Tuesday, October 5, 2010

October 5, 2010 : Platecarpus (Extinct)


Platecarpus ("Flat wrist") is an extinct genus of aquatic lizard belonging to the mosasaur family, living around 75 million years ago during the end of the Cretaceous period. Fossils have been found in Belgium and the United States as well as a possible specimen in Africa.
Platecarpus probably fed on fish, squid, and ammonites. Like other mosasaurs, it was initially thought to have swum in an eel-like fashion, although a recent study suggests that it swam more like modern sharks. An exceptionally well-preserved specimen of P. tympaniticus known as LACM 128319 shows skin impressions, pigments around the nostrils, bronchial tubes and the presence of a high profile tail fluke, showing that it and other mosasaurs did not necessarily have an eel-like swimming method but were more powerful fast swimmers. It is held in the Natural History Museum of Los Angeles County.

Platecarpus had a long, down-turned tail with a large dorsal lobe on it, steering flippers, and jaws lined with conical teeth. It grew up to 4.3 metres (14 ft) long, with half of that length taken up by its tail. The platecarpine mosasaurs had evolved into the very specialized plioplatecarpine group by the end of the Cretaceous.

Platecarpus was probably the most common genus of mosasaur in the Western Interior Sea during the deposition of the Smoky Hill Chalk in Kansas, and
Platecarpus ictericus is the most commonly occurring species. There is some controversy regarding the description of the genus Platecarpus since it includes some diverse, and possibly unrelated forms.

The type specimen of Platecarpus (P. planiforms) was discovered by Professor B. F. Mudge and was classified by Edward Drinker Cope as Clidastes planiformes. In 1898, on further analysis of the remains, it was determined that the mosasaur be placed in a separate genus, Platecarpus. The type specimen underwent another taxonomic review in 1967, when paleontologist Dale Russell determined that the remains were too fragmentary to be placed within any genus, and deemed it to be a specimen of "uncertain taxonomic position". A 2006 discovery in the Smoky Hill Chalk of Kansas re-affirmed this position with the discovery a complete fossilized skull being unearthed.

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