The Collaborative International Dictionary
Megalonyx \Meg`a*lon"yx\, n. [NL., from Gr. me`gas, mega`lh, great + 'o`nyx claw.] (Paleon.) An extinct quaternary mammal, of great size, allied to the sloth.
Wiktionary
n. (context paleontology English) An extinct quaternary mammal, of great size, allied to the sloth.
Wikipedia
Megalonyx ( Greek, "large claw") is an extinct genus of 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 ~10.3 Mya—11,000 years ago, existing for approximately . Type species, M. jeffersonii, measured about 3 m (9.8 ft) and weighted up to 1000 kilograms.
Usage examples of "megalonyx".
They overestimated its size by a factor of six and gave it frightening claws, which in fact came from a Megalonyx, or giant ground sloth, found nearby.