Schizotheriines are one of the two subfamilies of the extinct

family Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Chalicotheriidae Chalicotheres (from Greek '' chalix'', "gravel" and '' therion'', "beast") are an extinct clade of herbivorous, odd-toed ungulate (perissodactyl) mammals that lived in North America, Eurasia, and Africa from the Middle Eocene until the Early Pl ...

, a group of

herbivorous A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthpart ...

odd-toed ungulate Odd-toed ungulates, mammals which constitute the taxonomic order Perissodactyla (, ), are animals—ungulates—who have reduced the weight-bearing toes to three (rhinoceroses and tapirs, with tapirs still using four toes on the front legs) ...

(perissodactyl)

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

s that lived from the Eocene to the Pleistoscene. The other clade is the

Chalicotheriinae Chalicotheriines are one of the two subfamilies of the extinct family Chalicotheriidae, a group of herbivorous, odd-toed ungulate ''(perissodactyl)'' mammals that lived from the Eocene to the Pleistocene. The other subfamily is the Schizotherii ...

. Both clades had claws rather than hooves on their front feet, an adaptation understood as related to feeding. Schizotheriines also had claws on their hind feet. The fossils of both groups are found in environments that had trees and shrubs. While chalicotheriines developed very derived body forms, schizotheriines remained basically similar in shape to other perissodactyls such as horses and tapirs. Like most forest-dwelling ungulates, they had long necks and forelimbs longer than their hindlimbs. Schizotheriines had longer, higher-crowned cheek teeth than chalicotheriines, which indicates they typically fed on tougher vegetation. The sediments where their fossils are found show they also lived in a wider range of environments, from moist forests to drier woodland or savannah-like environments with trees. Perhaps for this reason, they became more widely distributed than chalicotheriines. Though chalicotheres likely evolved in Asia, schizotheriine fossils are also found in Africa and North America, which they reached by the Bering land bridge. The best-known schizotheriine genus is ''

Moropus ''Moropus'' (meaning "slow foot") is an extinct genus of large perissodactyl ("odd-toed" ungulate) mammal in the chalicothere family. They were endemic to North America during the Miocene from ~20.4—13.6 Mya, existing for approximately ...

''. The last survivor of the group was traditionally thought to be '' Nestoritherium'', but it was found to actually be a member of Chalicotheriinae. Analysis of

dental microwear Dental microwear analysis is a method to infer diet and behavior in extinct animals, especially in fossil specimens. Typically, the patterns of pits and scratches on the occlusal or buccal surface of the enamel are compared with patterns observed ...

implies that most Miocene Schizotheriinae fed on leaves, fruit, bark and twigs. Their claws were likely used in a hook-like manner to pull down branches to bring these items within reach of the mouth, suggesting they lived as high

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. Some paleontologists have suggested other uses for the claws, such as stripping bark from trees. Though the claws on the forefeet were long, they could be retracted, so the animals could walk normally on the sole of the foot. The claw-retraction mechanism was unique to schizotheriines, and different from the structure in cats. The broad base of the hind legs may have allowed schizotheriines to rear upright and brace themselves against a tree trunk in order to reach higher for food.

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Further reading