STL Science Center

STL Science Center

08 February 2013

Not Quite Stupendemys

Stupendemys, for those of the readers not in the know, is a genus of turtle, extinct, that is now considered the largest in the history of the world. This week we will cover what is now the second largest turtle, also extinct (for this blog? of course!), called Archelon ischyros. A major difference between these two turtles, besides size, is that Stupendemys was a fresh water turtle whereas Archelon was a sea turtle. Archelon was not the first sea turtle, and obviously not the last, but it still is the largest marine turtle and at over 4m (13ft) tip of the beak to tip of the tail and just about 4.9m (16ft) from flipper-tip to flipper-tip, it may have weighed over 2,200kg (4,900lbs). To put that in perspective, the largest living turtle, the Leatherback sea turtle (Dermochelys coriacea) is at its largest 2.2 m (7.2 ft) from beak to tail, 1.75m (5.74 ft) from flipper to flipper, and weighs up to 700 kg (1,500 lb). That makes Archelon a little more than twice as long, nearly three times as wide, and three times as heavy as the largest living turtle!

Oh, hi! from Wallace Building on the University of Manitoba campus, Winnipeg, Manitoba Canada (Photo by: Mike Beauregard, taken from Wikicommons)
Archelon was unusual amongst turtles in that its shell was not a shell; rather it was a scaffold of strong bony struts that supported a leathery/bony (debatable point here) carapace above it. It has large flippers, a nice sharp looking beak with an overbite almost more akin to a parrot than an extant turtle, and is thought to have used that beak to crush mollusks. Leatherbacks dine on jellyfish and other related pelagic goodies, but their ancient suborder (both Archelon and Leatherbacks belong to the Cryptodira suborder of Testudines) cousins were crunching enormous squid and possibly ammonites. More to come on shells, beaks, and the size of this behemoth!

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