Plate by Laurillard engraved by Couet together with french Text 'On the Megalonix', both pages from Cuvier's 1812 \Ossamens Fossiles\". Thomas Jefferson (the American founding father and President) made his chief contribution to science in describing (1797) the first fossil of the giant ground sloth Megalonyx jeffersonii from West Virginia. Megalonyx means \"giant claw\" (Fig 1. here). Cuvier credited the discovery to Jefferson and produced this illustration. French naturalist Buffon had earlier been dismissive of the American fauna as feeble, and Jefferson was happy to disprove it. Meglonyx followed the 1789 discovery, in Paraguay, of a near relative, Megatherium. Joseph Leidy produced the most complete description of Megalonyx jeffersonii in his 1855 monograph. Jefferson also described the first American Mastodon which Cuvier featured."