The Yale Peabody Museum’s specimen Archelon ischyros Wieland 1896 (YPM 3000) in the Great Hall was the first specimen — and is still one of the largest and most complete — of this species of ancient turtle ever found. This photograph of George R. Wieland standing beside the Archelon skeleton (mount finished in 1907) in the old Peabody Museum building was taken on November 3, 1914.

The skeleton measures about 11 feet from snout to tail (more than 3 meters), and about 15 feet (4.5 meters) from the tip of one fore paddle to the other. Comparisons with the most similar and largest modern turtle, Dermochelys, suggest that Archelon weighed over 3 tons. When collected by the Museum’s 1895 expedition to the Black Hills of South Dakota, only the skull and the right front paddle had been eroded away. Casts based on a second specimen found in the same formation two years later were used to replace these missing pieces.

Archelon was probably not a ferocious predator of the Cretaceous seas. Modern sea turtles are omnivorous, eating seaweed and algae as well as invertebrates and fish. Dermochelys lives predominantly on a diet of jellyfish. Archelon’s great size probably meant that it could not chase down active swimming animals. Its jaws are equipped with broad crushing surfaces and the most strongly curved beak of any turtle, giving it a formidable bite that may have allowed it to subsist on a diet of crustaceans and mollusks like the four-foot long clam Inoceramus, also found with Archelon.