Mosasaurus is a genus of mosasaur
Mosasaurs are large extinct marine lizards. The first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764...

, carnivorous, aquatic lizard
Lizards are a widespread group of squamate reptiles, with nearly 3800 species, ranging across all continents except Antarctica as well as most oceanic island chains...

s, somewhat resembling flippered crocodile
A crocodile is any species belonging to the family Crocodylidae . The term can also be used more loosely to include all extant members of the order Crocodilia: i.e...

s, with elongated heavy jaws. The genus existed during the Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...

 age of the Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...

 period (Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...

 era), around 70-65 millions years ago in the area of modern Western Europe and North America. The name means "Meuse lizard", as the first specimen was found near the Meuse River
Meuse River
The Maas or Meuse is a major European river, rising in France and flowing through Belgium and the Netherlands before draining into the North Sea...

 (Latin Mosa + Greek sauros lizard). The genus Capelliniosuchus, once thought to be a metriorhynchid crocodylian, is a junior synonym of Mosasaurus.


As with most mosasaurs, their legs and feet are modified into hydrofoil-like flippers, with the forelimbs larger than the hindlimbs. Like its American relatives Tylosaurus
Tylosaurus was a mosasaur, a large, predatory marine lizard closely related to modern monitor lizards and to snakes.-Paleobiology:...

and Hainosaurus
Hainosaurus is an extinct genus of marine lizard belonging to the mosasaur family. It was one of the largest mosasaurs, though its size has been revised more than once. At first it was estimated to be , and the largest mosasaurid. During the 1990s, its size was revised to long; more recently,...

, Mosasaurus reached lengths of about 15 meters.
However, Mosasaurus was more robust than the similarly sized tylosaurine mosasaurs.

Mosasaurus was among the last mosasaur genera, and among the largest. The skull was more robustly built than other mosasaurs, as the mandible
The mandible pronunciation or inferior maxillary bone forms the lower jaw and holds the lower teeth in place...

s articulated very tightly with the skull. It had a deep, barrel-shaped body, and with its fairly large eyes, poor binocular vision, and poorly developed olfactory bulbs, experts believe that Mosasaurus lived near the ocean surface, where it preyed on fish, turtles, ammonites, and possibly smaller mosasaurs. The animal remained near the surface and although it was able to dive, it evidentially did not venture into deeper waters.

The skull of Mosasaurus tapered off into a short, conical process, and the jaws were armed with massive, sharp, conical teeth. Their paddle-like limbs had five digits in front and four in back. The trunk terminated in a strong tail which, together with serpentine undulation of the whole body, contributed far more to the animal's locomotion than did the limbs.

First discoveries

Mosasaurus was the first genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 of mosasaur
Mosasaurs are large extinct marine lizards. The first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764...

 (and in fact, the first genus of prehistoric reptile
Reptiles are members of a class of air-breathing, ectothermic vertebrates which are characterized by laying shelled eggs , and having skin covered in scales and/or scutes. They are tetrapods, either having four limbs or being descended from four-limbed ancestors...

) to be named. The first remains known to science were a fragmentary skull from a chalk quarry in the St Pietersberg
Mount Saint Peter
Mount Saint Peter is a ridge running north to south between the valleys of the Geer and the Meuse from Maastricht in the Netherlands to the area of Liège in Belgium....

, a hill near Maastricht
Maastricht is situated on both sides of the Meuse river in the south-eastern part of the Netherlands, on the Belgian border and near the German border...

, Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

, found in 1764 and collected by lieutenant Jean Baptiste Drouin in 1766. It was described in 1790 by Martinus van Marum, the first director of the Teylers Museum
Teylers Museum
Teyler's Museum , located in Haarlem, is the oldest museum in the Netherlands. The museum is in the former home of Pieter Teyler van der Hulst . He was a wealthy cloth merchant and Amsterdam banker of Scottish descent, who bequeathed his fortune for the advancement of religion, art and science...

 at Haarlem
Haarlem is a municipality and a city in the Netherlands. It is the capital of the province of North Holland, the northern half of Holland, which at one time was the most powerful of the seven provinces of the Dutch Republic...

, who considered it to be a fish. The same year van Marum procured the fossil for the museum; it is still part of the collection as TM 7424.

At some time between 1770 and 1774 (the often mentioned date of 1780 is incorrect) a second partial skull was discovered and procured by canon
Canon (priest)
A canon is a priest or minister who is a member of certain bodies of the Christian clergy subject to an ecclesiastical rule ....

 Theodorus Joannes Godding, who displayed it in his country house on the slope of the hill. A local retired German/Dutch army physician, Johann Leonard Hoffmann, also collected some fragments and published about the skull; his correspondence with international scientists made the find world famous. Hoffmann presumed the animal was a crocodile. In 1786 however, the Dutch Professor Petrus Camper
Petrus Camper
Peter, Pieter, or usually Petrus Camper was a Dutch physician, anatomist, physiologist, midwife, zoologist, anthropologist, paleontologist and a naturalist. He studied the orangutan, the rhinoceros, the skull of a whale...

 disagreed and concluded the remains were those of an "unknown sperm whale
Sperm Whale
The sperm whale, Physeter macrocephalus, is a marine mammal species, order Cetacea, a toothed whale having the largest brain of any animal. The name comes from the milky-white waxy substance, spermaceti, found in the animal's head. The sperm whale is the only living member of genus Physeter...

", of a "Physeteris incognitis ex Monte S. Petri".

In 1794 Maastricht, an important fortress city, was captured by the French revolutionary armies. Accompanying the French troops was geologist Barthélemy Faujas de Saint-Fond
Barthélemy Faujas de Saint-Fond
Barthélemy Faujas de Saint-Fond , French geologist and traveller, was born at Montélimar. He was educated at the Jesuit's College at Lyon; afterwards he went to Grenoble where he studied law and was admitted as an advocate to the parlement.He rose to be president of the seneschal's court in...

 on a mission to secure the piece, together with représentant du peuple (political commissar
Political commissar
The political commissar is the supervisory political officer responsible for the political education and organisation, and loyalty to the government of the military...

) Freicine who during the campaign tried to transport anything of artistic or scientific value he could lay his hands on to France. Finding that it had been removed from the cottage and hidden within the fortress, Freicine offered "six hundred bottles of good wine" to those troops being the first to locate the skull; soon a dozen grenadiers claimed their reward, carrying the piece with them. Early 1795 it was moved to Paris
Paris is the capital and largest city in France, situated on the river Seine, in northern France, at the heart of the Île-de-France region...

 as war booty, by decree declared a national heritage and added to the collection of the new Muséum national d'Histoire naturelle
Muséum national d'histoire naturelle
The Muséum national d'Histoire naturelle is the National Museum of Natural History in Paris, France.- History :The museum was formally founded on 10 June 1793, during the French Revolution...

In 1799 Faujas de Saint-Fond published his Histoire naturelle de la montagne de Saint-Pierre de Maestricht [Tome 2], which also contained an account of the circumstances of the find. According to him Dr Hoffmann paid the quarrymen extra to look out for especially large specimens. When the skull was found in 1770 Hoffmann would have been present during the excavation. Afterwards Godding would have claimed his rights as landowner and forced Hoffmann to relinquish his ownership through a lawsuit, won by influencing the court. De Saint-Fond nevertheless, in 1795, saved the specimen for science, paying a considerable indemnity to Godding to compensate for his loss. However, as Dutch historian Peggy Rompen showed, of this famous story very little can be substantiated by other sources. Godding was the original owner, Hoffmann clearly never possessed the fossil, there was no lawsuit, de Saint-Fond probably never paid anything and the entire account seems to have been fabricated by him to justify the dispossession by military force.

Identification as an extinct reptile

De Saint-Fond still assumed the specimen represented a crocodile. In 1798 the son of Petrus Camper, Adriaan Gilles Camper, again studied the fossil indirectly by reconsidering the description by his father. He was the first to reach the conclusion that the remains were those of a giant monitor
Monitor lizard
Monitor lizards are usually large reptiles, although some can be as small as in length. They have long necks, powerful tails and claws, and well-developed limbs. Most species are terrestrial, but arboreal and semiaquatic monitors are also known...

, which result in 1799 he corresponded to Georges Cuvier
Georges Cuvier
Georges Chrétien Léopold Dagobert Cuvier or Jean Léopold Nicolas Frédéric Cuvier , known as Georges Cuvier, was a French naturalist and zoologist...


In 1808 Cuvier confirmed Camper's result. The fossil had already become part of Cuvier's first speculations on the possibility of animal species going extinct
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...

. The idea of extinction paved the way for his theory of catastrophism
Catastrophism is the theory that the Earth has been affected in the past by sudden, short-lived, violent events, possibly worldwide in scope. The dominant paradigm of modern geology is uniformitarianism , in which slow incremental changes, such as erosion, create the Earth's appearance...

 or "consecutive creations", one of the predecessors of the evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...

 theory. Prior to this, almost all fossil reptile specimens, when recognized as having come from one-living animals, were interpreted as forms similar to those of the modern day: crocodiles, fish, whales, or large land mammals. Cuvier's idea that the Maastricht specimen was a gigantic version of a modern animal unlike any species alive today seemed strange, even to him. He justified this by trusting his techniques in the then-developing field of comparative anatomy
Comparative anatomy
Comparative anatomy is the study of similarities and differences in the anatomy of organisms. It is closely related to evolutionary biology and phylogeny .-Description:...

, which he had already used to identify giant, extinct members of other modern groups known only from fossils, including giant tapir
A Tapir is a large browsing mammal, similar in shape to a pig, with a short, prehensile snout. Tapirs inhabit jungle and forest regions of South America, Central America, and Southeast Asia. There are four species of Tapirs: the Brazilian Tapir, the Malayan Tapir, Baird's Tapir and the Mountain...

 and ground sloth
Ground sloth
Ground sloths are a diverse group of extinct sloths, in the mammalian superorder Xenarthra. Their most recent survivors lived in the Antilles, where it has been proposed they may have survived until 1550 CE; however, the youngest AMS radiocarbon date reported is 4190 BP, calibrated to c. 4700 BP...


A scientific name had not yet been given to the new species, the specimen usually being referred to as the Grand Animal fossile des Carrières de Maëstricht or "Great Fossil Animal of the Maastricht quarries". In 1822 William Daniel Conybeare
William Daniel Conybeare
William Daniel Conybeare FRS , dean of Llandaff, was an English geologist, palaeontologist and clergyman. He is probably best known for his ground-breaking work on marine reptile fossils in the 1820s, including important papers for the Geological Society of London on ichthyosaur anatomy and the...

 named it Mosasaurus after the Latin name (Mosa) of the Maas (Meuse) River passing along Mount Saint Peter, the second skull being the holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...

, MNHNP AC9648. The specific name (epithet) hoffmannii was added by G.A. Mantell
Gideon Mantell
Gideon Algernon Mantell MRCS FRS was an English obstetrician, geologist and palaeontologist...

 in 1829, honouring Hoffmann, on the presumption he was the discoverer of the type specimen. The emendated form hoffmanni often used today, is contrary to the rules of the ICZN
International Code of Zoological Nomenclature
The International Code of Zoological Nomenclature is a widely accepted convention in zoology that rules the formal scientific naming of organisms treated as animals...

 that state "the original spelling of a name [...] is to be preserved."
In 1854 German biologist Hermann Schlegel
Hermann Schlegel
Hermann Schlegel was a German ornithologist and herpetologist.-Early life and education:Schlegel was born at Altenburg, the son of a brassfounder. His father collected butterflies, which stimulated Schlegel's interest in natural history...

 was the first to conjecture Mosasaurus had flippers instead of normal feet.

In 1998, another, even bigger and more intact fossil skull was found in the Maastricht limestone quarries, nicknamed "Bèr", and displayed in the Maastricht Natural History Museum
Maastricht Natural History Museum
The Maastricht Natural History Museum is a natural history museum in the Dutch city of Maastricht. The museum is located in a former monastery complex called Grauwzusters in the historic district Jekerkwartier.The collection is dedicated to the geology, paleontology, flora and fauna of South...

. However, it was determined this find represented a new species of the genus Prognathodon
Prognathodon is an extinct genus of marine reptile belonging to the mosasaur family. It had protective bony rings surrounding its eye sockets, indicating it lived in deep water. its fossil remains have been found in the U.S.A , Canada , Belgium, New Zealand, Morocco and The Netherlands...


Classification and species

The family Mosasauridae is split into several subfamilies, with Mosasaurus being placed within Mosasaurinae
Mosasaurinae is a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates.Russell defined the Mosasurinae as differing from all other mosasaurs as follows: "Small rostrum present or absent anterior to premaxillary teeth. Fourteen or more teeth present in dentary and maxilla...

. This subfamily, in turn, is further split into smaller tribes
Tribe (biology)
In biology, a tribe is a taxonomic rank between family and genus. It is sometimes subdivided into subtribes.Some examples include the tribes: Canini, Acalypheae, Hominini, Bombini, and Antidesmeae.-See also:* Biological classification* Rank...

, with Mosasaurus being grouped with Clidastes
Clidastes is an extinct genus of mosasaur lizard from marine environments of the Late Cretaceous.Clidastes was an agile and fast swimmer that cruised the surface or shallow waters hunting for fish, flying reptiles and anything that got too close.- Appearance :Clidastes was the smallest of the...

, Moanasaurus
Moanasaurus was a genus of mosasaur from the Late Cretaceous period. Its fossil remains have been discovered in the North Island of New Zealand. Moanasaurus was a very large mosasaurine known originally from a disarticulated skull, vertebrae, ribs and paddle bones...

, Amphekepubis
Amphekepubis is a genus of mosasaur from the Late Cretaceous of Mexico.-References:*-External links:*...

, and Liodon
Liodon is a genus of mosasaur from the Late Cretaceous. Remains assigned to this genus have been found in Africa, Asia, Europe, America and South America, and New Zealand. It was first named by Richard Owen as Leiodon, but that name was already in use for a fish, necessitating the name...

in the tribe Mosasaurini.

Since the genus was first named in the early 19th Century, numerous species have been assigned to Mosasaurus. However, only four are currently recognized as valid by most researchers: M. hoffmannii Mantell 1829 (the type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...

), M. lemonnieri Dollo 1889, M. missouriensis (Harlan 1834), and M. beaugei Armbourg, 1952.

Other named, but invalid or dubious
Nomen dubium
In zoological nomenclature, a nomen dubium is a scientific name that is of unknown or doubtful application...

 species include:

M. copeanus Marsh
Othniel Charles Marsh
Othniel Charles Marsh was an American paleontologist. Marsh was one of the preeminent scientists in the field; the discovery or description of dozens of news species and theories on the origins of birds are among his legacies.Born into a modest family, Marsh was able to afford higher education...

, 1869

M. crassidens Marsh, 1870

M. dekayi Bronn, 1838

M. giganteus (Somering, 1916)

M. gracilis Owen
Richard Owen
Sir Richard Owen, FRS KCB was an English biologist, comparative anatomist and palaeontologist.Owen is probably best remembered today for coining the word Dinosauria and for his outspoken opposition to Charles Darwin's theory of evolution by natural selection...

, 1851

M. hardenponti

M. hobetsuensis Suzuki, 1985

M. johnsoni (Mehl, 1930)

M. lonzeensis Dollo, 1904

M. lundgreni (Schroder, 1885)

M. meirsii Marsh, 1869

M. mokoroa Welles & Gregg, 1971

M. neovidii von Meyer, 1845

M. prismaticus Sakuai, Chitoku & Shibuya, 1999

M. scanicus Schroder, 1885

M. iguanavus (Cope, 1868)

M. poultneyi Martin,1953

External links

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