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Description
Megalonyx jeffersoni, also known as the Jefferson's Ground Sloth, was a medium-sized species of ground sloth from the Middle to Late Pleistocene of North America. It was part of the diverse array of giant ground sloths which inhabited the Americas throughout the Pleistocene, till their extinction around 11kya. Megalonyx itself actually has a rather unique evolutionary history. Many other ground sloths only arrived in North America around the time of the Great American Biotic Interchange (GABI), which saw species from South America migrating up into North America and vice versa after the formation of the Isthmus of Panama. But with megalonychids (the family that Megalonyx was in), it's much smaller, meter-tall ancestor Pliometanastes managed to make it to North America during the Late Miocene via island-hopping up through the Central American Seaway to reach North and Central America. This gave rise to Megalonyx, which first appeared in the Pliocene (although the main Pleistocene species jeffersoni did not appear till the middle of the Pleistocene.)

Towards the middle of the spectrum in terms of ground sloth size, Megalonyx grew to around 2 meters tall at the shoulder and had a maximum weight of around 1 ton. While not too large in comparison to other gigantic ground sloths of its day, such as the 2-to-5-ton Megatherium americanum and the colossal 3-to-10-ton Eremotherium laurillardi, Megalonyx was still certainly nothing to scoff at. It was extraordinarily thick-set and robust, with a big chest and possessed hugely strong, muscley limbs. Big bones and a barrel-like chest helped to support the great bulk of the beast. The snout of this ground sloth was shorter and flatter than the longer snout of some other species such as Nothrotheriops. Megalonyx had unique locomotion in comparison to other ground sloths. Instead of walking on the sides of their feet like mylodontids or megatheres, Megalonyx walked on the knuckles of their forelimbs and the soles of their back feet, unusual in comparison to most other ground sloths. It possessed 4 large claws on the hands, and 3 on the back feet. Like other ground sloths, Megalonyx was capable of rearing up on its hind legs, using it's short yet thick and muscular tail to support itself. Throughout its vast range, Megalonyx most definitely possessed a sizable coat of fur. Though, the length of this most likely varied geographically, with individuals in the far north having quite the shaggy coat, while further south and in more temperate climates it would be shorter.

Megalonyx had one of the widest distributions of any ground sloth. It ranged across the eastern and parts of the western United States, going as far south as Mexico. It was seemingly more common in the eastern US than in the West, where other ground sloths such as Paramylodon and Nothrotheriops were more frequent. Megalonyx was the most north-reaching ground sloth of them all, managing to go as far north as the Yukon during the interglacial periods. Its range expanded and contracted depending on the glacial/interglacial period. Ranging over such a wide area, Megalonyx inhabited a wide variety of habitats. It seemed to prefer more forested/wooded areas, mainly temperate deciduous woodlands and boreal forests/swamps. Though, they also ranged into some relatively dry and hot woodland/shrubland regions.
Ecologically, Megalonyx was a forest-dwelling folivore, feeding primarily on leafier plants. Long arms and claws likely made for very helpful tools in acquiring these kinds of foods. Occasional omnivory may be plausible in the northern populations, where plant resources weren't as abundant and high-quality. This sloth was likely not as social as some other ground sloths like Paramylodon, probably being solitary or groupings being restricted to just mothers and their young.
Megalonyx coexisted with a wide range of other megafaunal animals. Some of these included the stag-moose Cervalces, the giant beaver Castoroides, horses, mastodons, and mammoths. They shared range with some ground sloths such as Paramylodon, which they likely niche partitioned with, since Paramylodon preferred more open habitats than Megalonyx. They also coexisted with many predators, including the dire wolf Aenocyon, North American jaguars, and the saber cat Smilodon. All of these most definitely preyed upon the giant sloth. Though, make no mistake, it would be no easy feat to bring one down. Immense bulk would make the sloth difficult to restrain and wound. The ability to rear up gave it extra mobility and likely served as an intimidation tactic, and the large claws on its forearms could most certainly injure or kill any predator that tries to attack it. The sloth was also likely capable of surprising speed for its size and was perhaps able to charge at predators in short bursts, like a gorilla or a bear. Most hunters would probably prefer immature individuals, but many an adult Megalonyx likely fell prey to hunters such as Smilodon.

Description
Megalonyx jeffersoni, also known as the Jefferson's Ground Sloth, was a medium-sized species of ground sloth from the Middle to Late Pleistocene of North America. It was part of the diverse array of giant ground sloths which inhabited the Americas throughout the Pleistocene, till their extinction around 11kya. Megalonyx itself actually has a rather unique evolutionary history. Many other ground sloths only arrived in North America around the time of the Great American Biotic Interchange (GABI), which saw species from South America migrating up into North America and vice versa after the formation of the Isthmus of Panama. But with megalonychids (the family that Megalonyx was in), it's much smaller, meter-tall ancestor Pliometanastes managed to make it to North America during the Late Miocene via island-hopping up through the Central American Seaway to reach North and Central America. This gave rise to Megalonyx, which first appeared in the Pliocene (although the main Pleistocene species jeffersoni did not appear till the middle of the Pleistocene.)

Towards the middle of the spectrum in terms of ground sloth size, Megalonyx grew to around 2 meters tall at the shoulder and had a maximum weight of around 1 ton. While not too large in comparison to other gigantic ground sloths of its day, such as the 2-to-5-ton Megatherium americanum and the colossal 3-to-10-ton Eremotherium laurillardi, Megalonyx was still certainly nothing to scoff at. It was extraordinarily thick-set and robust, with a big chest and possessed hugely strong, muscley limbs. Big bones and a barrel-like chest helped to support the great bulk of the beast. The snout of this ground sloth was shorter and flatter than the longer snout of some other species such as Nothrotheriops. Megalonyx had unique locomotion in comparison to other ground sloths. Instead of walking on the sides of their feet like mylodontids or megatheres, Megalonyx walked on the knuckles of their forelimbs and the soles of their back feet, unusual in comparison to most other ground sloths. It possessed 4 large claws on the hands, and 3 on the back feet. Like other ground sloths, Megalonyx was capable of rearing up on its hind legs, using it's short yet thick and muscular tail to support itself. Throughout its vast range, Megalonyx most definitely possessed a sizable coat of fur. Though, the length of this most likely varied geographically, with individuals in the far north having quite the shaggy coat, while further south and in more temperate climates it would be shorter.

Megalonyx had one of the widest distributions of any ground sloth. It ranged across the eastern and parts of the western United States, going as far south as Mexico. It was seemingly more common in the eastern US than in the West, where other ground sloths such as Paramylodon and Nothrotheriops were more frequent. Megalonyx was the most north-reaching ground sloth of them all, managing to go as far north as the Yukon during the interglacial periods. Its range expanded and contracted depending on the glacial/interglacial period. Ranging over such a wide area, Megalonyx inhabited a wide variety of habitats. It seemed to prefer more forested/wooded areas, mainly temperate deciduous woodlands and boreal forests/swamps. Though, they also ranged into some relatively dry and hot woodland/shrubland regions.
Ecologically, Megalonyx was a forest-dwelling folivore, feeding primarily on leafier plants. Long arms and claws likely made for very helpful tools in acquiring these kinds of foods. Occasional omnivory may be plausible in the northern populations, where plant resources weren't as abundant and high-quality. This sloth was likely not as social as some other ground sloths like Paramylodon, probably being solitary or groupings being restricted to just mothers and their young.
Megalonyx coexisted with a wide range of other megafaunal animals. Some of these included the stag-moose Cervalces, the giant beaver Castoroides, horses, mastodons, and mammoths. They shared range with some ground sloths such as Paramylodon, which they likely niche partitioned with, since Paramylodon preferred more open habitats than Megalonyx. They also coexisted with many predators, including the dire wolf Aenocyon, North American jaguars, and the saber cat Smilodon. All of these most definitely preyed upon the giant sloth. Though, make no mistake, it would be no easy feat to bring one down. Immense bulk would make the sloth difficult to restrain and wound. The ability to rear up gave it extra mobility and likely served as an intimidation tactic, and the large claws on its forearms could most certainly injure or kill any predator that tries to attack it. The sloth was also likely capable of surprising speed for its size and was perhaps able to charge at predators in short bursts, like a gorilla or a bear. Most hunters would probably prefer immature individuals, but many an adult Megalonyx likely fell prey to hunters such as Smilodon.