The woolly rhinoceros (Coelodonta antiquitatis) is an extinct species of rhinoceros that inhabited northern Eurasia during the Pleistocene epoch. The woolly rhinoceros was large, comparable in size to the largest living rhinoceros species, the white rhinoceros (Ceratotherium simum), and covered with long, thick hair that allowed it to survive in the extremely cold, harsh mammoth steppe. It had a massive hump reaching from its shoulder and fed mainly by grazing on herbaceous plants that grew in the steppe. Mummified carcasses preserved in permafrost and many bone remains of woolly rhinoceroses have been found. Images of woolly rhinoceroses are found among cave paintings in Europe and Asia, and evidence has been found suggesting that the species was hunted by humans. Like other Pleistocene megafauna, the species became extinct as part of the end-Pleistocene extinction event. The range of the woolly rhinoceros contracted towards Siberia beginning around 17,000 years ago, with the youngest reliable records being around 14,000 years old in northeast Siberia, coinciding with the Bølling–Allerød warming, which likely disrupted its habitat, with environmental DNA records possibly extending the range of the species around 9,800 years ago. Its closest living relative is the Sumatran rhinoceros (Dicerorhinus sumatrensis).
Taxonomy
Woolly rhinoceros remains have been known long before the species was described and were the basis for some mythical creatures. Native peoples of Siberia believed their horns were the claws of giant birds. A rhinoceros skull was found in Klagenfurt, Austria, in 1335, and was believed to be that of a dragon. In 1590, it was used as the basis for the head on a statue of a lindworm. Gotthilf Heinrich von Schubert maintained the belief that the horns were the claws of giant birds, and classified the animal under the name Gryphus antiquitatis, meaning "griffin of antiquity".Schubert, von, G. H., 1823. Die Urwelt und die Fixsterne: eine Zugabe zu den Ansichten von der Nachtseite der Naturwissenschaft [The Primeval World and the Fixed Stars]. Arnoldischen Buchhandlung, Dresden.
One of the earliest scientific descriptions of an ancient rhinoceros species was made in 1769, when the naturalist Peter Simon Pallas wrote a report on his expeditions to Siberia where he found a skull and two horns in the permafrost. In 1772, Pallas acquired a head and two legs of a rhinoceros from the locals in Irkutsk, and named the species Rhinoceros lenenesis (after the Lena River). In 1799, Johann Friedrich Blumenbach studied rhinoceros bones from the collection of the University of Göttingen, and proposed the scientific name Rhinoceros antiquitatis.Gehler, Alexander & Reich, Mike & Mol, Dick & Plicht, Hans. (2007). The type material of Coelodonta antiquitatis (Blumenbach) (Mammalia: Perissodactyla: Rhinocerotidae) / Типовой материал Coelodonta antiquitatis (Blumenbach) (Mammalia: Perissodactyla: Rhinocerotidae) / Tipovoj material Coelodonta antiquitatis (Blumenbach) (Mammalia: Perissodactyla: Rhinocerotidae). The geologist Heinrich Georg Bronn moved the species to Coelodonta in 1831 because of its differences in dental formation with members of the Rhinoceros genus. This name comes from the Greek words κοιλος (koilos, "hollow") and ὀδούς (odoús "tooth"), from the depression in the rhino's molar structure, giving the scientific name Coelodonta antiquitatis, "hollow-tooth of antiquity".
Evolution The woolly rhinoceros was the most recent species of the genus Coelodonta. The closest living relative of Coelodonta is the Sumatran rhinoceros, and the genus is also closely related to the extinct genus Stephanorhinus. A cladogram showing the relationships of C. antiquitatis to other Late Pleistocene-recent rhinoceros species based on genomic data is given below.
Relationships of the woolly rhinoceros based on morphology, excluding African rhinoceros species:The ancestors of Coelodonta are suggested to have diverged from those of the Sumatran rhinoceros around 9.4 million years ago, with Coelodonta diverging from Stephanorhinus around 5.5 million years ago. The oldest known species of Coelodonta, Coelodonta thibetana is known from the Pliocene of Tibet dating to approximately 3.7 million years ago, with the genus being present in Siberia, Mongolia, and China during the Early Pleistocene. The woolly rhinoceros first appeared during the early Middle Pleistocene in China, and the oldest remains of the species in Europe, which represents the only species of Coelodonta to have been present in the region, date to approximately 450,000 years ago. The woolly rhinoceros is divided into two chrono-subspecies, with C. a. praecursor from the middle Pleistocene and C. a. antiquitatis from the late Pleistocene. Mitochondrial genomes suggest that the last mitochondrial ancestor of Late Pleistocene woolly rhinoceroses lived around 570,000 years ago. There appears to have been some interbreeding between Merck's rhinoceros (Stephanorhinus kirchbergensis) and the woolly rhinoceros in Eastern Eurasia during the Late Pleistocene.
Description Size and general morphology An adult woolly rhinoceros typically measured from head to tail, stood tall at the shoulder, and weighed up to (with some sources estimate the species' maximum shoulder height at and its weight at ) making it comparable in size to the largest living rhinoceros species, the white rhinoceros (Ceratotherium simum). Compared to other rhinoceroses, the woolly rhinoceros had a longer head and body, and shorter legs.
Like the living white rhinoceros, the shoulder was at least sometimes raised with a substantial hump, which may have developed to support the weight of the animal’s large head and horns. Unlike the hump of the white rhinoceros, the hump of the woolly rhinoceros contained substantial fat reserves (probably predominantly white fat), the most substantial on the entire body. The hump likely served for thermoregulation (reducing the surface-area-to-volume ratio to make keeping the body warm more efficient) and/or as a storage for energy gained during warmer months to use during cold months. Aside from depictions in cave paintings, a hump is only definitively known from a single mummified subadult specimen (around 4–4.5 years old), and it is possible that the hump was a juvenile only feature or that the size/presence of the hump varied seasonally.
Skull and dentition
The skull had a length between . It was longer than those of other rhinoceros, giving the head a deep, downward-facing slanting position, similar to its fossil relative Stephanorhinus hemitoechus and Elasmotherium as well as the white rhinoceros. Strong muscles on its long occipital bone formed its neck hock and held the massive skull. Its massive lower jaw measured up to long and high. The teeth of the woolly rhinoceros had thickened enamel and an open internal cavity. Like other rhinos, adults did not have incisors. It had 3 premolars and 3 molars in both jaws. The molars were high-crowned and had a thick coat of cementum.
Both males and females had two horns which were made of keratin, with one long nasal horn at the front of the skull reaching forward and a smaller posterior frontal horn between the eyes. The nasal horn would have typically measured long for individuals at 25 to 35 years of age, while the frontal horn would have measured up to long, with the mass of measured woolly rhinoceros nasal horns varing from , with an average mass of . The longest nasal horn ever recorded is long measured along the curvature. Unlike in modern rhinos, the large nasal horn was often flattened in cross-section, and abrasion patterns on the horn indicate its possible use in brushing away snow when grazing.
The nasal septum of the woolly rhinoceros was ossified, unlike modern rhinos. This was most common in adult males. This adaptation probably evolved as a result of the heavy pressure on the horn and face when the rhinoceros grazed underneath the thick snow. Unique to this rhino, the nasal bones were fused to the premaxillae, which is not the case in older Coelodonta types or today's rhinoceroses. This ossification inspired the junior synonym specific name tichorhinus, from Greek τειχος (teikhos) "wall", ῥις (ῥιν-) (rhis (rhin-)) "nose".
External appearance Frozen specimens indicate that the woolly rhino's long fur coat was brown in adults and light brown in juveniles, with a thick undercoat that lay under a layer of long, coarse guard hair thickest on the withers and neck. Shorter hair covered the limbs, keeping snow from attaching. The body's length ended with a tail with a brush of coarse hair at the end.Kalandadze N. N., Shapovalov A. V. & Tesakova E. M. — On nomenclatural problems concerning woolly rhinoceros Coelodonta antiquitatis (Blumenbach, 1799) // Researches on paleontology and biostratigraphy of ancient continental deposits (Memories of Professor Vitalii G. Ochev). Eds. M. A. Shishkin & V. P. Tverdokhlebov. — Saratov: «Nauchnaya Kniga» Publishers, 2009. P. 98–111. Females had two nipples on the udders.
The woolly rhinoceros had several features which reduced the body's surface area and minimized heat loss. Its ears were no longer than , while those of rhinos in hot climates are about . Their tails were also relatively shorter. It also had thick skin, ranging from , heaviest on the chest and shoulders. Beneath the skin, the body was covered in a layer of subcutaneous fat, ranging from thick on the chest, to on the lower jaw and the posterior part of the back.
Paleobiology and palaeoecology
The woolly rhinoceros had a similar life history to modern rhinos. Studies on milk teeth show that individuals developed similarly to both the white and black rhinoceros. The two teats in the female suggest that she raised one calf, or more rarely two, every two to three years.
With their massive horns and size, adults had few predators, but young individuals could have been killed and consumed by predators such as cave hyenas and cave lions. A skull from the Volga region of Russia was found with trauma suggested to have been inflicted by a cave lion when it was a juvenile, but the animal survived to adulthood. Remains of woolly rhinoceros are frequently found in cave hyena dens with gnaw marks indicating that their remains were consumed by them,Diedrich, C. G. & ŽÁK, K. 2006. Prey deposits and den sites of the Upper Pleistocene hyena Crocuta crocuta spelaea (Goldfuss, 1823) in horizontal and vertical caves of the Bohemian Karst (Czech Republic). Bulletin of Geosciences 81(4), 237–276 (25 figures). Czech Geological Survey, Prague. ISSN 1214-1119. which to a large degree likely reflects scavenging of the carcasses of already dead rhinoceroses. A piece of juvenile woolly rhinoceros skin with blond fur (possibly representing that of a calf) was recovered from the stomach content of two frozen juvenile female Pleistocene wolves, which was inferred to be part of the wolves' last meal.
Woolly rhinos may have used their horns for combat, probably including intraspecific combat as recorded in cave paintings, as well as for moving snow to uncover vegetation during winter. They may have also been used to attract mates. Bull woolly rhinos were probably territorial like their modern counterparts, defending themselves from competitors, particularly during the rutting season. Fossil skulls indicate damage from the front horns of other rhinos, and lower jaws and back ribs show signs of being broken and re-formed, which may have also come from fighting. The apparent frequency of intraspecific combat, compared to recent rhinos, was likely a result of rapid climatic change during the last glacial period, when the animal faced increased stress from competition with other large herbivores.
Diet