Elasmotherium is an extinct genus of large rhinoceros endemic to Eurasia during the Late Pliocene through the Pleistocene, existing from 2.6 Ma to at least as late as 39,000 years ago in the Late Pleistocene. A more recent date of 26,000 BP is considered less reliable.
Three species are recognized. The best known, E. sibiricum, was the size of a mammoth and is thought to have borne a large, thick horn on its forehead. Theories about the function of this horn include defense against predators, attracting mates, driving away competitors, sweeping snow from the grass in winter, and digging for water and plant roots. Like all rhinoceroses, elasmotheres were herbivorous. Unlike any other rhinos, its high-crowned molars were ever-growing. Its legs were longer than those of other rhinos and were adapted for galloping, giving it a horse-like gait.
Elasmotherium was first described in 1809 by German/Russian palaeontologist Gotthelf Fischer von Waldheim based on a left lower jaw, four molars, and the tooth root of the third premolar, which was gifted to Moscow University by princess Ekaterina Dashkova in 1807. He first announced it at an 1808 presentation before the Moscow Society of Naturalists. The genus name derives from Ancient Greek elasmos “laminated” and therion “mammal” in reference to the laminated folding of the tooth enamel; and the species name sibericus is probably a reference to the predominantly Siberian origin of princess Dashkova’s collection. However, the specimen’s exact origins are unknown. In 1877, German naturalist Johann Friedrich von Brandt placed it into the newly erected subfamily Elasmotheriinae, separate from modern rhinos.
In 1997, the McKenna/Bell classification considered Elasmotherium to be closely related to the wooly and modern rhinos, and placed it into the subfamily Rhinocerotinae.
The genus is known from hundreds of find sites, mainly of cranial fragments and teeth, but in some cases nearly complete skeletons of post-cranial bones, scattered over Eurasia from Eastern Europe to China. Dozens of crania have been reconstructed and given archaeological identifiers. The division into species is based mainly on the fine distinctions of the teeth and jaws and the shape of the skull.
An elasmotherian species turned up in the preceding Khaprovian or Khaprov Faunal Complex, which was at first taken to be E. caucasicum, and then on the basis of the dentition was redefined as a new species, E. chaprovicum (Shvyreva, 2004), named after the Khaprov Faunal Complex. The Khaprov is in the Middle Villafranchian, MN17, which spans the Piacenzian of the Late Pliocene and the Gelasian of the Early Pleistocene of Northern Caucasus, Moldova and Asia and has been dated to 2.6–2.2 Ma.
E. caucasicum was first described by Russian palaeontologist Aleksei Borissiak in 1914, who said it apparently flourished in the Black Sea region as a member of the Early Pleistocene Tamanian Faunal Unit (1.1–0.8 Ma, Taman Peninsula). It is the most commonly found mammal of the assemblage. E. caucasicum is thought to be more primitive than E. sibiricum and perhaps represents an ancestral stock. It is also known in northern China from the Early Pleistocene Nihewan Faunal assemblage and were extinct at approximately 1.6 Ma. This suggests Elasmotherium developed separately in Russia and China.
Rhinoceroses are divided into two subfamilies, Rhinocerotinae and Elasmotheriinae, which diverged perhaps 47.3 mya, 35 mya at the latest. Elasmotherium is the only known member of the latter from after the Miocene, others becoming extinct with the expansion of savannas. Elasmotherium appeared in the Late Pliocene, apparently deriving from the Miocene—Pliocene Sinotherium. However, a 1995 cladistic analysis asserted that Elasmotherium was most closely related to the wooly rhino, a rhinocerotine.
Elasmotherium is typically reconstructed as a woolly animal, generally based on the woolliness exemplified in contemporary megafauna such as mammoths and the woolly rhino. However, it is sometimes depicted as bare-skinned like modern rhinos. In 1948, Russian palaeontologist Valentin Teryaev suggested it was semi-aquatic with a dome-like horn, and resembled a hippo because the animal had 4 toes like a wetland tapir rather than the 3 toes in other rhinos, but Elasmotherium has since been shown to have had only 3 functional toes, and Teryaev’s reconstruction has not garnered much scientific attention.
The known specimens of E. sibiricum reach up to 4.5 m (15 ft) in length, with shoulder heights of over 2 m (6 ft 7 in), while E. caucasicum reaches at least 5 m (16 ft) in body length with an estimated mass of 3.6–4.5 tonnes (4–5 short tons), making Elasmotherium the largest rhinos of the Quaternary. Both species were among the largest rhinos, comparable in size to the woolly mammoth and larger than the contemporary woolly rhinoceros. The feet were unguligrade, the front larger than the rear, with 3 digits at the front and rear, with a vestigial fifth metacarpal.