Жоғалған Мегалоникс: Солтүстік Американың алып жануарлары

Extinct genus of ground sloths

Megalonyx (Greek, "great claw") is an extinct genus of ground sloths of the family Megalonychidae, native to North America. It evolved during the Pliocene Epoch and became extinct during at the end of the Late Pleistocene, living from ~5 million to ~13,000 years ago. The type species, M. jeffersonii (also called Jefferson's ground sloth), the youngest and largest known species, measured about in length and weighed up to
Megalonyx is suggested to have descended from Pliometanastes, a genus of ground sloth that had arrived in North America during the Late Miocene around 9 million years ago, prior to the main phase of the Great American Interchange. Megalonyx had the widest distribution of any North American ground sloth, having a range encompassing most of the contiguous United States, extending as far north as Alaska during warm periods. Megalonyx is notable for having been originally described by future U. S. President Thomas Jefferson in 1799 based on remains found in West Virginia, the species M. jeffersonii was described later, named in honor of him. Megalonyx became extinct as part of Late Pleistocene extinctions, simultaneously with all other mainland ground sloths and most other large mammals native to the Americas. These extinctions followed the arrival of humans in the Americas, and there is evidence that humans interacted with Megalonyx, including butchering its remains shortly prior to its extinction.

In 1796, Colonel John Stuart sent Thomas Jefferson, shortly before he took office as Vice President of the United States, some fossil bones: a femur fragment, ulna, radius, and foot bones including three large claws. The discoveries were made in a cave in Greenbrier County, Virginia (presently West Virginia). Jefferson examined the bones and presented his observations in the paper "A Memoir on the Discovery of Certain Bones of a Quadruped of the Clawed Kind in the Western Parts of Virginia" to the American Philosophical Society in Philadelphia on March 10, 1797. The paper was published in 1799, in the same volume as an accompanying paper by his colleague Caspar Wistar, who provided detailed anatomical information about the bones, and illustrated them. Together these two papers are considered the first North American publications devoted to paleontology. In the 1799 paper, Jefferson named the then unknown animal Megalonyx ("great claw") and compared each recovered bone to the corresponding bone in a lion. However, Jefferson's notion that humans and Megalonyx co existed in North America has been shown to be correct, as some bones of Megalonyx show marks made by flint tools. Scientific papers variously give the authority for the genus as Jefferson 1799 (after Jefferson's original naming of the genus), or Harlan 1825. The story came under scrutiny when in 1993 two fragments of a Megalonyx scapula were found in Haynes Cave in neighboring Monroe County. Smithsonian paleontologist Frederick Grady presented evidence in 1995 confirming Haynes Cave as the original source of Jefferson's fossil. Jefferson reported that the bones had been found by saltpeter workers. He gave the cave owner's name as Frederic Crower. Correspondence between Jefferson and Colonel Stuart, who sent him the bones, indicates that the cave was located about five miles from Stuart's home and that it contained saltpeter vats. An investigation of property ownership records revealed "Frederic Crower" to be an apparent misspelling of the name Frederic Gromer. Megalonyx is thought to be descended from Pliometanastes, a ground sloth that arrived in North America during the late Miocene, around 9 million years ago. The earliest representatives of Megalonyx appeared during the Pliocene. through to the Rancholabrean of the Late Pleistocene (11,000 BP). M. jeffersonii was probably descended from M. wheatleyi. The Megalonyx lineage increased in size with time, with the last species M. jeffersonii being the largest. and the Yukon during interglacial intervals. The sloth ranged as far northeast as New York. In 2010, a specimen was discovered at the Ziegler Reservoir site near Snowmass Village, Colorado, in the Rocky Mountains at an elevation of The habitat of Megalonyx jeffersonii was highly variable, but often associated with spruce dominated, mixed conifer hardwood forest.

(1871) Preliminary report on the vertebrata discovered in the Port Kennedy Bone Cave. American Philosophical Society, 12:73 102. (1893) A preliminary report on the vertebrate paleontology of the Llano Estacado. 4th Annual Report on the Geological Survey of Texas: 136pp. (1968) Plio Pleistocene megalonychid sloths of North America. Bulletin of the Florida State Museum Biological Sciences, 12(5):213 296.