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Description
Megalonyx jeffersonii

Ground sloths were among the most unique of all Pleistocene megafauna. Evolving in South America, they were the first South American megafauna to reach North America 9-10,000,000 years ago, millions of years before the first proper immigrants from the southern continent. They made it to the continent by island hopping from island to island in the Gulf of Mexico. The family Megalonychidae was among the most diverse of all ground sloth families, and its type species, Megalonyx jeffersonii, the Jefferson's Ground Sloth, was the most successful and wide-ranging of all ground sloths.

History and A President's Find:

In 1796, Colonel John Stuart sent then Vice President-Elect Thomas Jefferson a fossil femur fragment, ulna, radius, and three massive claws. They were discovered in Greenbrier County in Virginia (now West Virginia). Thomas Jefferson examined the bones, and in 1797, in a paper he presented to the American Philosophical Society (APS) in Philadelphia, he named them "Megalonyx," meaning "giant or great claw" in Greek. However, he never gave a diagnosis as to what this animal was. He at first attributed this to a lion and even noted in the paper to APS "that he was more than three times as large as the lion." However, in the postscript of his paper, he noted a similarity to an animal recently discovered in Paraguay called Megatherium, a gigantic sloth weighing in at around 4 tons.

However, in 1799, Caspar Wistar, an American anatomist, correctly attributed the bones to a sloth, not a lion. He drew drawings of the claws in 1799. These were among the first illustrations of any vertebrate fossil in North America. Over two centuries later, these still survive in the APS in Philadelphia today. Jefferson subsequently thought this giant claw did not belong to a lion but rather an organism similar to Megatherium.

Extinction was an emerging view in natural history. However, Thomas Jefferson was a man who believed in the "completeness of nature." He thought that nature or the creator (Jefferson was a deist) would not let there be an imbalance in nature and allow a creature die off. When he became President, Jefferson had told the explorers Meriwether Lewis and William Clark to find evidence of live animals in the western United States. Of course, this made no headway, and no living specimens were discovered/described by the expedition.

In 1822, some 23 years after Wistar identified the bones, he proposed naming this species "Megalonyx jeffersonii". French anatomist Anselme Gaëtan Desmarest described it first during that same year, but Richard Harlan, an American naturalist, formally described it in 1825.

Taxonomy and Evolution:

The Megalonyx genus had a variety of species throughout its 10,000,000-year reign. Its sister species, "M.leptostomus" lived till around 250,000 years ago and was around half the size of Jefferson's Sloth. Another species, which evolved from M.leptostomus evolved into M.wheatleyi, even bigger than the preceding species. But the last, biggest, and most widespread of all was the type species, Jefferson's Ground Sloth.

Megalonyx jeffersonii is a member of the Megalonychidae family of pilosans. They're a family within the superfamily Megatheroidea which includes animals like Eremotherium, Megatherium, and Nothrotheriops (the Shasta Ground Sloth). According to recent studies, the closest modern cousins are the three-toed sloths, in fact according to molecular DNA studies both Megalonychids and three-toed sloths' family Bradypodidae are sister families within Megatheroidea.

By the end of the Pleistocene, a variety of genera would thrive across the environment. From the similarly sized Ahytherium of Brazil, and the black bear-sized Xibalbaonyx of Mexico. However, as previously stated, across Mexico, Canada, and America was Megalonyx jeffersonii.

Description:

It was fairly average size for a ground sloth. Around 10ft long and weighing in at around a ton. At the shoulder it would have stood between four and four-and-a-half feet tall. Compared to other ground sloths it had a more squared off head compared to other ground sloths, broadened peg-like teeth designed to process plant material. Its likely that the broadened skull would have enabled a broader diet in their habitat. Among the most iconic feature was the massive claws used for manipulating branches and for defense. The hind limbs ended in feet that were flattened on the side and tipped with three toes. Finally, they had a muscular tail they could have used as a prop to rear back on their hind limbs.

Habitat and Behavior:

Fossils of this species range from as far south as Southern Mexico and as far north as Yukon and into Alaska. The Jefferson's Ground Sloth was the only species of ground sloth to reach Alaska. Their numbers in the far north in regions like Yukon and Alaska were likely because they could have reached the regions during interglacial intervals of the last Ice Age. Also, this genus was the first group to reach North America so they had far more time to adapt to the regions.

As far as habitats go, these animals thrived in almost every environment that they dwelled in. Be it the scrubland of Arizona, Northern and Central Mexico, the grassland prairies of Kansas and Idaho, and the Rocky Mountain States of Utah and Colorado. However, most specimens have been found in forested coniferous environments, with Spruce Trees being the most dominant foliage in the area. Regions like La Brea in California and fossil sites in Illinois and Ohio have also been found.

In a 2013 paper, it was found that the Megalonyx genus would have had a woodland or forest-oriented browser. It would have consumed woody plants, oak trees, and other woody branches like spruce trees. Furthermore, it indicated that in parts of the American South, the sloth and various proboscideans would have browsed upon the Osage oranges, a unique fruit found in parts of Texas and Oklahoma. Nowadays, few browsing animals can consume it, so it just rots away, an example of anachronistic evolution as no browsers can consume it.

Furthermore, white-tailed deer fossils in western Iowa have been found alongside these sloths. It has been theorized that these two forest-going animals stuck together for mutual protection. However, there is no way to thoroughly verify that, as they could have just encountered each other and passed each other by in the forest.

They were filling the niche of the large browsing animal eating different plants in its habitat. Rearing up, they would have towered over most animals in their habitats. Only their giant relative, Eremotherium and proboscideans, could have been taller in their environments.

By studying the only terrestrial pilosan alive today, the giant anteater, it could be extrapolated that these giant sloths carried their babies on their backs until they were old enough to walk alongside their mothers. Their massive torsos would have made for an excellent spot to rest and stay safe from any potential predators.

Fossils found in Iowa have shown evidence of parental care and even extended social behavior in these sloths. An adult individual was found in direct association with two smaller individuals with paleontologists theorizing that varying generations caring for their young.

As far as ground sloths go, these were large, but they may not have been entirely untouchable. Predators like the American Lions, Smilodon (saber-toothed cats), and packs of Dire Wolves could have hunted and killed these animals, especially since it is believed some of these predators hunted in packs. Also, Short-Faced Bears could have preyed upon these sloths occasionally, too.

However, above all, there was one animal that could've easily hunted them and hunted them to a degree that would mean the end of these awe-inspiring animals.

Extinction:

These sloths along with countless other megafauna would vanish around 10-11,000 years ago. Why they went extinct is largely believed to have been due to both climate change and human hunting. A fossil femur of a Jefferson's Ground Sloth found near Snowmount Village (near Aspen) in Colorado has shown evidence of human butchery dated to around 13,000 years ago. In Ohio, a nearly complete specimen was found with evidence of butchery as well.

Ground sloths would persist in the Caribbean for the next few thousand years with Megalocnidae in Hispanola, Puerto Rico and Cuba, but by ~1600-1550 BCE, none would be left on the planet.

Despite the fact that this sloth had gone extinct some 11,000 years ago, its mark on paleontology and history is undeniable. Thomas Jefferson's description of this animal is largely credited as being the beginning of American Paleontology. And the find was not a dinosaur or a marine reptile, but a sloth.
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One of the most iconic sloths found in North America and I feel it needed to be redone again.

It was made by LazardiK and his Sloth pack as I said in the previous profile.

I modified the skull some more and gave it a baby model as well. Plus it was made before I got a handle on the sloth rig so it needed to be reposed rig-wise as well.

As I said before, this guy does great Paleoart:
Ground Sloths 2 - Megalonychids by artbyjrc on DeviantArt

FYI: The paper where I referenced the white-tailed deer was here:
A Ground Sloth, Megalonyx, from a Pleistocene Site in Darke Co., Ohio (core.ac.uk)

I also wanted to depict white-tails alongside them too so I added them to the profile and made it two mothers with their babies.

Will this be used in Past Meets Present? Ahhhh... now I'm not so sure...

There will be ground sloths in season 2, but I've got quite a few already in the episode featuring ground sloths and I really don't want to oversaturate the episode with sloths as cool as they are. I'd say 40% no as I've already got a good candidate to fill a similar niche.

I am working on some more profiles, but work and PMP has kind of slowed me down.

Original model and skin by LazardiK :
Jefferson's Ground Sloth (Lazardi) | ZT2 Download Library Wiki | Fandom

White-Tailed Deer by ZTABC:
White-tailed Deer (ZTABC Team) | ZT2 Download Library Wiki | Fandom

For Past Meets Present:
Past Meets Present - Page 5 - The ZT2 Round Table

Description
Megalonyx jeffersonii

Ground sloths were among the most unique of all Pleistocene megafauna. Evolving in South America, they were the first South American megafauna to reach North America 9-10,000,000 years ago, millions of years before the first proper immigrants from the southern continent. They made it to the continent by island hopping from island to island in the Gulf of Mexico. The family Megalonychidae was among the most diverse of all ground sloth families, and its type species, Megalonyx jeffersonii, the Jefferson's Ground Sloth, was the most successful and wide-ranging of all ground sloths.

History and A President's Find:

In 1796, Colonel John Stuart sent then Vice President-Elect Thomas Jefferson a fossil femur fragment, ulna, radius, and three massive claws. They were discovered in Greenbrier County in Virginia (now West Virginia). Thomas Jefferson examined the bones, and in 1797, in a paper he presented to the American Philosophical Society (APS) in Philadelphia, he named them "Megalonyx," meaning "giant or great claw" in Greek. However, he never gave a diagnosis as to what this animal was. He at first attributed this to a lion and even noted in the paper to APS "that he was more than three times as large as the lion." However, in the postscript of his paper, he noted a similarity to an animal recently discovered in Paraguay called Megatherium, a gigantic sloth weighing in at around 4 tons.

However, in 1799, Caspar Wistar, an American anatomist, correctly attributed the bones to a sloth, not a lion. He drew drawings of the claws in 1799. These were among the first illustrations of any vertebrate fossil in North America. Over two centuries later, these still survive in the APS in Philadelphia today. Jefferson subsequently thought this giant claw did not belong to a lion but rather an organism similar to Megatherium.

Extinction was an emerging view in natural history. However, Thomas Jefferson was a man who believed in the "completeness of nature." He thought that nature or the creator (Jefferson was a deist) would not let there be an imbalance in nature and allow a creature die off. When he became President, Jefferson had told the explorers Meriwether Lewis and William Clark to find evidence of live animals in the western United States. Of course, this made no headway, and no living specimens were discovered/described by the expedition.

In 1822, some 23 years after Wistar identified the bones, he proposed naming this species "Megalonyx jeffersonii". French anatomist Anselme Gaëtan Desmarest described it first during that same year, but Richard Harlan, an American naturalist, formally described it in 1825.

Taxonomy and Evolution:

The Megalonyx genus had a variety of species throughout its 10,000,000-year reign. Its sister species, "M.leptostomus" lived till around 250,000 years ago and was around half the size of Jefferson's Sloth. Another species, which evolved from M.leptostomus evolved into M.wheatleyi, even bigger than the preceding species. But the last, biggest, and most widespread of all was the type species, Jefferson's Ground Sloth.

Megalonyx jeffersonii is a member of the Megalonychidae family of pilosans. They're a family within the superfamily Megatheroidea which includes animals like Eremotherium, Megatherium, and Nothrotheriops (the Shasta Ground Sloth). According to recent studies, the closest modern cousins are the three-toed sloths, in fact according to molecular DNA studies both Megalonychids and three-toed sloths' family Bradypodidae are sister families within Megatheroidea.

By the end of the Pleistocene, a variety of genera would thrive across the environment. From the similarly sized Ahytherium of Brazil, and the black bear-sized Xibalbaonyx of Mexico. However, as previously stated, across Mexico, Canada, and America was Megalonyx jeffersonii.

Description:

It was fairly average size for a ground sloth. Around 10ft long and weighing in at around a ton. At the shoulder it would have stood between four and four-and-a-half feet tall. Compared to other ground sloths it had a more squared off head compared to other ground sloths, broadened peg-like teeth designed to process plant material. Its likely that the broadened skull would have enabled a broader diet in their habitat. Among the most iconic feature was the massive claws used for manipulating branches and for defense. The hind limbs ended in feet that were flattened on the side and tipped with three toes. Finally, they had a muscular tail they could have used as a prop to rear back on their hind limbs.

Habitat and Behavior:

Fossils of this species range from as far south as Southern Mexico and as far north as Yukon and into Alaska. The Jefferson's Ground Sloth was the only species of ground sloth to reach Alaska. Their numbers in the far north in regions like Yukon and Alaska were likely because they could have reached the regions during interglacial intervals of the last Ice Age. Also, this genus was the first group to reach North America so they had far more time to adapt to the regions.

As far as habitats go, these animals thrived in almost every environment that they dwelled in. Be it the scrubland of Arizona, Northern and Central Mexico, the grassland prairies of Kansas and Idaho, and the Rocky Mountain States of Utah and Colorado. However, most specimens have been found in forested coniferous environments, with Spruce Trees being the most dominant foliage in the area. Regions like La Brea in California and fossil sites in Illinois and Ohio have also been found.

In a 2013 paper, it was found that the Megalonyx genus would have had a woodland or forest-oriented browser. It would have consumed woody plants, oak trees, and other woody branches like spruce trees. Furthermore, it indicated that in parts of the American South, the sloth and various proboscideans would have browsed upon the Osage oranges, a unique fruit found in parts of Texas and Oklahoma. Nowadays, few browsing animals can consume it, so it just rots away, an example of anachronistic evolution as no browsers can consume it.

Furthermore, white-tailed deer fossils in western Iowa have been found alongside these sloths. It has been theorized that these two forest-going animals stuck together for mutual protection. However, there is no way to thoroughly verify that, as they could have just encountered each other and passed each other by in the forest.

They were filling the niche of the large browsing animal eating different plants in its habitat. Rearing up, they would have towered over most animals in their habitats. Only their giant relative, Eremotherium and proboscideans, could have been taller in their environments.

By studying the only terrestrial pilosan alive today, the giant anteater, it could be extrapolated that these giant sloths carried their babies on their backs until they were old enough to walk alongside their mothers. Their massive torsos would have made for an excellent spot to rest and stay safe from any potential predators.

Fossils found in Iowa have shown evidence of parental care and even extended social behavior in these sloths. An adult individual was found in direct association with two smaller individuals with paleontologists theorizing that varying generations caring for their young.

As far as ground sloths go, these were large, but they may not have been entirely untouchable. Predators like the American Lions, Smilodon (saber-toothed cats), and packs of Dire Wolves could have hunted and killed these animals, especially since it is believed some of these predators hunted in packs. Also, Short-Faced Bears could have preyed upon these sloths occasionally, too.

However, above all, there was one animal that could've easily hunted them and hunted them to a degree that would mean the end of these awe-inspiring animals.

Extinction:

These sloths along with countless other megafauna would vanish around 10-11,000 years ago. Why they went extinct is largely believed to have been due to both climate change and human hunting. A fossil femur of a Jefferson's Ground Sloth found near Snowmount Village (near Aspen) in Colorado has shown evidence of human butchery dated to around 13,000 years ago. In Ohio, a nearly complete specimen was found with evidence of butchery as well.

Ground sloths would persist in the Caribbean for the next few thousand years with Megalocnidae in Hispanola, Puerto Rico and Cuba, but by ~1600-1550 BCE, none would be left on the planet.

Despite the fact that this sloth had gone extinct some 11,000 years ago, its mark on paleontology and history is undeniable. Thomas Jefferson's description of this animal is largely credited as being the beginning of American Paleontology. And the find was not a dinosaur or a marine reptile, but a sloth.
___________________________________________________________________________________________
One of the most iconic sloths found in North America and I feel it needed to be redone again.

It was made by LazardiK and his Sloth pack as I said in the previous profile.

I modified the skull some more and gave it a baby model as well. Plus it was made before I got a handle on the sloth rig so it needed to be reposed rig-wise as well.

As I said before, this guy does great Paleoart:
Ground Sloths 2 - Megalonychids by artbyjrc on DeviantArt

FYI: The paper where I referenced the white-tailed deer was here:
A Ground Sloth, Megalonyx, from a Pleistocene Site in Darke Co., Ohio (core.ac.uk)

I also wanted to depict white-tails alongside them too so I added them to the profile and made it two mothers with their babies.

Will this be used in Past Meets Present? Ahhhh... now I'm not so sure...

There will be ground sloths in season 2, but I've got quite a few already in the episode featuring ground sloths and I really don't want to oversaturate the episode with sloths as cool as they are. I'd say 40% no as I've already got a good candidate to fill a similar niche.

I am working on some more profiles, but work and PMP has kind of slowed me down.

Original model and skin by LazardiK :
Jefferson's Ground Sloth (Lazardi) | ZT2 Download Library Wiki | Fandom

White-Tailed Deer by ZTABC:
White-tailed Deer (ZTABC Team) | ZT2 Download Library Wiki | Fandom

For Past Meets Present:
Past Meets Present - Page 5 - The ZT2 Round Table