Chalicotheriidae

The history of chalicothere research began in the early nineteenth century with the discovery of ungual phalanges near Eppelsheim in Germany. In 1822, Georges Cuvier interpreted these unusual claw bones as belonging to a gigantic pangolin. Johann Jakob Kaup later described chalicothere teeth from the same locality as the new genus Chalicotherium in 1833, but did not recognise that the teeth and claws belonged to the same kind of animal. The Miocene locality of Sansan in southern France played a central role in clarifying the nature of chalicotheres. Fossils from Sansan included postcranial remains named Macrotherium by Édouard Lartet in 1837 and cranial remains later referred by de Blainville to Anoplotherium in the 1840s. It was only after the discovery and description of a more complete skeleton by Henri Filhol in 1890 that the skull, teeth and unusual limb bones were firmly recognised as belonging to the same animal. == Description and functional morphology ==

, formerly Chalicotherium grande''. Chalicotheriids were unusual among Perissodactyla in possessing large claws rather than hooves. Despite this, their dentition was that of browsing herbivores: the cheek teeth were low-crowned, and the lower incisors cropped vegetation against a toothless pad in the upper jaw. Chalicotheriids ranged in size from small antelope-sized forms to animals comparable to large draft horses. The family is generally divided into two subfamilies, Chalicotheriinae and Schizotheriinae, which differ in the skull, teeth, and appendicular skeleton. Skull and dentition The skull and lower jaw differed noticeably between the two subfamilies. Schizotheriines generally had more slender mandibles, a tapered anterior horizontal ramus, and a relatively low symphysis, whereas chalicotheriines tended to have more robust jaws and, in at least some species, a longer diastema and a fuller complement of lower anterior teeth. New mandibular material of Chalicotherium brevirostris showed that this species had a long snout, a long diastema, and three lower incisors plus a canine, revising earlier assumptions based on more fragmentary material. Forelimbs, claws, and stance The forelimbs were the most distinctive part of chalicothere anatomy. Coombs interpreted chalicotheres as a perissodactyl lineage specialised for browsing on higher vegetation, with the hook-like manual digits used to pull branches within reach of the mouth rather than primarily for digging. Schizotheriines retained more even limb proportions and were probably more typical quadrupedal browsers, although they also show adaptations consistent with rearing and branch-pulling. In derived schizotheriines, the proximal and middle phalanges of the second manual digit fused to form the distinctive duplex bone. This fusion immobilised the joint and is one of the clearest specialisations of the schizotheriine manus. Chalicotheriines were more specialised in the forelimb, with proportionally longer forelimbs and a more unusual manus. A knuckle-supported forelimb stance has often been reconstructed for forms such as Chalicotherium, but this should be treated as an interpretation rather than an absolutely settled fact. Recent work has suggested that both chalicothere subfamilies evolved ways of limiting movement in the digits, but that schizotheriines did so through regular phalangeal fusion, whereas chalicotheriines achieved digit immobilisation through a different joint structure rather than formation of a true duplex bone. Hindlimbs and posture The hindlimbs and pelvis also differed between the two subfamilies. Schizotheriines had powerful hindlimbs and a body plan compatible with rearing while feeding, whereas chalicotheriines combined their elongated forelimbs with a postcranial skeleton that has often been interpreted as supporting upright and possibly seated feeding postures. These reconstructions are based on comparative functional morphology and are best treated as well-supported interpretations rather than direct observations of behaviour. Subfamily contrasts Taken together, the two chalicothere subfamilies represent different anatomical solutions to clawed browsing. Schizotheriines retained a more conventional quadrupedal stance and appear to have been functionally less specialised, while chalicotheriines evolved a more extreme forelimb-dominated body plan with greater emphasis on forelimb reach and branch manipulation. == Palaeobiology ==

Diet Dental microwear and mesowear studies indicate that chalicotheriids were browsers rather than grazers, and that grass did not form a significant part of their diet. The family as a whole appears to have fed mainly on leaves, but different genera also show evidence for tougher or more abrasive browse, including bark, twigs, and fruit with hard seeds or pits. Locomotion and feeding posture Functional interpretations of the postcranial skeleton indicate that chalicotheriids used their claws primarily in feeding rather than as digging tools. Coombs interpreted the family as a lineage of specialised browsing perissodactyls in which the forelimbs and hooked claws were used to pull branches within reach of the mouth. Their powerful hindlimbs and pelvic morphology suggest that at least some could rear up while feeding, using the claws of the forelimbs to draw down branches. Habitat Chalicotheriids are generally associated with wooded habitats, but the family did not occupy a single environment throughout its history. A chalicotheriine from the Miocene of Myanmar has been used to support the presence of an important closed-habitat component in the local palaeoenvironment, while the latest Central European Anisodon from Dorn-Dürkheim comes from a tropical savannah-to-woodland setting rather than a dense forest sensu stricto. Possible behaviour Direct evidence for chalicothere behaviour is limited, so most reconstructions are inferential. However, rarity in the fossil record does not by itself demonstrate solitary behaviour, and there is currently no secure basis for reconstructing detailed social systems across the family. == Systematics and taxonomy ==

Chalicotheres are part of the order Perissodactyla, which includes modern equines, rhinoceroses, and tapirs, as well as extinct relatives like brontotheres. 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 clade Ancylopoda alongside their close relatives Lophiodontidae. Many studies considered them as closer to Ceratomorpha (which includes tapirs and rhinoceroses) than Equoidea. A 2004 cladistic study alternatively recovered Ancylopoda as sister to all modern perissodactyls (which includes Equoidea and Ceratomorpha), with the brontotheres as the most distantly related within the order Perissodactyla. Chalicotheriidae is the family that includes the Oligocene and later chalicotheres, and it is generally divided into two subfamilies, Chalicotheriinae and Schizotheriinae. This division is based chiefly on cranial, dental and postcranial characters. Chalicotheriines typically have more robust jaws, a longer mandibular symphysis, low-crowned cheek teeth and the retention of lower canines, whereas schizotheriines generally have more slender mandibles, a shorter symphysis and more derived cheek teeth. Recent treatments place Winamia, Chalicotherium, Kalimantsia, Anisodon, Nestoritherium and Hesperotherium in the Chalicotheriinae. Later work revalidated Nestoritherium and suggested that Hesperotherium may be nested within it. Schizotheriinae includes Schizotherium, Borissiakia, Phyllotillon, Moropus, Tylocephalonyx, Metaschizotherium and Ancylotherium. Recent authors continue to follow the broad framework established by Margery Coombs for the diagnosis and internal relationships of the subfamily. Some names within the group remain problematic: for example, the taxonomy of Phyllotillon has been regarded as controversial because of the scarcity of material, and some authors have suggested restricting the genus to the Bugti collections of Pakistan until better fossils are available. The early African chalicotheriine formerly called Butleria rusingensis has been renamed Winamia rusingensis because Butleria was preoccupied. The generic placement of "Chalicotherium" pilgrimi remains unsettled in the literature, and some African late Neogene material has been referred to "Chemositia" tugenensis with caution rather than full confidence in the generic assignment. Genera == Evolution, biogeography and fossil record ==

The superfamily Chalicotherioidea first appeared in the Eocene in Asia, with the earliest chalicotheriids proper appearing during the following Oligocene. By the late Oligocene, they had divided into schizotheriines and chalicotheriines. The family reached its greatest diversity in the Miocene. The early Miocene Lanzhou Basin fauna, for example, preserves a schizotheriine close to Borissiakia, while later Asian assemblages include advanced chalicotheriines such as Nestoritherium and Hesperotherium. Schizotheriines were widespread in Europe during the middle Miocene, especially in the genus Metaschizotherium, whereas chalicotheriines such as Anisodon and later Balkan forms such as Kalimantsia are characteristic elements of later Miocene faunas. Late Miocene localities in Romania and the Eastern Mediterranean are especially important because they document coexistence of the two subfamilies in the same broad region. The palaeobiogeographic history of the family also shows that the two subfamilies did not always share the same distribution or ecological settings. The youngest chalicotheres are the chalicotheriines Hesperotherium from the Early Pleistocene of China, Nestoritherium from the Early Pleistocene of Myanmar, as well as the schizotheriine Ancylotherium from the Early Pleistocene of Eastern and Southern Africa, also possibly known from the Early Pleistocene of China. In China, Hesperotherium is suggested to have survived until the near the end of the Early Pleistocene, around 1 million years ago. ==References==