Platecarpus
Platecarpus | |
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Cast of P. tympaniticus | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | Squamata |
Clade: | †Mosasauria |
Superfamily: | †Mosasauroidea |
Family: | †Mosasauridae |
Clade: | †Russellosaurina |
Subfamily: | †Plioplatecarpinae |
Genus: | †Platecarpus Cope, 1869 |
Species: | †P. tympaniticus
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Binomial name | |
†Platecarpus tympaniticus Cope, 1869
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Synonyms | |
Platecarpus coryphaeus |
Platecarpus ("flat wrist") is an
Description
Platecarpus had a long, down-turned tail with a large dorsal lobe on it, steering flippers, and jaws lined with conical teeth. A complete specimen LACM 128319 shows that it grew up to 5.67 m (18.6 ft) long.[2] The platecarpine mosasaurs had evolved into the very specialized plioplatecarpine group by the end of the Cretaceous.
The skull structure of Platecarpus is unique among mosasaurs. This genus is characterized by a short skull, and has fewer teeth than any other mosasaur (around 10 teeth in each
The
Skin impressions are known from Platecarpus, preserved in LACM 128319 as soft impressions and
Internal organs, or
Part of the digestive tract is also preserved and is filled with mid-sized fish remains. The shape of these remains may outline the true shape of the corresponding part of the digestive tract, most likely the
The caudal, or tail vertebrae, are sharply downturned. The vertebrae at the bend (called the caudal peduncle) are wedge-shaped with neural spines that are wider at their ends than they are at their bases. This downturned area likely supported a fluke similar to modern sharks. Two lobes would have been present, a lower one supported by the downturned vertebrae and an upper, unsupported one. The tail fluke was probably hypocercal, meaning that its lower lobe was longer than its upper lobe. This condition is also seen in
History
Fossils
Various skeletons of this mosasaur have been found in Cretaceous deposits in Kansas, but only one complete skull has ever been recovered.[4] Platecarpus fossils have been found in rocks that date back to the late Santonian through the early Campanian in the Smoky Hill Chalk.
Taxonomic history
Platecarpus was often regarded as the most common genus of mosasaur in the
The cladogram below follows the most resolved topology from a 2011 analysis by paleontologists Takuya Konishi and Michael W. Caldwell.[8]
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Paleobiology
Diet
Compared to the tylosaurs, plioplatecarpine mosasaurs had much less robust teeth, suggesting that they fed on smaller (or softer) prey such as small fish and squid.[4]
Locomotion
While mosasaurs are traditionally thought to have propelled themselves through the water by lateral undulation in a similar way to eels, the deep caudal fin of Platecarpus suggests that it swam more like a shark. The downturned caudal vertebrae of Platecarpus suggest it had a crescent-shaped tail fluke. At the point of the tail where the fluke begins the vertebral centra are shortened and disk-like. Their reduced size likely allowed for greater flexibility at an area that would have experienced high stresses during swimming. The neural spines of these vertebrae also have grooves for the insertion of
The structure of the scales of Platecarpus may have been another adaptation toward a marine lifestyle. The small size and similar shape of these scales throughout the body would have stiffened the trunk, making it more resistant to lateral movement. This stiffness would have improved
Notes
- Demopolis Formationin Alabama that has a lower number of teeth in its jaws.
References
- ^ ISBN 978-1-84028-152-1.
- ^ PMID 20711249.
- .
- ^ a b c d Everhart, Michael J.. Oceans of Kansas: A Natural History of the Western Interior Seaway. c. 2005. pp. 165–169
- ^ Williston (1898a)
- ^ Russell (1967)
- ^ (Everhart and Johnson, 2001)
- ^ S2CID 85972311.
- ^ Lingham-Soliar T. 1994. The mosasaur "Angolasaurus" bocagei (Reptilia: Mosasauridae) from the Turonian of Angola reinterpreted as the earliest member of the genus Platecarpus. Palaeont. Z. 68 (1/2): 267–282.
- ^ Kiernan CR, 2002. Stratigraphic distribution and habitat segregation of mosasaurs in the Upper Cretaceous of western and central Alabama, with an historical review of Alabama mosasaur discoveries. Journal of Vertebrate Paleontology 22 (1): 91–103.
Further reading
Williston 1898 – includes drawings of the skull of Platecarpus ictericus