Within the mosasaur family, the extinct genus Platecarpus (meaning "flat wrist") comprised water lizards that lived between 84 and 81 million years ago, in the middle Santonian to early Campanian epoch of the Late Cretaceous period. There are reports of fossils discovered in the United States, and there may be examples in Belgium and Africa. A well-preserved specimen of Platecarpus indicates that it consumed fish of a modest size. It has also been suggested that it may have consumed ammonites and squid. It was once believed to have swum like an eel, like other mosasaurs, but another study indicates that it swam more like a current shark. The remarkably well-preserved P. tympaniticus specimen known as LACM 128319 exhibits pigments around the nostrils, bronchial tubes, and a high-profile tail fluke, indicating that it and other mosasaurs were more powerful and swift swimmers rather than necessarily having an eel-like swimming style. The Los Angeles County Natural History Museum serves as the venue. Similar to contemporary sea snakes, this species and Clidastes may have occasionally entered freshwater, according to isotope study on tooth fossils.
Description
Platecarpus was characterized by a long, downturned tail, steering flippers, and jaws lined with conical teeth. It also had a huge dorsal lobe on its tail. It reached to a maximum length of 5.67 m (18.6 ft), according to a full specimen, LACM 128319. By the end of the Cretaceous period, the platecarpine mosasaurs had transformed into the highly specialized plioplatecarpine group. Among mosasaurs, Platecarpus's skull structure is distinct. With only ten teeth in each dentary, this genus has fewer teeth than any other mosasaur genus and is distinguished by a small head. Matter within the sclerotic ring, which might potentially constitute the retina of the eye, is preserved by LACM 128319. Through scanning electron microspectroscopy, small, 2 μm-long objects in the retina may be identified as retinal melanosomes that have been retained in their original locations. In LACM 128319, the respiratory tube is also identified as cartilaginous tracheal rings that have been retained. There is knowledge only about the posterior end of the tracheal tube, which is located at the pectoral girdle at the end of the neck. The specimen also had the part where the two bronchi divided, but it was damaged during excavation. This suggests that the lungs of Platecarpus and other mosasaurs were bipedal. Similar to mosasaurs, snakes only have one functioning lung, with the other frequently being missing or just partially developed. But in contrast to terrestrial lizards, the bronchi split anteriorly, before the forelimb region, instead than at the limb level.
History[]
Fossils[]
In Kansas' Cretaceous strata, many skeletons of this mosasaur have been discovered, but only one whole head has ever been retrieved. Fossils of Platecarpus have been discovered in Smoky Hill Chalk strata that span the late Santonian to the early Campanian ages.
Taxonomic History
During the deposition of the Smoky Hill Chalk in Kansas, Platecarpus was frequently considered the most abundant genus of mosasaurs in the Western Interior Sea, with Platecarpus ictericus being considered the most frequently found species. But as of right moment, researchers believe it belongs to the paraphyletic genus. As a result, some species were moved to different genera. Professor B. F. Mudge found the type specimen of Platecarpus planiforns, which Edward Drinker Cope identified as Clidastes planiforns. After the bones were examined more closely in 1898, it was decided to classify the mosasaur under the genus Platecarpus. In 1967, paleontologist Dale Russell conducted another taxonomic evaluation of the original specimen and declared it to be of "uncertain taxonomic position" due to the fragmented nature of the bones, making it difficult to classify it into a genus. A full fossilized skull was uncovered in the Smoky Hill Chalk of Kansas in 2006, which confirmed this location. Takuya Konishi and Michael W. Caldwell created the new genus name Plesioplatecarpus in 2011 to include P. planifrons, which they discovered through phylogenetic research to be different from Platecarpus. This genus was synonymized with Angolasaurus in 1994. Many new research, however, support this genus once again. Moreover, Platecarpus is regarded as monotypic since P. tympaniticus, the type species, was synonymized with P. coryphaeus and P. ictericus.
The topology that has been most resolved in the cladogram below was determined by paleontologists Takuya Konishi and Michael W. Caldwell in 2011.
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Paleobiology[]
Diet
Plioplatecarpine mosasaurs possessed far weaker teeth than tylosaurs, which may have indicated that they consumed smaller or softer food like squid and tiny fish.
Locomotion
Although it is commonly believed that mosasaurs moved through the water by lateral undulation, much like eels, Platecarpus's deep caudal fin indicates that it swam more like a shark. Platecarpus's downturned caudal vertebrae indicate that it possessed a tail fluke with a crescent form. The vertebral centra are shortened and resemble disks at the location on the tail where the fluke starts. Their smaller stature probably made them more flexible in a place where swimming would have put a lot of strain on them. These vertebrae's neural spines also include channels where interspinal ligaments and dorsal connective tissues can enter, which would have let the fluke move laterally. After energy was stored in them, the ligaments—which were most likely composed of collagenous fibers—acted as springs to return the tail to a resting posture. In certain live fish, this kind of ligament helps preserve energy when the tail is repeatedly bent. In Platecarpus, the base of the tail stayed steady while the fluke and rear of the tail fluctuated. Carangiform locomotion is the term for this type of movement.
Restoration of Platecarpus by Dmitry Bogdanov.
Sources[1]