''Chilotherium'' is an

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

rhinocerotid A rhinoceros ( ; ; ; : rhinoceros or rhinoceroses), commonly abbreviated to rhino, is a member of any of the five extant taxon, extant species (or numerous extinct species) of odd-toed ungulates (perissodactyls) in the family (biology), famil ...

s lived in

Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...

and

Eurasia Eurasia ( , ) is a continental area on Earth, comprising all of Europe and Asia. According to some geographers, Physical geography, physiographically, Eurasia is a single supercontinent. The concept of Europe and Asia as distinct continents d ...

during the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

through

Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58mya, existing for approximately .. Retrieved 19 May 2013.

Description

It was a large, robust animal reaching 1.5-1.8 m in height and a weight between 1 and 2.5

ton Ton is any of several units of measure of mass, volume or force. It has a long history and has acquired several meanings and uses. As a unit of mass, ''ton'' can mean: * the '' long ton'', which is * the ''tonne'', also called the ''metric ...

s, depending on the species. Both sexes are hornless. The lower jaw has a widened symphysial part and large tusk-like second incisors separated by a broad

diastema A diastema (: diastemata, from Greek , 'space') is a space or gap between two teeth. Many species of mammals have diastemata as a normal feature, most commonly between the incisors and molars. More colloquially, the condition may be referred to ...

. The dental formula is . The limbs are very short and the body stout; the feet are tridactyl with diverging metapodials. At least in ''C. wimani'', there is a significant

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

in the tusks and mandible, most notably the length of the tusks in males. Some features in ''Chilotherium'', such as second incisors, mandible, cheek-teeth and other cranial features, may be

plesiomorphic In phylogenetics, a plesiomorphy ("near form") and symplesiomorphy are synonyms for an ancestral character shared by all members of a clade, which does not distinguish the clade from other clades. Plesiomorphy, symplesiomorphy, apomorphy, an ...

, while some features in the tusks are apomorphic: the dorsal surface of the tusks in primitive species is turned latero-dorsally in more derived species while the medial edge has become very sharp and sickle-like and rotated dorsally, and thus a more effective cutting tool. ''Chilotherium'' were a group of

grazing In agriculture, grazing is a method of animal husbandry whereby domestic livestock are allowed outdoors to free range (roam around) and consume wild vegetations in order to feed conversion ratio, convert the otherwise indigestible (by human diges ...

animals that radiated into several subgenera and species. Their feet were tridactyl and their legs shorter than in related groups. A few of them remained

browsers Browse, browser, or browsing may refer to: Computing *Browser service, a feature of Microsoft Windows to browse shared network resources *Code browser, a program for navigating source code *File browser or file manager, a program used to manage f ...

, but most of them were adapted to a grass-based diet, hence the short legs. Their heads were horn-less but equipped with tusk-like lower incisors and were held in a horizontal position, in contrast to modern rhinos. They inhabited the so-called sub- Paratethyan or Greek-Iranian province during the late Miocene when this region was invaded by advanced rhinos from Africa, such as ''

Ceratotherium ''Ceratotherium'' (from Greek: ''keras'' κέρας "horn" and ''thērion'' θηρίον "beast") is a genus within the family Rhinocerotidae. It comprises one living species, the white rhinoceros (''Ceratotherium simum''), and several extinct fo ...

'' (modern white rhinos). Like them, ''Chilotherium'' gradually evolved into specialised grazers, including

hypsodont Hypsodont is a pattern of dentition characterized by with high crowns, providing extra material for wear and tear. Some examples of animals with hypsodont dentition are cows and horses; all animals that feed on gritty, fibrous material. The oppos ...

teeth and shortened metapodials. Recent studies have confirmed the grazing nature of ''C. schlosseri''.

Taxonomy

''Chilotherium'' was named by Ringström in 1924. It was assigned to ''Rhinocerotidae'' by Carroll (1988); to '' Aceratheriini'' by Antoine and Saraç (2005); and to '' Chilotheriini'' by Deng (2005).

Species

Twelve species of ''Chilotherium'' have been described and 19 other species have been assigned the genus. Nine are considered valid: four from Europe, one from Iran, and four from China. '' Aprotodon'' differs from ''Chilotherium'' in its proportionally larger and wider symphysis; the horizontal mandibular ramus is curved both in side view and in dorsal view, unlike most rhinocerotids; and the premolars are semi-molariform, unlike the fully molariform premolars in ''Chilotherium''. In '' Subchilotherium'' the mandibular symphysis is much more narrow than in ''Chilotherium''. '' Acerorhinus'' has a strongly constricted nasal base and a mandibular symphysis that is narrow compared to that in ''Chilotherium''.

Pathology

A female ''Chilotherium'' skull bears the distinctive bite marks of '' Dinocrocuta gigantea'' on the forehead. Based on the regrowth of bone around the injury, the rhinoceros escaped the predator's attack and later recovered.

Notes

References

* * * * * * * {{Taxonbar, from=Q19389 Miocene rhinoceroses Pliocene extinctions Prehistoric mammals of Asia Prehistoric mammals of Europe Pliocene rhinoceroses Fossil taxa described in 1924