In order to put together an entire specimen, the missing bones, except for the head, were cast in plaster by Burke employees. Jefferson’s ground sloth received its formal name in 1822, when French anatomist Anselme Demarast named it in honor of Jefferson.Īt present, the Sea-Tac sloth is on display at the Burke Museum. He had seen a paper written by the great French naturalist Georges Cuvier, which convinced Jefferson that his fossil was akin to a giant tree sloth described by the Frenchman. Curiously, a postscript added by Jefferson notes that his initial interpretation of the Megalonyx as a lion was wrong. Jefferson’s paper was not formally published until 1799. Furthermore, Jefferson suggested that the Megalonyx may still be alive in the vast unexplored part of our continent. In a March 10 speech in Philadelphia before the American Philosophical Society, Jefferson referred to a “large animal of the clawed kind,” which he named Megalonyx or “great-claw” (Jefferson). He thought the claws belonged to a lion or tiger, though one three times larger than a modern variety. The bones had been dug out of saltpeter mine (potassium nitrate, a commonly used fertilizer) in Greenbriar County, Virginia (now West Virginia). Jefferson, who had a deep passion for natural history, had received several bones, including the ulna, radius, and claws, from a Colonel John Stewart. Megalonyx jeffersonii holds a unique distinction in the annals of paleontology Vice-President Thomas Jefferson gave the animal its generic epithet in 1797. They could have used their large claws for hooking branches or possibly for defense. They chewed twigs and leaves with short and stout grinding teeth. A post-glacial habitat of forests, lakes, and bogs provided a diverse food supply for large herbivores such as giant ground sloths. The Sea-Tac sloth lived and died sometime between 12,600 and 12,760 years ago, soon after the 3,000-foot-thick Puget Lobe of the Cordilleran ice sheet retreated back to the north. An older sloth, Megalonyx leptostomus, was found in sediments in Eastern Washington dated around 3.5 million years old. It was the first and only fossil find of these sloths discovered in the state. Usually you have to chip old bones out of hardened soil” ( The Seattle Times).īased on the shape of the 45-inch-wide pelvis, as well as the limb bones and claws, Mallory determined that the bones came from the extinct giant sloth known as Megalonyx jeffersonii.

All we have to do to clean them is to put them under the faucet. Coombs, chair of the University of Washington geology department said “You can even see the tiny scars left by muscles. But the bones they do dig up are in great shape. Nor do they find any human-made artifacts. Over the next week, they work with Elmer White of Western Bridge Company to pull up more bones.Īlthough the poor conditions - flooding and collapsing walls in a bog - make the dig difficult, the scientists extract more than 60 percent of the animal’s body.

Paleontologist Stan Mallory and archeologist Robert Greengo from the Burke Museum are called in to investigate. When Simmons finds the bones he stops the dig. A display at the Burke Museum now showcases the discovery, mounted as a complete skeleton. The extinct animal lived around 12,600 years ago and was the size of a Mini Cooper. They find additional bones, eventually totaling about 60 percent of the body of a giant sloth, known as Megalonyx jeffersonii. On Tuesday, February 14, 1961, while working on a runway at Sea-Tac International Airport, Gordon Simmons of Sellen Construction Company spots bones sticking out of a recently excavated 14-foot-deep hole dug for an anchor for a lighting tower. Digging stops and paleontologists from the Burke Museum are called in to investigate.

Sloth skeleton