Moropus elatus

The "foolish foot"

Click here to see the skeleton of Moropus

Click here to see the restored musculature of Moropus

It was many years after the first Moropus bones were discovered when paleontologists finally figured out that the huge claws on the feet actually belonged to this animal. They had assumed these massive claws were from a giant sloth. But when more Moropus discoveries were subsequently made at Agate Springs with the claws articulated with the skeleton, and the skull intact, that the unlikely truth was revealed.

Moropus lived during the early Miocene epoch. It belonged to an ancient  herbivore group called the Chalicotheres, which were Perissodactyl (odd-toed) mammals. This group includes rhinos, horses and tapirs. It was a contemporary of Daeodon and one can imagine some tense encounters at the waterhole between these two powerful beasts. Otherwise  it is likely they avoided each other when ever possible. 

 Because of the increasingly  arid climate, grassland environments were spreading across  western North American during the Miocene epoch. The explosive radiation of grazing Artiodactyl (even-toed) species soon followed. But as the skeletal adaptations of Moropus will show, there were sufficient tree and shrub environments such as savannah or riparian (along water ways) zones for this specialized animal to live on.

The skeleton of Moropus is very robust. The living adult animal stood eight  feet at the shoulder. The limb proportions of Moropus are giraffe-like in that the forelimbs are substantially longer than the rear. The skull is deep and superficially resembles a horse. The molars were broad and low crowned indicating that Moropus was a browser, preferring to feed on softer, leafier material rather than on grass which contains a lot of the tough mineral silica in its tissues. This requires a tooth with a high, sharp, and deeply folded enamel crown to break it down, such as that found in horses. The current belief is that Moropus was able to stand on its powerfully stout hind limbs and pull tree branches towards its mouth with the long clawed front legs. There were no horns or antlers of any kind which could have interfered with  feeding on thick trees and shrubs. It is possible that Moropus could have had a prehensile tongue or lips, as many Artiodactyl and Perissodactyl  animals do today, which aid in the efficient gathering of food. The cervical (neck) vertebrae of Moropus had an oblique ball and socket articulation at the centrums which allowed Moropus to hold its head exceptionally high. But it is plainly clear that the head could easily reach the ground just as well, where it would occasionally eat some grass, not to mention drink.

The three  highly compressed claw-like hooves on each foot were split down the middle.  These claws actually gave Moropus its name: " slow "or "sloth foot". This name implies that because of the claws, Moropus was a clumsy mover. But the articulation of the phalangeal (finger) bones, in addition to probable large foot and toe pads, shows that Moropus probably could raise the claws slightly to enable it to move about quite smoothly. Because the hooves curve inward, it probably had a pigeon-toed gait.

The Chalicothere family had a long and successful evolutionary history spanning 25 million years. Their fossilized remains are found in North America, Europe, Asia and Africa. Asia is where  Moropus is believed to have immigrated from before becoming a permanent American resident. Chalicotheres are not very numerous fossils, indicating that they probably did not live in large congregations. But these perrisodactyls are well represented throughout the different faunas that they are known from around the world.  Chalicotheres survived in the old world tropics until the last ice age 12,000 years ago.