Elasmotherium is a big rhinoceros genus that was unique to Eurasia from the Late Pliocene to the Pleistocene, surviving from 2.6 Ma to at least 39,000 years ago in the Late Pleistocene. It was the last surviving member of the Elasmotheriinae family of rhinoceroses, which split from living rhinoceroses at least 35 million years ago, according to fossils, and around 47.4 million years ago, according to a molecular clock.
Rhinoceroses are separated into two subfamilies, Rhinocerotinae and Elasmotheriinae, which split about 47.3 million years ago, or 35 million years ago at the most. Others became extinct with the spread of savannas, and Elasmotherium is the only known member of the latter from after the Miocene. Elasmotherium first arose in the Late Pliocene, and it is thought to be a descendant of Miocene—Pliocene Sinotherium. Elasmotherium, on the other hand, was shown to be most closely linked to the woolly rhinocerotine in a 1995 cladistic analysis.
Elasmotheriinae are thought to have hypsodonty, a dentition pattern in which the molars have high crowns, and the enamel extends below the gum line, possibly as an adaptation to the heavier grains found in riparian zones on riverbanks.
Elasmotherium, like other rhinos, lacks incisors and canines, depending instead on a prehensile lip to remove food. Elasmotherium were euhypsodonts, meaning they had huge tooth crowns, enamel that extended below the gum line, and teeth that were constantly growing. The presence of tooth roots in Elasmotherium fossils is unusual.
Elasmotherium is considered to have had a keratinous horn with a 5-inch (13 cm) deep wrinkled surface and a circumference of 3 feet, as suggested by a circular dome on the forehead (0.91 m). The furrows are thought to be the locations of horn-generating tissue’s blood vessels.
The horn of a rhinoceros does not develop from bone, but rather from the surface of dense skin tissue, anchoring itself by producing bone abnormalities and rugosities. Cornification occurs in the outermost layer. The horn loses diameter as the layers age owing to keratin degradation caused by ultraviolet exposure, drying, and constant use. Melanin and calcium deposits in the center, on the other hand, harden the keratin, giving the horn its unique shape. There was most likely a massive muscle hump on the back, which would have supported a heavy horn.
Modern hypsodont hoofed mammals are mostly open-air grazers, with hypsodonty likely being an adaptation for chewing tough, fibrous grass. Elasmotherium dental wear is similar to that of grazing white rhinos, and both have a downward orientation on their heads, indicating a similar lifestyle and capacity to only reach low-lying plants. Elasmotherium’s head had the most obtuse angle of any rhinoceros, and it could only reach the lowest elevations, implying that it grazed frequently. Elasmotherium also has euhypsodonty, which is more common in rodents, and its dental physiology may have been impacted by scavenging food from moist, gritty dirt. As a result, they may have lived in both mammoth steppe and riparian riverbanks, comparable to modern mammoths.
Elasmotherium was traditionally assumed to have died out approximately 200 Kya due to natural extinction, but E. sibiricum skull remains from Kazakhstan’s Pavlodar Region reveal that it survived in the Western Siberian Plain circa 36–35 Kya. The Siberian Smelovskaya and Batpak Caves have isolated bones going back to 50 Kya, which were most likely brought there by a predator. This coincides roughly with the Pleistocene extinction, when anything weighing more than 45 kilograms perished, as well as a transition to a cooler climate–resulting in the replacement of grasses and herbs by lichens and mosses–and the arrival of modern people in the area.