Plotosaurus

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Plotosaurus
Temporal range: Maastrichtian, 70.6–66.0 Ma
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Plotosaurus LACM.png
Mounted skeleton (LACM CIT 270) at the Los Angeles County Natural History Museum
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Superfamily: †Mosasauroidea
Family: †Mosasauridae
Tribe: †Mosasaurini
Genus: †Plotosaurus
Camp, 1951
Type species
†Plotosaurus bennisoni
Camp, 1942
Species

See text

Synonyms[1]
  • Kolposaurus Camp, 1942
  • Garzasaurus Anderson, 1943

Plotosaurus ("swimmer lizard") is an extinct genus of mosasaur from the Upper Cretaceous (Maastrichtian) of Fresno County, California. Originally named Kolposaurus (meaning "bay lizard") by Berkeley paleontologist Charles Lewis Camp in 1942, it was changed to Plotosaurus in 1951 when Camp discovered the name had already been assigned to a type of nothosaur.

Description[]

Restoration of P. bennisoni

Plotosaurs possessed several adaptations to marine life not seen in other mosasaurs. Compared with their relatives, they had narrower flippers, large tail fins and a streamlined fusiform body shape.[2] This design converges with the morphology and hydrodynamic build of ichthyosaurs. Some of the tail vertebrae are fused together; unlike in most mosasaurs this is not a pathological condition but another aquatic adaptation that allowed Plotosaurus to achieve a more efficient swimming design. Altogether, Plotosaurus possessed the highest level of aquatic adaptations in any mosasaur.[3] These features probably enabled them to also be one of the fastest of the mosasaurs.[4] They also had relatively large eyes for keen eyesight, and impressions found with their fossils suggest that they had scaly skin.[2]

Based on cladistic analysis, plotosaurs are considered to be the most derived branch of mosasaur evolution.[citation needed]

Species[]

The type species, P. bennisoni, was named for Allan Bennison, a fossil hunter who discovered the first remains in 1937. It was around 9 metres (30 ft) long, and was the first known mosasaur from California (a year previously, Bennison had also discovered the state's first dinosaur, a species of Saurolophus that is now known as Augustynolophus).

A second species, P. tuckeri, was proposed in 1937 by Frank Paiva and Professor William M. Tucker. Although not quite as advanced in aquatic adaptations as P. bennisoni, it was about 40% larger, reaching lengths of around 13 metres (43 ft).[citation needed] However, a recent analysis by Lindgren, Caldwell and Jagt (2008) considers P. tuckeri to be a junior synonym of P. bennisoni.

Palaeobiology[]

Plotosaurus is considered to have the highest levels of aquatic adaptations among mosasaurs.[3]

Studies of Plotosaurus indicate that the animal utilized its pectoral flippers to aid in creating added bursts of speed when attacking prey, utilizing a breaststroke motion, based on the large muscle attachments on the pectoral girdle and asymmetry of the mosasaur's bone structure.[5]

References[]

  1. ^ Plotosaurus at fossilworks.org
  2. ^ Jump up to: a b Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 87. ISBN 1-84028-152-9.
  3. ^ Jump up to: a b Lindgren, J., Jagt, J.W.M., and Caldwell, M.W. 2007. A fishy mosasaur: the axial skeleton of Plotosaurus (Reptilia, Squamata) reassessed. Lethaia 40:153-160.
  4. ^ Rothschild, B.; Everhart, M.J. (2015). "Co-Ossification of Vertebrae in Mosasaurs (Squamata, Mosasauridae); Evidence of Habitat Interactions and Susceptibility to Bone Disease". Transactions of the Kansas Academy of Science. 118 (3&4): 265–275. doi:10.1660/062.118.0309.
  5. ^ https://www.sciencedaily.com/releases/2019/09/190923140812.htm
  • Camp, C.L. 1942. California Mosasaurs. Memoirs of the University of California 13:1-68.
  • Camp, C.L. 1951. Plotosaurus, a new generic name for Kolposaurus Camp, preoccupied. Journal of Paleontology 25:822.
  • Hilton, R.P. 2003. Dinosaurs and Other Mesozoic Reptiles of California. Berkeley and Los Angeles: University of California Press, 356 pp. ISBN 0-520-23315-8
  • Lindgren, J., Caldwell, M.W. and Jagt, J.W.M. 2008. New data on the postcranial anatomy of the California mosasaur Plotosaurus bennisoni (Camp, 1942) (Upper Cretaceous: Maastrichtian), and the taxonomic status of P. tuckeri (Camp, 1942). Journal of Vertebrate Paleontology 28(4):1043-1054.
  • Lindgren, J., Alwmark, C., Caldwell, M.W., and Fiorillo, A.R. 2009. Skin of the Cretaceous mosasaur Plotosaurus: implications for aquatic adaptations in giant marine reptiles. Biology Letters doi:10.1098/rsbl.2009.0097.

External links[]

  • Mosasauridae Translation and Pronunciation Guide [1]
  • Natural History Museum of Los Angeles County [2]
  • UCMP Paleontology Portal [3]


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