in) in length on Vega Island in Antarctica.[42] The fossil is currently on display at the geological museum of South Dakota School of Mines and Technology.[43]
In 2008, fossil remains of an undescribed plesiosaur that was named Predator X, now known as Pliosaurus funkei, were unearthed in Svalbard.[44] It had a length of 12 m (39 ft), and its bite force of 149 kilonewtons (33,000 lbf) is one of the most powerful known.[45]
In December 2017, a large skeleton of a plesiosaur was found in the continent of Antarctica, the oldest creature on the continent, and the first of its species in Antarctica.[46]
Not only has the number of field discoveries increased, but also, since the 1950s, plesiosaurs have been the subject of more extensive theoretical work. The methodology of cladistics has, for the first time, allowed the exact calculation of their evolutionary relationships. Several hypotheses have been published about the way they hunted and swam, incorporating general modern insights about biomechanics and ecology. The many recent discoveries have tested these hypotheses and given rise to new ones.[original research?]
Evolution[edit]
The Plesiosauria have their origins within the Sauropterygia, a group of perhaps archelosaurian reptiles that returned to the sea. An advanced sauropterygian subgroup, the carnivorous Eusauropterygia with small heads and long necks, split into two branches during the Upper Triassic. One of these, the Nothosauroidea, kept functional elbow and knee joints; but the other, the Pistosauria, became more fully adapted to a sea-dwelling lifestyle. Their vertebral column became stiffer and the main propulsion while swimming no longer came from the tail but from the limbs, which changed into flippers.[47] The Pistosauria became warm-blooded and viviparous, giving birth to live young.[48] Early, basal, members of the group, traditionally called "pistosaurids", were still largely coastal animals. Their shoulder girdles remained weak, their pelves could not support the power of a strong swimming stroke, and their flippers were blunt. Later, a more advanced pistosaurian group split off: the Plesiosauria. These had reinforced shoulder girdles, flatter pelves, and more pointed flippers. Other adaptations allowing them to colonise the open seas included stiff limb joints; an increase in the number of phalanges of the hand and foot; a tighter lateral connection of the finger and toe phalanx series, and a shortened tail.[49][50]
From the earliest Jurassic, the Hettangian stage, a rich radiation of plesiosaurs is known, implying that the group must already have diversified in the Late Triassic; of this diversification, however, only a few very basal forms have been discovered. The subsequent evolution of the plesiosaurs is very contentious. The various cladistic analyses have not resulted in a consensus about the relationships between the main plesiosaurian subgroups. Traditionally, plesiosaurs have been divided into the long-necked Plesiosauroidea and the short-necked Pliosauroidea. However, modern research suggests that some generally long-necked groups might have had short-necked members. To avoid confusion between the phylogeny, the evolutionary relationships, and the morphology, the way the animal is built, long-necked forms are therefore called "plesiosauromorph" and short-necked forms are called "pliosauromorph", without the "plesiosauromorph" species necessarily being more closely related to each other than to the "pliosauromorph" forms.[51]
The latest common ancestor of the Plesiosauria was probably a rather small short-necked form. During the earliest Jurassic, the subgroup with the most species was the Rhomaleosauridae, a possibly very basal split-off of species which were also short-necked. Plesiosaurs in this period were at most five metres (sixteen feet) long. By the Toarcian, about 180 million years ago, other groups, among them the Plesiosauridae, became more numerous and some species developed longer necks, resulting in total body lengths of up to ten metres (33 feet).[52]
In the middle of the Jurassic, very large Pliosauridae evolved. These were characterized by a large head and a short neck, such as Liopleurodon and Simolestes. These forms had skulls up to three metres (ten feet) long and reached a length of up to seventeen metres (56 feet) and a weight of ten tonnes. The pliosaurids had large, conical teeth and were the dominant marine carnivores of their time. During the same time, approximately 160 million years ago, the Cryptoclididae were present, shorter species with a long neck and a small head.[53]
The Leptocleididae radiated during the Early Cretaceous. These were rather small forms that, despite their short necks, might have been more closely related to the Plesiosauridae than to the Pliosauridae. Later in the Early Cretaceous, the Elasmosauridae appeared; these were among the longest plesiosaurs, reaching up to fifteen metres (fifty feet) in length due to very long necks containing as many as 76 vertebrae, more than any other known vertebrate. Pliosauridae were still present as is shown by large predators, such as Kronosaurus.[53]
At the beginning of the Late Cretaceous, the Ichthyosauria became extinct; perhaps a plesiosaur group evolved to fill their niches: the Polycotylidae, which had short necks and peculiarly elongated heads with narrow snouts. During the Late Cretaceous, the elasmosaurids still had many species.[53]
All plesiosaurs became extinct as a result of the K-T event at the end of the Cretaceous period, approximately 66 million years ago.[54]
Relationships[edit]
In modern phylogeny, clades are defined groups that contain all species belonging to a certain branch of the evolutionary tree. One way to define a clade is to let it consist of the last common ancestor of two such species and all its descendants. Such a clade is called a "node clade". In 2008, Patrick Druckenmiller and Anthony Russell in this way defined Plesiosauria as the group consisting of the last common ancestor of Plesiosaurus dolichocheirusand Peloneustes philarchus and all its descendants.[55] Plesiosaurus and Peloneustes represented the main subgroups of the Plesiosauroidea and the Pliosauroidea and were chosen for historical reasons; any other species from these groups would have sufficed.
Another way to define a clade is to let it consist of all species more closely related to a certain species that one in any case wishes to include in the clade than to another species that one to the contrary desires to exclude. Such a clade is called a "stem clade". Such a definition has the advantage that it is easier to include all species with a certain morphology. Plesiosauria was in 2010 by Hillary Ketchum and Roger Benson defined as such a stem-based taxon: "all taxa more closely related to Plesiosaurus dolichodeirus and Pliosaurus brachydeirus than to Augustasaurus hagdorni". Ketchum and Benson (2010) also coined a new clade Neoplesiosauria, a node-based taxon that was defined by as "Plesiosaurus dolichodeirus, Pliosaurus brachydeirus, their most recent common ancestor and all of its descendants".[53] The clade Neoplesiosauria very likely is materially identical to Plesiosauria sensuDruckenmiller & Russell, thus would designate exactly the same species, and the term was meant to be a replacement of this concept.
Benson et al. (2012) found the traditional Pliosauroidea to be paraphyletic in relation to Plesiosauroidea. Rhomaleosauridae was found to be outside Neoplesiosauria, but still within Plesiosauria. The early Carnian pistosaur Bobosaurus was found to be one step more advanced than Augustasaurus in relation to the Plesiosauria and therefore it represented by definition the basalmost known plesiosaur. This analysis focused on basal plesiosaurs and therefore only one derived pliosaurid and one cryptoclidian were included, while elasmosaurids were not included at all. A more detailed analysis published by both Benson and Druckenmiller in 2014 was not able to resolve the relationships among the lineages at the base of Plesiosauria.[56]
The following cladogram follows an analysis by Benson & Druckenmiller (2014).[56]
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Description[edit]
Size[edit]
In general, plesiosaurians varied in adult length from between 1.5 metres (4.9 ft) to about 15 metres (49 ft). The group thus contained some of the largest marine apex predators in the fossil record, roughly equalling the longest ichthyosaurs, mosasaurids, sharks and toothed whales in size. Some plesiosaurian remains, such as a 2.875 metres (9.43 ft) long set of highly reconstructed and fragmentary lower jaws preserved in the Oxford University Museum and referable to Pliosaurus rossicus (previously referred to Stretosaurus[57] and Liopleurodon), indicated a length of 17 metres (56 ft). However, it was recently argued that its size cannot be currently determined due to their being poorly reconstructed and a length of 12.7 metres (42 ft) metres is more likely.[58] MCZ 1285, a specimen currently referable to Kronosaurus queenslandicus, from the Early Cretaceous of Australia, was estimated to have a skull length of 2.21–2.85 m (7.3–9.4 ft).[58][59]
Skeleton[edit]
The typical plesiosaur had a broad, flat, body and a short tail. Plesiosaurs retained their ancestral two pairs of limbs, which had evolved into large flippers.[60] Plesiosaurs were related to the earlier Nothosauridae,[61] that had a more crocodile-like body. The flipper arrangement is unusual for aquatic animals in that probably all four limbs were used to propel the animal through the water by up-and-down movements. The tail was most likely only used for helping in directional control. This contrasts to the ichthyosaurs and the later mosasaurs, in which the tail provided the main propulsion.[62]
To power the flippers, the shoulder girdle and the pelvis had been greatly modified, developing into broad bone plates at the underside of the body, which served as an attachment surface for large muscle groups, able to pull the limbs downwards. In the shoulder, the coracoid had become the largest element covering the major part of the breast. The scapula was much smaller, forming the outer front edge of the trunk. To the middle, it continued into a clavicleand finally a small interclavicular bone. As with most tetrapods, the shoulder joint was formed by the scapula and coracoid. In the pelvis, the bone plate was formed by the ischium at the rear and the larger pubic bone in front of it. The ilium, which in land vertebrates bears the weight of the hindlimb, had become a small element at the rear, no longer attached to either the pubic bone or the thighbone. The hip joint was formed by the ischium and the pubic bone. The pectoral and pelvic plates were connected by a plastron, a bone cage formed by the paired belly ribs that each had a middle and an outer section. This arrangement immobilised the entire trunk.[62]
To become flippers, the limbs had changed considerably. The limbs were very large, each about as long as the trunk. The forelimbs and hindlimbs strongly resembled each other. The humerus in the upper arm, and the femur in the upper leg, had become large flat bones, expanded at their outer ends. The elbow joints and the knee joints were no longer functional: the lower arm and the lower leg could not flex in relation to the upper limb elements, but formed a flat continuation of them. All outer bones had become flat supporting elements of the flippers, tightly connected to each other and hardly able to rotate, flex, extend or spread. This was true of the ulna, radius, metacarpals and fingers, as well of the tibia, fibula, metatarsals and toes. Furthermore, in order to elongate the flippers, the number of phalanges had increased, up to eighteen in a row, a phenomenon called hyperphalangy. The flippers were not perfectly flat, but had a lightly convexly curved top profile, like an airfoil, to be able to "fly" through the water.[62]
While plesiosaurs varied little in the build of the trunk, and can be called "conservative" in this respect, there were major differences between the subgroups as regards the form of the neck and the skull. Plesiosaurs can be divided into two major morphological types that differ in head and neck size. "Plesiosauromorphs", such as Cryptoclididae, Elasmosauridae, and Plesiosauridae, had long necks and small heads. "Pliosauromorphs", such as the Pliosauridae and the Rhomaleosauridae, had shorter necks with a large, elongated head. The neck length variations were not caused by an elongation of the individual cervical vertebrae, but an increase in their number. Elasmosaurus has seventy-two neck vertebrae; the known record is held by the elasmosaurid Albertonectes, with seventy-six cervicals.[63] The large number of joints suggested to early researchers that the neck must have been very flexible; indeed, a swan-like curvature of the neck was assumed to be possible - in Icelandic, plesiosaurs are even called Svaneðlur, "swan lizards". However, modern research has confirmed an earlier conjecture of Williston that the long plate-like spines on top of the vertebrae, the processus spinosi, strongly limited vertical neck movement. Although horizontal curving was less restricted, in general, the neck must have been rather stiff and certainly was incapable of being bent into serpentine coils. This is even more true of the short-necked "pliosauromophs", which had as few as eleven cervical vertebrae. With early forms, the amphicoelous or amphiplat neck vertebrae bore double-headed neck ribs; later forms had single-headed ribs. In the remainder of the vertebral column, the number of dorsal vertebrae varied between about nineteen and thirty-two; of the sacral vertebrae, between two and six, and of the tail vertebrae, between about twenty-one and thirty-two. These vertebrae still possessed the original processes inherited from the land-dwelling ancestors of the Sauropterygia and had not been reduced to fish-like simple discs, as happened with the vertebrae of ichthyosaurs. The tail vertebrae possessed chevron bones. The dorsal vertebrae of plesiosaurs are easily recognisable by two large foramina subcentralia, paired vascular openings at the underside.[62]
The skull of plesiosaurs showed the "euryapsid" condition, lacking the lower temporal fenestrae, the openings at the lower rear sides. The upper temporal fenestrae formed large openings at the sides of the rear skull roof, the attachment for muscles closing the lower jaws. Generally, the parietal bones were very large, with a midline crest, while the squamosal bones typically formed an arch, excluding the parietals from the occiput. The eye sockets were large, in general pointing obliquely upwards; the pliosaurids had more sideways directed eyes. The eyes were supported by scleral rings, the form of which shows that they were relatively flat, an adaptation to diving. The anteriorly placed internal nostrils, the choanae, have palatal grooves to channel water, the flow of which would be maintained by hydrodynamic pressure over the posteriorly placed, in front of the eye sockets, external nares during swimming. According to one hypothesis, during its passage through the nasal ducts, the water would have been 'smelled' by olfactory epithelia.[64][65] However, more to the rear, a second pair of openings is present in the palate; a later hypothesis holds that these are the real choanae and the front pair in reality represented paired salt glands.[66] The distance between the eye sockets and the nostrils was so limited because the nasal bones were strongly reduced, even absent in many species. The premaxillae directly touched the frontal bones; in the elasmosaurids, they even reached back to the parietal bones. Often, the lacrimal bones were also lacking.[50]
The tooth form and number was very variable. Some forms had hundreds of needle-like teeth. Most species had larger conical teeth with a round or oval cross-section. Such teeth numbered four to six in the premaxilla and about fourteen to twenty-five in the maxilla; the number in the lower jaws roughly equalled that of the skull. The teeth were placed in tooth-sockets, had vertically wrinkled enamel and lacked a true cutting edge or carina. With some species, the front teeth were notably longer, to grab prey.[67]
Soft tissues[edit]
Soft tissue remains of plesiosaurs are rare, but sometimes, especially in shale deposits, they have been partly preserved, e.g. showing the outlines of the body. An early discovery in this respect was the holotype of Plesiosaurus conybeari (presently Attenborosaurus). From such finds it is known that the skin was smooth, without apparent scales but with small wrinkles, that the trailing edge of the flippers extended considerably behind the limb bones;[68] and that the tail bore a vertical fin, as reported by Wilhelm Dames in his description of Plesiosaurus guilelmiimperatoris (presently Seeleyosaurus).[69] The possibility of a tail fluke has been confirmed by recent studies on the caudal neural spine form of Pantosaurus, Cryptoclidus and Rhomaleosaurus zetlandicus.[70][71][72] A 2020 study claims that the caudal fin was horizontal in configuration.[73]
Paleobiology[edit]
Food[edit]
The probable food source of plesiosaurs varied depending on whether they belonged to the long-necked "plesiosauromorph" forms or the short-necked "pliosauromorph" species.
The extremely long necks of "plesiosauromorphs" have caused speculation as to their function from the very moment their special build became apparent. Conybeare had offered three possible explanations. The neck could have served to intercept fast-moving fish in a pursuit. Alternatively, plesiosaurs could have rested on the sea bottom, while the head was sent out to search for prey, which seemed to be confirmed by the fact the eyes were directed relatively upwards. Finally, Conybeare suggested the possibility that plesiosaurs swam on the surface, letting their necks plunge downwards to seek food at lower levels. All these interpretations assumed that the neck was very flexible. The modern insight that the neck was, in fact, rather rigid, with limited vertical movement, has necessitated new explanations. One hypothesis is that the length of the neck made it possible to surprise schools of fish, the head arriving before the sight or pressure wave of the trunk could alert them. "Plesiosauromorphs" hunted visually, as shown by their large eyes, and perhaps employed a directional sense of olfaction. Hard and soft-bodied cephalopods probably formed part of their diet. Their jaws were probably strong enough to bite through the hard shells of this prey type. Fossil specimens have been found with cephalopod shells still in their stomach.[74] The bony fish (Osteichthyes), which further diversified during the Jurassic, were likely prey as well. A very different hypothesis claims that "plesiosauromorphs" were bottom feeders. The stiff necks would have been used to plough the sea bottom, eating the benthos. This would have been proven by long furrows present in ancients seabeds.[75][76] Such a lifestyle has in 2017 been suggested for Morturneria.[77]"Plesiosauromorphs" were not well adapted to catching large fast-moving prey, as their long necks, though seemingly streamlined, caused enormous skin friction. Sankar Chatterjee suggested in 1989 that some Cryptocleididae were suspension feeders, filtering plankton. Aristonectes e.g. had hundreds of teeth, allowing it to sieve small Crustacea from the water.[78]
The short-necked "pliosauromorphs" were top carnivores, or apex predators, in their respective foodwebs.[79] They were pursuit predators[80] or ambush predators of various sized prey and opportunistic feeders; their teeth could be used to pierce soft-bodied prey, especially fish.[81] Their heads and teeth were very large, suited to grab and rip apart large animals. Their morphology allowed for a high swimming speed. They too hunted visually.
Plesiosaurs were themselves prey for other carnivores, as shown by bite marks left by a shark that have been discovered on a fossilized plesiosaur fin[82]and the fossilized remains of a mosasaur's stomach contents that are thought to be the remains of a plesiosaur.[83]
Skeletons have also been discovered with gastroliths, stones, in their stomachs, though whether to help break down food, especially cephalopods, in a muscular gizzard, or to vary buoyancy, or both, has not been established.[84][85] However, the total weight of the gastroliths found in various specimens appears to be insufficient to modify the buoyancy of these large reptiles.[86] The first plesiosaur gastroliths, found with Mauisaurus gardneri (a nomen nudum[87]), were reported by Harry Govier Seeley in 1877.[88] The number of these stones per individual is often very large. In 1949, a fossil of Alzadasaurus (specimen SDSM 451, later renamed to Styxosaurus) showed 253 of them.[89] The size of individual stones is often considerable. In 1991 an elasmosaurid specimen, KUVP 129744, was investigated, containing a gastrolith with a diameter of seventeen centimetres and a weight of 1300 grams; and a somewhat shorter stone of 1490 grams. In total, forty-seven gastroliths were present, with a combined weight of 13 kilograms. The size of the stones has been seen as an indication that they were not swallowed by accident, but deliberately, the animal perhaps covering large distances in search of a suitable rock type.[90] The type specimen of Dolichorhynchops tropicensis (MNA V10046) is associated with 289 gastroliths, which is unusual in comparison to most polycotylid skeletons that generally lack gastroliths. Ranging from less than 0.1 grams to 18.5 grams, the total mass of the gastroliths was about 518 grams. About three-quarters of the stones weighed less than 2 grams, with the mean mass and median mass of the stones respectively estimated at 1.9 grams and 0.8 grams. The gastroliths had high mean value and variability in sphericity, suggesting that this individual was obtaining its stones from rivers located along the western side of the Western Interior Seaway.[91]
Locomotion[edit]
Flipper movement[edit]
The distinctive four-flippered body-shape has caused considerable speculation about what kind of stroke plesiosaurs used. The only modern group with four flippers are the sea turtles, which only use the front pair for propulsion. Conybeare and Buckland had already compared the flippers with bird wings. However, such a comparison was not very informative, as the mechanics of bird flight in this period were poorly understood. By the middle of the nineteenth century, it was typically assumed that plesiosaurs employed a rowing movement. The flippers would have been moved forward in a horizontal position, to minimise friction, and then axially rotated to a vertical position in order to be pulled to the rear, causing the largest possible reactive force. In fact, such a method would be very inefficient: the recovery stroke in this case generates no thrust and the rear stroke generates an enormous turbulence. In the early twentieth century, the newly discovered principles of bird flight suggested to several researchers that plesiosaurs, like turtles and penguins, made a flying movement while swimming. This was e.g. proposed by Eberhard Fraas in 1905,[92] and in 1908 by Othenio Abel.[93] When flying, the flipper movement is more vertical, its point describing an oval or "8". Ideally, the flipper is first moved obliquely to the front and downwards and then, after a slight retraction and rotation, crosses this path from below to be pulled to the front and upwards. During both strokes, down and up, according to Bernoulli's principle, forward and upward thrust is generated by the convexly curved upper profile of the flipper, the front edge slightly inclined relative to the water flow, while turbulence is minimal. However, despite the evident advantages of such a swimming method, in 1924 the first systematic study on the musculature of plesiosaurs by David Meredith Seares Watson concluded they nevertheless performed a rowing movement.[94]
During the middle of the twentieth century, Watson's "rowing model" remained the dominant hypothesis regarding the plesiosaur swimming stroke. In 1957, Lambert Beverly Halstead, at the time using the family name Tarlo, proposed a variant: the hindlimbs would have rowed in the horizontal plane but the forelimbs would have paddled, moved to below and to the rear.[95][96] In 1975, the traditional model was challenged by Jane Ann Robinson, who revived the "flying" hypothesis. She argued that the main muscle groups were optimally placed for a vertical flipper movement, not for pulling the limbs horizontally, and that the form of the shoulder and hip joints would have precluded the vertical rotation needed for rowing.[97] In a subsequent article, Robinson proposed that the kinetic energy generated by the forces exerted on the trunk by the strokes, would have been stored and released as elastic energy in the ribcage, allowing for an especially efficient and dynamic propulsion system.[98]
In Robinson's model, both the downstroke and the upstroke would have been powerful. In 1982, she was criticised by Samuel Tarsitano, Eberhard Freyand Jürgen Riess, who claimed that, while the muscles at the underside of the shoulder and pelvic plates were clearly powerful enough to pull the limbs downwards, comparable muscle groups on the top of these plates to elevate the limbs were simply lacking, and, had they been present, could not have been forcefully employed, their bulging carrying the danger of hurting the internal organs. They proposed a more limited flying model in which a powerful downstroke was combined with a largely unpowered recovery, the flipper returning to its original position by the momentum of the forward moving and temporarily sinking body.[99][100] This modified flying model became a popular interpretation. Less attention was given to an alternative hypothesis by Stephen Godfrey in 1984, which proposed that both the forelimbs and hindlimbs performed a deep paddling motion to the rear combined with a powered recovery stroke to the front, resembling the movement made by the forelimbs of sea-lions.[101]
In 2010, Frank Sanders and Kenneth Carpenter published a study concluding that Robinson's model had been correct. Frey & Riess would have been mistaken in their assertion that the shoulder and pelvic plates had no muscles attached to their upper sides. While these muscle groups were probably not very powerful, this could easily have been compensated by the large muscles on the back, especially the latissimus dorsi, which would have been well developed in view of the high spines on the backbone. Furthermore, the flat build of the shoulder and hip joints strongly indicated that the main movement was vertical, not horizontal.[102]
Gait[edit]
Like all tetrapods with limbs, plesiosaurs must have had a certain gait, a coordinated movement pattern of the, in this case, flippers. Of all the possibilities, in practice attention has been largely directed to the question of whether the front pair and hind pair moved simultaneously, so that all four flippers were engaged at the same moment, or in an alternate pattern, each pair being employed in turn. Frey & Riess in 1991 proposed an alternate model, which would have had the advantage of a more continuous propulsion.[103] In 2000, Theagarten Lingham-Soliar evaded the question by concluding that, like sea turtles, plesiosaurs only used the front pair for a powered stroke. The hind pair would have been merely used for steering. Lingham-Soliar deduced this from the form of the hip joint, which would have allowed for only a limited vertical movement. Furthermore, a separation of the propulsion and steering function would have facilitated the general coordination of the body and prevented a too extreme pitch. He rejected Robinson's hypothesis that elastic energy was stored in the ribcage, considering the ribs too stiff for this.[104]
The interpretation by Frey & Riess became the dominant one, but was challenged in 2004 by Sanders, who showed experimentally that, whereas an alternate movement might have caused excessive pitching, a simultaneous movement would have caused only a slight pitch, which could have been easily controlled by the hind flippers. Of the other axial movements, rolling could have been controlled by alternately engaging the flippers of the right or left side, and yaw by the long neck or a vertical tail fin. Sanders did not believe that the hind pair was not used for propulsion, concluding that the limitations imposed by the hip joint were very relative.[105] In 2010, Sanders & Carpenter concluded that, with an alternating gait, the turbulence caused by the front pair would have hindered an effective action of the hind pair. Besides, a long gliding phase after a simultaneous engagement would have been very energy efficient.[102] It is also possible that the gait was optional and was adapted to the circumstances. During a fast steady pursuit, an alternate movement would have been useful; in an ambush, a simultaneous stroke would have made a peak speed possible. When searching for prey over a longer distance, a combination of a simultaneous movement with gliding would have cost the least energy.[106] In 2017, a study by Luke Muscutt, using a robot model, concluded that the rear flippers were actively employed, allowing for a 60% increase of the propulsive force and a 40% increase of efficiency. The stroke would have been at its most powerful using a slightly alternating gait, the rear flippers engaging just after the front flippers, to benefit from their wake. However, there would not have been a single optimal phase for all conditions, the gait likely having been changed as the situation demanded.[107]
Speed[edit]
In general, it is hard to determine the maximum speed of extinct sea creatures. For plesiosaurs, this is made more difficult by the lack of consensus about their flipper stroke and gait. There are no exact calculations of their Reynolds Number. Fossil impressions show that the skin was relatively smooth, not scaled, and this may have reduced form drag.[102] Small wrinkles are present in the skin that may have prevented separation of the laminar flow in the boundary layer and thereby reduced skin friction.
Sustained speed may be estimated by calculating the drag of a simplified model of the body, that can be approached by a prolate spheroid, and the sustainable level of energy output by the muscles. A first study of this problem was published by Judy Massare in 1988.[108] Even when assuming a low hydrodynamic efficiency of 0.65, Massare's model seemed to indicate that plesiosaurs, if warm-blooded, would have cruised at a speed of four metres per second, or about fourteen kilometres per hour, considerably exceeding the known speeds of extant dolphins and whales.[109] However, in 2002 Ryosuke Motani showed that the formulae that Massare had used, had been flawed. A recalculation, using corrected formulae, resulted in a speed of half a metre per second (1.8 km/h) for a cold-blooded plesiosaur and one and a half metres per second (5.4 km/h) for an endothermic plesiosaur. Even the highest estimate is about a third lower than the speed of extant Cetacea.[110]
Massare also tried to compare the speeds of plesiosaurs with those of the two other main sea reptile groups, the Ichthyosauria and the Mosasauridae. She concluded that plesiosaurs were about twenty percent slower than advanced ichthyosaurs, which employed a very effective tunniform movement, oscillating just the tail, but five percent faster than mosasaurids, which were assumed to swim with an inefficient anguilliform, eel-like, movement of the body.[109]
The many plesiosaur species may have differed considerably in their swimming speeds, reflecting the various body shapes present in the group. While the short-necked "pliosauromorphs" (e.g. Liopleurodon) may have been fast swimmers, the long-necked "plesiosauromorphs" were built more for manoeuvrability than for speed, slowed by a strong skin friction, yet capable of a fast rolling movement. Some long-necked forms, such as the Elasmosauridae, also have relatively short stubby flippers with a low aspect ratio, further reducing speed but improving roll.[111]
Diving[edit]
Few data are available that show exactly how deep plesiosaurs dived. That they dived to some considerable depth is proven by traces of decompression sickness. The heads of the humeri and femora with many fossils show necrosis of the bone tissue, caused by a too rapid ascent after deep diving. However, this does not allow to deduce some exact depth as the damage could have been caused by a few very deep dives, or alternatively by a great number of relatively shallow descents. The vertebrae show no such damage: they were probably protected by a superior blood supply, made possible by the arteries entering the bone through the two foramina subcentralia, large openings in their undersides.[112]
Descending would have been helped by a negative Archimedes Force, i.e. being denser than water. Of course, this would have had the disadvantage of hampering coming up again. Young plesiosaurs show pachyostosis, an extreme density of the bone tissue, which might have increased relative weight. Adult individuals have more spongy bone. Gastroliths have been suggested as a method to increase weight[113] or even as means to attain neutral buoyancy, swallowing or spitting them out again as needed.[114] They might also have been used to increase stability.[115]
The relatively large eyes of the Cryptocleididae have been seen as an adaptation to deep diving.[116]
Tail role[edit]
A 2020 study has posited that sauropterygians relied on vertical tail strokes much like cetaceans. In plesiosaurs the trunk was rigid so this action was more limited and in conjunction with the flippers.[73]
Metabolism[edit]
Traditionally, it was assumed that extinct reptile groups were cold-blooded like modern reptiles. New research during the past decades has led to the conclusion that some groups, such as theropod dinosaurs and pterosaurs, were very likely warm-blooded. Whether perhaps plesiosaurs were warm-blooded as well is difficult to determine. One of the indications of a high metabolism is the presence of fast-growing fibrolamellar bone. The pachyostosis with juvenile individuals makes it hard to establish whether plesiosaurs possessed such bone, though. However, it has been possible to check its occurrence with more basal members of the more inclusive group that plesiosaurs belonged to, the Sauropterygia. A study in 2010 concluded that fibrolamellar bone was originally present with sauropterygians.[117] A subsequent publication in 2013 found that the Nothosauridae lacked this bone matrix type but that basal Pistosauria possessed it, a sign of a more elevated metabolism.[118] It is thus more parsimonious to assume that the more derived pistosaurians, the plesiosaurs, also had a faster metabolism. A paper published in 2018 claimed that plesiosaurs had resting metabolic rates (RMR) in the range of birds based on quantitative osteohistological modelling.[119] However, these results are problematic in view of general principles of vertebrate physiology (see Kleiber's law); evidence from isotope studies of plesiosaur tooth enamel indeed suggests endothermy at lower RMRs, with inferred body temperatures of ca. 26 °C (79 °F).[120]
Reproduction[edit]
As reptiles in general are oviparous, until the end of the twentieth century it had been seen as possible that smaller plesiosaurs may have crawled up on a beach to lay eggs, like modern turtles. Their strong limbs and a flat underside seemed to have made this feasible. This method was, for example, defended by Halstead. However, as those limbs no longer had functional elbow or knee joints and the underside by its very flatness would have generated a lot of friction, already in the nineteenth century it was hypothesised that plesiosaurs had been viviparous. Besides, it was hard to conceive how the largest species, as big as whales, could have survived a beaching. Fossil finds of ichthyosaur embryos showed that at least one group of marine reptiles had borne live young. The first to claim that similar embryos had been found in plesiosaurs was Harry Govier Seeley, who reported in 1887 having acquired a nodule with four to eight tiny skeletons.[121] In 1896, he described this discovery in more detail.[122] If authentic, the embryos of plesiosaurs would have been very small, like those of ichthyosaurs. However, in 1982 Richard Anthony Thulborn showed that Seeley had been deceived by a "doctored" fossil of a nest of crayfish.[123]
An actual plesiosaur specimen found in 1987 eventually proved that plesiosaurs gave birth to live young:[124] This fossil of a pregnant Polycotyluslatippinus shows that these animals gave birth to a single large juvenile and probably invested parental care in their offspring, similar to modern whales. The young was 1.5 metres (five feet) long and thus large compared to its mother of five metres (sixteen feet) length, indicating a K-strategy in reproduction.[125] Little is known about growth rates or a possible sexual dimorphism.
Social behaviour and intelligence[edit]
From the parental care indicated by the large size of the young, it can be deduced that social behaviour in general was relatively complex.[124] It is not known whether plesiosaurs hunted in packs. Their relative brain size seems to be typical for reptiles. Of the senses, sight and smell were important, hearing less so; elasmosaurids have lost the stapes completely. It has been suggested that with some groups the skull housed electro-sensitive organs.[126][127]
Paleopathology[edit]
Some plesiosaur fossils show pathologies, the result of illness or old age. In 2012, a mandible of Pliosaurus was described with a jaw joint clearly afflicted by arthritis, a typical sign of senescence.[128]
Distribution[edit]
Plesiosaur fossils have been found on every continent, including Antarctica.[129]
Stratigraphic distribution[edit]
The following is a list of geologic formations that have produced plesiosaur fossils.
In contemporary culture[edit]
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The belief that plesiosaurs are dinosaurs is a common misconception, and plesiosaurs are often erroneously depicted as dinosaurs in popular culture.[135][136]
It has been suggested that legends of sea serpents and modern sightings of supposed monsters in lakes or the sea could be explained by the survival of plesiosaurs into modern times. This cryptozoological proposal has been rejected by the scientific community at large, which considers it to be based on fantasy and pseudoscience. Purported plesiosaur carcasses have been shown to be partially decomposed corpses of basking sharksinstead.[137][138][139]
While the Loch Ness monster is often reported as looking like a plesiosaur, it is also often described as looking completely different. A number of reasons have been presented for it to be unlikely to be a plesiosaur. They include the assumption that the water in the loch is too cold for a presumed cold-blooded reptile to be able to survive easily, the assumption that air-breathing animals would be easy to see whenever they appear at the surface to breathe,[140] the fact that the loch is too small and contains insufficient food to be able to support a breeding colony of large animals, and finally the fact that the lake was formed only 10,000 years ago at the end of the last ice age, and the latest fossil appearance of plesiosaurs dates to over 66 million years ago.[141] Frequent explanations for the sightings include waves, floating inanimate objects, tricks of the light, swimming known animals and practical jokes.[142] Nevertheless, in the popular imagination, plesiosaurs have come to be identified with the Monster of Loch Ness. That has had the advantage of making the group better known to the general public, but the disadvantage that people have trouble taking the subject seriously, forcing paleontologists to explain time and time again that plesiosaurs really existed and are not merely creatures of myth or fantasy.[143]
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