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Megalonyx (Greek, "great claw") is an extinct genus of giant ground sloths of the family Megalonychidae endemic to North America from the Hemphillian of the Late Miocene through to the Rancholabrean of the Pleistocene, living from 10.3million years ago - 11,000 years ago, existing for approximately 10.2 million years. The generic name Megalonyx was proposed by future U.S. President Thomas Jefferson in 1797, based on fossil specimens of what later came to be called Megalonyx jeffersonii that he had received from western Virginia. His presentation to the American Philosophical Society that year is often credited as the beginning of vertebrate paleontology in North America. However, Jefferson's name has no validity in zoological nomenclature, and Megalonyx was first formally named by Richard Harlan in 1825. Megalonyx ranged over much of North and Central America. Their remains have been found as far north as Alaska and the Yukon.







