genus
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...
of
rhinoceros
A rhinoceros (; ; ), commonly abbreviated to rhino, is a member of any of the five extant species (or numerous extinct species) of odd-toed ungulates in the family Rhinocerotidae. (It can also refer to a member of any of the extinct species ...
endemic to
Eurasia
Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago ...
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 in the geologic time scale that extends from 5.333 million 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 the name of any one of several units of measure. It has a long history and has acquired several meanings and uses.
Mainly it describes units of weight. Confusion can arise because ''ton'' can mean
* the long ton, which is 2,240 pounds
...
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 (plural diastemata, from Greek διάστημα, 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 ...
. The dental formula is . The limbs are very short and the body stout; the feet are tridactyl with diverging metapodials.
Studying ''C. wimani'', found a significant
sexual dimorphism
Sexual dimorphism is the condition where the sexes of the same animal and/or plant species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction. The condition occurs in most an ...
in the tusks and mandible, most notably the length of the tusks in males.
argued that some features in ''Chilotherium'', such as second incisors, mandible, cheek-teeth and other cranial features, are plesiomorphic, 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 roam around and consume wild vegetations in order to convert the otherwise indigestible (by human gut) cellulose within grass and other ...
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:
Programs
* Web browser, a program used to access the World Wide Web
*Code browser, a program for navigating source code
* File browser or file manager, a program used to manage files and related objects
* ...
, 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'' (modern white rhinos). Like them, ''Chilotherium'' gradually evolved into specialised grazers, including
hypsodont
Hypsodont is a pattern of dentition with high-crowned teeth and enamel extending past the gum line, providing extra material for wear and tear. Some examples of animals with hypsodont dentition are cows and horses; all animals that feed on gritt ...
teeth and shortened
metapodial Metapodials are long bones of the hand (metacarpals) and feet (metatarsal
The metatarsal bones, or metatarsus, are a group of five long bones in the foot, located between the tarsal bones of the hind- and mid-foot and the phalanges of the toes ...
s.
Taxonomy
''Chilotherium'' was named by . 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
''Dinocrocuta'' is an extinct genus of hyena-like feliform carnivores. It lived in Asia, and Africa, during the Miocene
The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Mi ...
'' on the forehead. Based on the regrowth of bone around the injury, the rhinoceros escaped the predator's attack and later recovered.