Chalicotheriidae

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Chalicotheriidae
Temporal range: middle Eocene to early Pleistocene ~48.6–1.806  Ma
Moropus.jpg
Moropus elatus at the
National Museum of Natural History,
Washington, DC
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Perissodactyla
Superfamily: Chalicotherioidea
Family: Chalicotheriidae
Gill, 1872 [2]
Type genus
Chalicotherium
Kaup, 1833
Subfamilies

Chalicotheriinae Gill, 1872
Schizotheriinae Holland and Peterson, 1914 [3]

Contents

Chalicotheriidae (from Greek chalix , "gravel" and therion , "beast") is an extinct family of herbivorous, odd-toed ungulate (perissodactyl) mammals that lived in North America, Eurasia, and Africa from the Middle Eocene until the Early Pleistocene, existing from 48.6 to 1.806 mya. They are often called chalicotheres, a term which is also applied to the broader grouping of Chalicotherioidea. [4] They are noted for their unusual morphology compared to other ungulates, such as their elongated clawed forelimbs. [5] They are thought to have been browsers. [4]

Description

Anisodon grande, formerly Chalicotherium grande. ChalicotheriumDB1.jpg
Anisodon grande , formerly Chalicotherium grande.

Unlike modern perissodactyls, chalicotheres had clawed feet. They had longer forelimbs and shorter hind limbs, lower incisors that cropped food against a toothless pad in the upper jaw, low-crowned molar teeth, and were browsers on trees and shrubs throughout their history. They evolved in two different directions, which became separate subfamilies, the Schizotheriinae and the Chalicotheriinae.

Schizotherine chalicotheres such as Moropus lived in a variety of forest, woodland, and savannah habitats in Asia, Africa, and North America. They developed long necks and skull adaptations that suggest they had long, extensible tongues to reach browse, like those of giraffes. Strong hindlimbs and an elongated pelvis suggest they could have reared upright as modern goats do, and used their front claws to pull branches within reach of the tongue. The claws were retractable, and they walked normally on the bottom of the foot. Studies of tooth wear suggest they ate leaves, twigs, fruit, and bark.

Chalicotheriines, such as Anisodon, lived only in moist, closed-canopy forests, never reached the Americas, and developed very unusual anatomy for an ungulate. Their shorter necks and horse-like heads did not show adaptations to reach high. Instead, they developed very long forelimbs with mobile shoulder joints and hooklike claws. The pelvis and hindlimbs were specialized to stand upright, and to sit for hours while feeding, like the living gelada monkey. Some early paleontologists thought the claws were used to dig up roots and tubers, but their teeth were designed for soft foods, and studies of tooth wear show they ate fruit and seeds. Their forelimbs were specialized to reach, grasp, and strip or sweep plants to the mouth. [6] They could not retract the huge front claws, and knuckle-walked on their forelimbs. The chalicotheriines' anatomical design, posture, and locomotion show convergence with other large browsers that feed selectively in a bipedal position, such as the ground sloths, gorillas, and giant pandas. [7]

Chalicothere fossils are uncommon even in areas where other taxa of similar size are well-preserved, which suggests they were mostly solitary animals, and unlike horses, rhinos, and brontotheres, never evolved species that lived in herds. Only two species of chalicothere are known from complete skeletons, the schizotheriine Moropus from the early Miocene of North America, and the chalicotheriine Anisodon from the middle Miocene of Europe. Fossils of other species range from very fragmentary to moderately complete. Chalicotheres ranged in size from an antelope to a large draft horse. [8]

Evolution

Chalicotheres can be first identified with certainty around 46 million years ago, in the Eocene of Asia. The family is thought to have evolved there, but appeared in North America by the Eocene. By the late Oligocene, they had divided into schizotheriines and chalicotheriines. (Earlier chalicotheres are often referred to the family Eomoropidae; it is not yet clear whether they had claws or how the two subfamilies diverged.) [8] Both subfamilies were successful over many millions of years, and reached their greatest diversity in the Miocene. Advanced schizotheriines (Moropus) entered North America via the Bering land bridge at the Oligicene-Miocene boundary, and expanded southward into Central America. [9] There were multiple radiations into Africa, where chalcotheriines were later replaced by schizotheriines. Both groups spread early into Europe. In the Pliocene, they would have faced new competition in North America from megalonychid ground sloths which emigrated from South America in the Great American Interchange, and from evolving great apes in African and European forests. The family became less successful after the Miocene but persisted in Africa until the end of the Pleistocene; the latest surviving species was the schizotheriine Ancylotherium hennigi. [8] [10]

Chalicotheres are related to the extinct brontotheres, as well as to modern day horses, rhinoceroses, and tapirs. [11] As the early evolution of perissodactyls is still unresolved, their closest relatives among other perissodactyl groups is obscure. [12] They have been traditionally ranked as closer to Ceratomorpha (which includes tapirs and rhinoceroses) than Equoidea. [13] However, a 2004 cladistic study recovers chalicotheres as the sister group to Lophiodontidae, and the combined group (Ancylopoda) as sister to all modern perissodactyls (which includes Equoidea and Ceratomorpha), with the brontotheres as the most distantly related within the order Perissodactyla. [14]

Related Research Articles

<span class="mw-page-title-main">Ancylopoda</span> Extinct suborder of mammals

Ancylopoda is a group of browsing, herbivorous, mammals in the Perissodactyla that show long, curved and cleft claws. Morphological evidence indicates the Ancylopoda diverged from the tapirs, rhinoceroses and horses (Euperissodactyla) after the Brontotheria; however, earlier authorities such as Osborn sometimes considered the Ancylopoda to be outside Perissodactyla or, as was popular more recently, to be related to Brontotheriidae.

<span class="mw-page-title-main">Perissodactyla</span> Order of hoofed mammals

Perissodactyla is an order of ungulates. The order includes about 17 living species divided into three families: Equidae, Rhinocerotidae (rhinoceroses), and Tapiridae (tapirs). They typically have reduced the weight-bearing toes to three or one of the five original toes, though tapirs retain four toes on their front feet. The nonweight-bearing toes are either present, absent, vestigial, or positioned posteriorly. By contrast, artiodactyls bear most of their weight equally on four or two of the five toes: their third and fourth toes. Another difference between the two is that perissodactyls digest plant cellulose in their intestines, rather than in one or more stomach chambers as artiodactyls, with the exception of Suina, do.

<i>Moropus</i> Extinct genus of mammals

Moropus is an extinct genus of large perissodactyl mammal in the chalicothere family. They were endemic to North America during the Miocene from ~20.4–13.6 Mya, existing for approximately 6.8 million years. Moropus belonged to the schizotheriine subfamily of chalicotheres, and has the best fossil record of any member of this group; numbers of individuals, including complete skeletons, have been found.

<span class="mw-page-title-main">Notoungulata</span> Extinct order of hoofed mammals

Notoungulata is an extinct order of ungulates that inhabited South America from the early Paleocene to the end of the Pleistocene, living from approximately 61 million to 11,000 years ago. Notoungulates were morphologically diverse, with forms resembling animals as disparate as rabbits and rhinoceroses. Notoungulata are the largest group of South American native ungulates, with over 150 genera in 14 families having been described, divided into two major subgroupings, Typotheria and Toxodontia. Notoungulates first diversified during the Eocene. Their diversity declined from the late Neogene onwards, with only the large toxodontids persisting until the end of the Pleistocene, perishing as part of the Late Pleistocene megafauna extinctions along with most other large mammals across the Americas. Collagen sequence analysis suggests that notoungulates are closely related to litopterns, another group of South American ungulates, and their closest living relatives being perissodactyls, including rhinoceroses, tapirs and equines as part of the clade Panperissodactyla. However their relationships to other South American ungulates are uncertain. Several groups of notoungulates separately evolved ever-growing cheek teeth.

<i>Miacis</i> Extinct genus of carnivores

Miacis is an extinct genus of placental mammals from clade Carnivoraformes, that lived in North America from the early to middle Eocene.

<i>Chalicotherium</i> Extinct genus of mammals

Chalicotherium is a genus of extinct odd-toed ungulates of the order Perissodactyla and family Chalicotheriidae. The genus is known from Europe and Asia, from the Middle Miocene to Late Miocene.

<i>Ancylotherium</i> Extinct genus of mammals

Ancylotherium is an extinct genus of the family Chalicotheriidae, subfamily Schizotheriinae, endemic to Europe, Asia, and Africa during the Late Miocene-Early Pleistocene, existing for approximately 9.8 million years.

<span class="mw-page-title-main">John Day Formation</span>

The John Day Formation is a series of rock strata exposed in the Picture Gorge district of the John Day River basin and elsewhere in north-central Oregon in the United States. The Picture Gorge exposure lies east of the Blue Mountain uplift, which cuts southwest–northeast through the Horse Heaven mining district northeast of Madras. Aside from the Picture Gorge district, which defines the type, the formation is visible on the surface in two other areas: another exposure is in the Warm Springs district west of the uplift, between it and the Cascade Range, and the third is along the south side of the Ochoco Mountains. All three exposures, consisting mainly of tuffaceous sediments and pyroclastic rock rich in silica, lie unconformably between the older rocks of the Clarno Formation below and Columbia River basalts above.

<span class="mw-page-title-main">Palaeotheriidae</span> Extinct family of mammals

Palaeotheriidae is an extinct family of herbivorous perissodactyl mammals that inhabited Europe, with less abundant remains also known from Asia, from the mid-Eocene to the early Oligocene. They are classified in Equoidea, along with the living family Equidae.

<i>Tylocephalonyx</i> Extinct genus of chalicothere

Tylocephalonyx is an extinct chalicothere from the Miocene of North America.

<i>Borissiakia</i> Extinct genus of herbivorous odd-toed ungulates

Borissiakia is an extinct genus of chalicothere, a group of herbivorous, odd-toed ungulate (perissodactyl) mammals, that lived during the late Oligocene in Kazakhstan. They had claws that were likely used in a hook-like manner to pull down branches, suggesting they lived as bipedal browsers.

Chemositia is an extinct genus of chalicothere, a group of herbivorous, odd-toed ungulate (perissodactyl) mammals. They lived in Africa, and had claws that were likely used in a hook-like manner to pull down branches, suggesting they lived as bipedal browsers.

<span class="mw-page-title-main">Schizotheriinae</span> Extinct subfamily of mammals

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

Metaschizotherium is an extinct genus that belongs to the family Chalicotheriidae, which was a group of herbivorous perissodactyl ("odd-toed") mammals. Though found primarily in Europe, fragmentary remains suggest that their range extended into Asia.

<span class="mw-page-title-main">Chalicotheriinae</span> Extinct subfamily of mammals

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 Schizotheriinae. Chalcotheriines evolved unique characteristics for ungulates, with very long forelimbs, short hindlimbs, and a relatively gorilla-like physique, including knuckle-walking on their flexible forelimbs, which bore long curved claws. Members of this subfamily possessed some of the longest forelimbs and shortest hindlimbs in relation to each other out of all extinct animals. Analysis of dental wear implies that most chalicotheriines fed on seeds and fruit. Their claws were likely used in a hook-like manner to pull down branches, suggesting they lived as bipedal browsers.

<span class="mw-page-title-main">Phenacodontidae</span> Family of mammals

Phenacodontidae is an extinct family of large herbivorous mammals traditionally placed in the “wastebasket taxon” Condylarthra, which may instead represent early-stage perissodactyls. They lived from the late early Paleocene to early middle Eocene and their fossil remains have been found in North America and Europe. The only unequivocal Asian phenacodontid is Lophocion asiaticus.

<span class="mw-page-title-main">Brontotheriidae</span> Extinct family of odd-toed ungulates

Brontotheriidae is a family of extinct mammals belonging to the order Perissodactyla, the order that includes horses, rhinoceroses, and tapirs. Superficially, they looked rather like rhinos with some developing bony nose horns, and were some of the earliest mammals to have evolved large body sizes. They lived around 56–34 million years ago, until the very close of the Eocene. Brontotheres had a Holarctic distribution, with the exception of Western Europe: they occupied North America, Asia, and Eastern Europe. They were the first fossilized mammals to be discovered west of the Mississippi, and were first discovered in South Dakota.

The Astoria Formation is a geologic formation in Washington state & Oregon. It preserves fossils dating back to the early to middle Miocene.

Isectolophidae is an extinct family of browsing, herbivorous, mammals in the order Perissodactyla. It forms a sister group to the rest of the Tapiromorpha, which includes the Ancylopoda and the Ceratomorpha.

Nanotitanops is an extinct genus of Brontothere from the middle Eocene of China. It contains a single species, N. shanghuangensis. It is known only from isolated teeth, the smallest of any known Brontothere.

References

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