Archelon

Archelon (from Greek αρχελών meaning ruler turtle) is a genus of extinct sea turtles, the largest genus of sea turtles that has ever been documented, and the second-heaviest turtles documented behind Stupendemys.

 

The largest Archelon fossil measured more than 4 metres long, and about 5 metres  wide from flipper to flipper. It was a marine turtle, whose closest living relative in the present day is the leatherback sea turtle. It lived at a time when a shallow sea covered most of central North America. Most of the known remains have been found in South Dakota and Wyoming. Though anatomically similar to the earlier species Protostega gigas, it was much larger. Unlike most modern turtles, Archelon did not have a solid shell, but instead had a skeletal framework supporting a leathery or bony carapace. Other distinguishing features include a pointed tail, a narrow skull, a relatively narrow, high-vaulted shell, and a pronounced overbite. The live weight of an Archelon is estimated at more than 2200 kg. They probably had a very strong bite, and were optimized for feeding on pelagic mollusc's such as squid.