Chalicotheriidae

Chalicotheriidae(fromGreekchalix,"gravel" andtherion,"beast" ) is an extinctfamilyofherbivorous,odd-toed ungulate(perissodactyl)mammalsthat lived inNorth America,Eurasia,andAfricafrom theMiddle Eoceneto theEarly Pleistocene.They are often calledchalicotheres,a term which is also applied to the broader grouping ofChalicotherioidea.They are noted for their unusual morphology compared to other ungulates, such as their clawed forelimbs. Members of the subfamilyChalicotheriinaedeveloped elongate gorilla-like forelimbs that are thought to have been used to grasp vegetation.They are thought to have beenbrowserson foliage as well as possibly bark and fruit.

Chalicotheriidae Temporal range: middleEoceneto earlyPleistocene~
Moropus elatus(Schizotheriinae) at the National Museum of Natural History, Washington, DC
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Perissodactyla
Superfamily:	†Chalicotherioidea
Family:	†Chalicotheriidae Gill,1872
Type genus
†Chalicotherium Kaup,1833
Subfamilies
†ChalicotheriinaeGill, 1872 †SchizotheriinaeHollandand Peterson, 1914

History of discovery

The earliest remains chalicotheres were discovered wereungualphalangesfound nearEppelsheim,Germany in early 19th century. These remains were considered to belong to giganticpangolinsbyGeorges Cuvierin 1822 whileJohann Jakob Kaupin 1833 alternatively attributed them todeinotheres.Also in 1833, Kaup described chalicothere teeth as belonging to the new genusChalicotheriumfrom the same locality, which he did not recognise as belonging to the same species as the ungual phalanges. Beginning in the 1930s, theSansan depositin southern France was excavated for fossils, yielding remains of chalicotheres. In 1837, postcranial remains from the deposit were given the name "Macrotherium "byÉdouard Lartet,who like Cuvier thought the remains represented those of a giant pangolin/edentate.In 1849,Henri Marie Ducrotay de Blainvilledescribed chalicothere skull remains from Sansan as belonging to the ungulate genusAnoplotherium(an extinct even-toed ungulate now known to be unrelated to chalicotheres). It was only in 1890 that a complete chalicothere skeleton found at Sansan was described byHenri Filhol,showing the skulls/teeth and the postcranial remains belonged to the same unusual animal.

Description

Life restoration of the chalicotheriineAnisodon grande,formerlyChalicotheriumgrande.

Unlike modern perissodactyls, chalicotheres had clawed feet. They had, lower incisors that cropped food against a toothless pad in the upper jaw, low-crowned molar teeth, and werebrowserson trees and shrubs throughout their history. They evolved in two different directions, which became separate subfamilies, theSchizotheriinaeand theChalicotheriinae.

Schizotherine chalicotheres such asMoropushad relatively equal length limbs,and 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 ofgiraffes.Strong hindlimbs and an elongated pelvis suggest they could have reared upright as moderngoatsdo, 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 asAnisodon,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 livinggeladamonkey. 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.They could not retract the huge front claws, and knuckle-walked on their forelimbs. The chalicotheriines' anatomical design, posture, and locomotion showconvergencewith other large browsers that feed selectively in a bipedal position, such as theground sloths,gorillas,andgiant pandas.

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 schizotheriineMoropusfrom the early Miocene of North America, and the chalicotheriineAnisodonfrom 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.

Evolution

Chalicotheres are part of the orderPerissodactyla,which includes modernequines,rhinoceroses,andtapirs,as well as extinct relatives likebrontotheres.As the early evolution of perissodactyls is still unresolved, their closest relatives among other perissodactyl groups is obscure.They are generally placed as part of the cladeAncylopodaalongside their close relativesLophiodontidae.Many studies considered them as closer toCeratomorpha(which includes tapirs and rhinoceroses) than Equoidea.A 2004cladisticstudy alternatively recovered Ancylopoda as sister to all modernperissodactyls(which includes Equoidea and Ceratomorpha), with thebrontotheresas the most distantly related within the orderPerissodactyla.

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 lateOligocene,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.)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.

Never common animals, the chalicotheres declined from the lateNeogeneonwards, disappearing from North America and Europe by end of theMiocene.The youngest chalicotheres are the chalicotheriinesHesperotheriumfrom theEarly Pleistoceneof China,Nestoritheriumfrom the Early Pleistocene of Myanmar,as well as the schizotheriineAncylotheriumfrom the Early Pleistocene of Eastern and Southern Africa,also possibly known from the Early Pleistocene of China.