The lizard from the Meuse river.
There is a huge marine reptile mounted in the Havard Natural History Museum. But not to be confused with another marine reptile appeared in a recent movie.
The one in the movie is Mosasaurus, which is from one of the 38 genera of Mosasaurs. Mosasaurs literally means Meuse reptile, or lizards. The Meuse river is where their first fossil remains were discovered. Recent research indicated that Mosasaurs swam like sharks and were endothermic and viviparous.
The one in the museum is Kronosaurus, one genus from Pliosauroidae. The pliosaurs were short-necked plesiosaurs, as indicated by the plio prefix, and were distant cousins of modern turtles. The pliosaurs had large heads and massive toothed jaws and swum like a turtle. Interestingly, the specimen in Havard is probably reconstructed with too many vertebrae.
Mosasaurus and Kronosaurus do have common relatives in the evolutionary tree. To start with, they both belong to class Sauropsida, “lizard faces”, including all existing birds and reptiles and their extinct relatives. Note that there is a class Reptilia for reptiles, semi-deprecated due to the advent of phylogenetic nomenclature. Then clade Eureptilia, “true reptiles”, characterized by two disconnected groups of bones in the skull. Then clade Diapsida, “two arches”, the only clade that survives through the Permian period, characterized by two holes in the skull. Then clade Neodiapsida, “new two arches”, including all the diapsids since the early Permian period. Finally, the clade Sauria, a crowned-group of all modern reptiles including birds (and their extinct relatives of course).
Sauria divides into two clades. One is Lepidosauromorpha, “scaled lizard forms”, including all diapsids closer to lizards than to crocodiles and birds. The other is Archosauromorpha, “ruling lizard forms”, including the rest diapsids in Sauria. Mosasaurus belongs to the order Squamata, containing scaled reptiles comprising all lizards and snakes. Squamata belongs to the clade Lepidosauria under Lepidosauromorpha, “scaled lizards”, i.e. reptiles with overlapping scales. Kronosaurus under Plesiosauria belongs to clade Sauropterygia, “lizard flippers”, aquatic reptiles swimming with flippers. Sauropterygia belongs to the clade Pantestudines under Archosauromorpha, containing tetrapods more closely related to turtles.
During the late Cretaceous period, with the extinction of the ichthyosaurs and pliosaurs, mosasaurs became the dominant marine predators. So it is a little wired that a Cretaceous creature appeared in a movie themed Jurassic period.
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