Temporal range: Pliocene-Late Pleistocene (Hemphillian-Rancholabrean) 5–0.013 Ma
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M. wheatleyi skeleton in AMNH
Scientific classification
Domain:
Eukaryota
Kingdom:
Animalia
Phylum:
Chordata
Class:
Mammalia
Order:
Pilosa
Family:
†Megalonychidae
Subfamily:
†Megalonychinae
Genus:
†Megalonyx Jefferson, 1799[1]
Type species
†Megatherium jeffersonii[1]
Desmarest, 1822
Species
†M. jeffersonii (Desmarest, 1822)
†M. leptostomusCope, 1893
†M. matthisiHirschfeld & Webb, 1963
†M. obtusidensWebb & Perrigo, 1985[2]
†M. wheatleyiCope, 1871
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.[3] The type species, M. jeffersonii (also called Jefferson's ground sloth), the youngest and largest known species, measured about 3 meters (9.8 ft) in length and weighed up to 1,000 kilograms (2,200 lb).[4]
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.[1]
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.
^ abcBabcock, Loren E. (18 March 2024). "Nomenclatural history of Megalonyx Jefferson, 1799 (Mammalia, Xenarthra, Pilosa, Megalonychidae)". ZooKeys (1195): 297–308. doi:10.3897/zookeys.1195.117999. ISSN 1313-2970. PMC 10964019. PMID 38532771.
^Megalonyx obtusidens at Fossilworks.org
^McDonald, H. Gregory; Stafford, Thomas W.; Gnidovec, Dale M. (March 2015). "Youngest Radiocarbon Age for Jefferson's Ground Sloth, Megalonyx Jeffersonii (Xenarthra, Megalonychidae)". Quaternary Research. 83 (2): 355–359. Bibcode:2015QuRes..83..355G. doi:10.1016/j.yqres.2014.11.006. S2CID 129016865. Retrieved 2021-05-23.
^"Sandiegozoo". Archived from the original on 2015-02-14. Retrieved 2012-05-30.
Megalonyx (Greek, "great-claw") is an extinct genus of ground sloths of the family Megalonychidae, native to North America. It evolved during the Pliocene...
engaged in long-term parental care, with one adult (presumably female) Megalonyx found with two juveniles of different ages, with the oldest juvenile suggested...
Kimmeridge Clay Formation of England. The type species, Gigantosaurus megalonyx, was named and described by Harry Govier Seeley in 1869. Its syntype series...
Megalonychidae is an extinct family of sloths including the extinct Megalonyx. Megalonychids first appeared in the early Oligocene, about 35 million years...
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Mexico to Honduras, and Panama. C. andicola, C. audax, C. ursinus and C. megalonyx are known from Colombia and further into South America. Cheliomyrmex andicola...
to mylodontids and three-toed sloths within Megatherioidea, close to Megalonyx, megatheriids and nothrotheriids. They make the previously recognized...
a cave in western Virginia and named the genus (Megalonyx). The species was ultimately named Megalonyx jeffersonii in his honor. Jefferson corresponded...
reported on the skeletal remains of an extinct large sloth, which he named Megalonyx, unearthed by saltpeter workers from a cave in what is now Monroe County...
April 2023. Johan Harold Josua Lindahl (1893). Description of a Skull of Megalonyx Leidyi, page 56 (American Philosophical Society) "The Online Etymological...
them as being from a genus unknown to science and named the creature Megalonyx. The cave from which these fossils were taken later came to be identified...
with a few other mammalian faunas, namely the megalonychid ground sloth Megalonyx, the pocket gopher Geomys, the cricetid Sigmodon, the equin Equus, the...
soldier Colonel John Stuart to Thomas Jefferson. The bones were named Megalonyx jeffersonii, or great-claw, and became known as Jefferson's three-toed...
of ground sloths including Megalocnus rodens, Scelidotherium cuvieri, Megalonyx wheatleyi and Glossotherium robustus A Triceratops and a Stegosaurus are...
Rancholabrean NALMA (240,000 BCE to 11,000 BCE), the last surviving genus being Megalonyx itself from North America. Megalonychids were long-considered to be an...
paleontologist Richard Harlan identified a new species of giant sloth, Megalonyx laqueatus, from bones found at Big Bone Lick. In 1840, the species was...
rest of the bones found at the locality form the paratype Gigantosaurus megalonyx Syntypes: CAMSM J.29477 to J.29483 Sedgwick Museum of Earth Sciences Kimmeridgian...
in the Megalonychidae alongside two-toed sloths and ground sloths like Megalonyx, recent mitochondrial DNA and collagen sequencing studies place them as...
paleontologist Joseph Leidy he described it as a new species of the large Megalonyx, Megalonyx rodens, though stated that it could be a different genus, which he...
lions, ground sloths (predominantly Paramylodon harlani, with much rarer Megalonyx jeffersonii and Nothrotheriops shastensis), coyotes, ancient bison, and...
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