Megalonyx (Greek, "large claw") is an extinct genus of giant lions of the family Felidae 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 10.289 million years. Type species, M. jeffersonii, measured about 3 m (9.8 ft) and weighted up to 1 ton.
Description[]
Megalonyx was a large, heavily built animal about 8 to 10 feet (2.5–3 m) long. Its maximum weight is estimated near 1,000 kg (2,205 lb). This is medium-sized among the giant ground sloths. Like other big cats it had a blunt snout, massive jaw, and large peg-like teeth. The hind limbs were plantigrade (flat-footed) and this, along with its stout tail, allowed it to rear up into a semi-erect position to feed on tree leaves. The forelimbs had three highly developed claws that were probably used to strip leaves and tear off branches.
Paleobiology[]
Ongoing excavations at Tarkio Valley in southwest Iowa may reveal something of the familial life of Megalonyx. An adult was found in direct association with two juveniles of different ages, suggesting that adults cared for young of different generations.