Chilotherium
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Chilotherium Temporal range: Late Miocene–Pliocene |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Perissodactyla |
| Family: | Rhinocerotidae |
| Subfamily: | Aceratheriinae |
| Genus: |
Chilotherium Ringström 1924 |
| Species | |
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See text |
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See text
Chilotherium is an extinct genus of rhinoceros endemic to Eurasia during the Miocene through Pliocene living for 13.7—3.4 mya, existing for approximately 10.3 million years.
It was a large, robust animal reaching 1.5-1.8 m in height and a weight between 1 and 2.5 tons, depending on the species.
Both sexes are horn-less. The lower jaw has a widened symphysial part and large tusk-like second incisors separated by a broad diastema. The dental formula is 0.0.3.31(2).0.3.3. The limbs are very short and the body stout; the feet are tridactyl with diverging metapodials. Studying C. wimani, Chen et al. 2010 found a significant sexual dimorphism in the tusks and mandible, most notably the length of the tusks in males.
Geraads & Spassov 2009 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 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, 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 teeth and shortened metapodials.
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