Tag Archives: pliocene

Jeffersons sloth, megalonyx or (greek) “giant claw” is an extinct genus of ground sloths of the family megalonychidae.

Aside from there deceivingly large cuddly, and playful looks. These critters were native and unique to north America during the pliocene and pleistocene. However, because of not many remains, we don’t know as much as some of the other late pleistocene vertabrates. Like sabretooth tiger or direwolf, who were probably found in areas better suited to decomposition.

Thomas Jefferson recorded fossil bones from this animal that had been recovered from a mining cave in West Virginia in the late eighteenth century. Originally, Jefferson thought the remains belonged to a giant cat, based on the size of the large claws. Soon he realized however, that the animal was closely related to South American tree sloths. In 1797, he presented the scientific paper about his findings on megalonyx, or ‘large claw’ to the American philosophical society. The subject was the first two scientific articles ever published in the North America on fossils. Marking the continental beginning of vertebrate paleontology.

Biology and physical description:
There size was quite large. Bigger than most grizzlys, and flat nosed bears. 4m or 10 feet high. Up to 1000Kg or 2200lb big. They had a blunt snout and massive jaw. Large peg like teeth. There hind limbs were flat footed. And, a stout tail. Its believed this allowed them a rear up semi errect portion to feed on leaves.
Forelimbs had 3 highly developed claws. They were quite long. Up to 15-20 inches. Used to strip trees and tear off branches. (the deceiving part)
As with other sloths, the teeth had an outer layer of dentine, rather than enamel, and thus were softer than those of other mammals. Soft teeth wear faster than hard teeth, and to compensate for this, their teeth continued to grow throughout their lifetime (MacFadden et al. 2010).
Although very few specimens have been recovered with preserved soft tissue, better preserved species of late pleistocene ground sloths (shasta ground sloth) were found. And, it is thought that Jefferson’s ground sloth was similarly covered with thick hair.
Sloth bones are truly strange inside and out. Inside, they are virtually unique in the animal kingdom in the absence of any marrow cavity within their long bones. Instead of marrow, the bones are filled with a honeycomb network of bony struts and braces called trabecular or cancellous bone. This gave the bones great strength without the cost of extra weight. Whether that was necessary because of sloths’ weight, due to a unusually active life-style or just an accident of evolution is unknown.

Habitat: woodlands and forest:
Jefferson’s ground sloth had the widest range of all North American ground sloths. They have been recovered from over 150 sites across the United States, as well as from northwestern Canada and western Mexico (Hoganson and McDonald 2007; McDonald et al. 2000). Furthermore, they are the only ground sloth that has been recovered from the Yukon and Northwest Territories in Canada.
Two recent studies were able to link directly-dated specimens from the terminal pleistocene with regional paleoenvironmental records, demonstrating that these particular animals were associated with spruce dominated, mixed conifer-hardwood habitats. (Hoganson and McDonald 2007; Schubert et al. 2004).
Scarcity in the Great Plains has been noted and interpreted as reflecting the paucity or absence of forested areas, the species’ preferred habitat, within the region. (Hoganson and McDonald 2007).

Habitat: Caves:
Megalonyx jeffersoni remains have been recovered from late Pleistocene sites, primarily caves, across the Midwest. These sites include West Cave and Brynjulfson Cave #1 in central Missouri, a site in the Galena Lead region of northwestern Illinois, the Hanson Megalonyx from Minneapolis, Minnesota, the Carter site in western Ohio, Gillenwater near Bowling Green, Kentucky, Robinson Cave in northeastern Tennessee, and Cheek Bend Cave and Darks Mill in central Tennessee.
It is likely several types of habitats were utilized by jefferson’s ground sloth over the course of the Pleistocene.

Evolution:
The first wave of megalonychidae came to North America by island-hopping across the Central American Seaway from South America, where ground sloths arose, prior to formation of the Panamanian land bridge. Based on molecular results, its closest living relatives are the three-toed sloths (Bradypus).

Behaviour:
It probably lived solitarily, only getting together for seasonal mating.
While most ground sloths walked on the outsides of their hind feet, Jefferson’s ground sloth kept their feet flat while walking. Furthermore, the shape of the hip bone indicates that this animal could also stand on its hind legs, using its stout tail for support.
During excavations at Tarkio Valley in southwest Iowa, an adult Megalonyx was found in direct association with two juveniles of different ages, suggesting that adults cared for young of different generations.

Diet:
Teeth shape suggest they were a browser who primarily ate leaves, twigs and possibly nuts. (Kurten and Anderson 1980; McDonald 2005). Isotopic results are consistent with this. (Kohn et al. 2005). Analysis of the bone chemistry of indicate the animal had an herbivorous diet, (France et al. 2007), which is in keeping with a previous study conducted for ‘giant claw’ recovered in Alberta, (Bocherens et al. 1994).

Extinction: The youngest widely-accepted radiocarbon dates are from northern Illinois. Obtained from purified bone collagen. A combined age date of 13,800-13,160 years ago.
(Schubert et al. 2004). A slightly older direct date of 13,830-13,560 cal BP was obtained on a toe bone (ungual) in North Dakota (Hoganson and McDonald 2007).

Bipedal Walking:
How and why humans separated themselves from the other primates and began striding confidently on two legs is a question mankind has asked for thousands of years. Many scientists consider it the single characteristic that put us on the evolutionary path to becoming tool-users and uniquely human. So it was with no little surprise that scientists realized 100 years ago that some ground sloths probably could walk upright also. Why do they do it? What advantage is there that all the rest of the mammals have overlooked? Perhaps the answer can be found by considering the theories of why our human ancestors did.
Some scientists credit changing climate, and expanding savannas offering rich new ecological niches to a species that could climb down and out of the trees. Moving more efficiently and safely to open ground. Standing erect may have also been necessary to see predators approaching.
-Other scientists suggest foraging from the ground and being forced to reach up into the trees for food encouraged our ancestors to remain upright to reduce the effort of repeatedly lifting and lowering their torsos; and,
-Some scientists suggest the benefit of being able to hold things in their hands or arms was the force that put us on the bipedal evolutionary path. They also cite tools, food collection and/or infants needing an extended period of maternal care as the motivating force(s).
No one thinks sloths are as efficient striders as humans became. Then again, no one believes primate ancestors dropped out of trees and started walking. What did you think?
Whatever benefits ancestors reaped from upright standing. It started a long time ago, and improved from there. Studying megalonyx may some day produce new insights into our own evolution. Maybe they wanted to have a better view of the moon and solar system. One things for sure, the world is not the same without megalonyx, jeffersons ground sloth or ‘giant claws.’

North American scimitar – homotherium serum

Following its favorite snack, the woolly mammoth, it was said north American scimitar toothed cats may have migrated across the bering land bridge and spread throughout north America.

Discovery was by the famous French paleontologist Baron Cuvier, in 1824. He was the first to describe the serrated teeth of homotherium from deposits in France, thinking they belonged to a bear, or something else. They had less fossils than there cousins the sabre tooth cats, and it was believed they originated from them somehow, or, other cat beasts millions of years ago. Emilio Fabrini proposed the name homotherium in 1890. Translated in greek as ‘same beast’.

In north American, around 1893, the scimitar cat was first described by E.D. Cope as dinobastis serus. Its remains, from deposits dating between about 1.5 million and 10,000 years old, are known from Yukon to Florida. By 1962, they had adopted homotherium serum.

There is little doubt the “same beasts, or scimitars”, like sabre tooth cats, were derived from the late pliocene – early pleistocene (about 2 million years). And in turn, derived from machairodus, even longer ago.

Biology: 6 feet and 300 pounds?
Modern lions are similar size to scimitar but without the slender limbs. “same beasts” had 4 inch wide serrated teeth to inflict wounds. And, unlike there sabre tooth cousins teeth, which may have been a sexual attraction in finding mates, there shorter wider, finely serrated teeth, made a more powerful slicing tool. They had long legs, and sloping back. It allowed scimitar to travel up to 65km/h. See enlarged nose and nostrils? These cats were sneaky, sensory killing machines.

Actual skeletons of ‘same beasts’ suggests that h. serum is built for short bursts of speed, as well as agility. The first neck of the vertebra helped to support there massive muscles used to depress the head and teeth to inflict a killing bite. The pelvic region, including the sacral vertebrae, are bear-like. As is the short tail composed of 13 vertebrae. About half the number in long-tailed cats. Such features suggest ambushing and coming from behind.

Gassaway fissure and Friesenhahn caves:

The recovery adults and there cubs from caves in Texas and Tennessee suggest these animals lived in dens, possibly in family groups. This is further supported by the association of multiple mastodons found inside them. And, unlike dens of some of the other cat like species like sabretooths, mountain lions and others.

Did u see a scimitar cave den?

A partly dis-articulated skeleton of a juvenile, found with two complete adult skeletons, from Gassaway Fissure, Tennessee, estimated to have been 2 to 4 months old at death, probably represents a cub born in a denning cave.

Of great interest, were between 300 and 400 juvenile mammoths found in the caves. The majority were just 2-year olds. probably such calves became easy prey for scimitar cats. Indeed, the association of scimitars, homotherium or “same beasts” with proboscideans (elephants and mastodons) and rhino remains constant. It reinforces the idea that ‘same beasts or scimitars’ preyed selectively on these tough-skinned animals. As well long nose peccary’s, and turtles which were found in Texas, these “same beasts” would probably take down anything smaller than a young mastodon or rhino. Given the meal size, it could last there family weeks, or more.

What is a scimitar hunt?

Picture a grassy parkland like environment where mammoth or prey are usually found.    Leaving its cave shelter or den, from stalking, the felid cat beast approaches a small heard of mammoths.    After crouching behind small juniper tree brushes, it selectively finds its prey. A young 2 year old columbian mammoth playing slowly at distance from the pack. So starts a blindsidingly quick rush alongside the mammoth calf (pic). The cat jump attacks, snowballing its prey over, its deep claws pierce the shoulder of the mammoth so bad it is screaming.   Straddling the chest of the crying woolly calf, the beast cat slashes the exposed mammoths neck with its scimitars. Immediately the child mammoths mother, and rest of the herd move forward, trumpeting towards action. Within minutes the mammoth calf quickly bleeds to death, while the ‘cat beast” retreats to cover nearby.    When the herd finally abandons the young mammoth kill, the cat cautiously approaches, dragging the body in its powerful jaws, into its cave.  There it dismembers and eats its prey, shearing and breaking down large chunks of flesh with its fangs and gulping them down.    Only its baby teeth and its limb bone sockets are left, with telltale scratches and marks left to commemorate the scimitar cats killing power.