The Six-Horned Beast — Uintatherium

Do you enjoy reading Journey to the West? Besides paleontology, Rodrigo has always loved mythological stories, especially legends about the fantastic beasts described in different cultures. The prehistoric animal introduced today resembles one such creature: Diting, the mythical mount of the bodhisattva Kṣitigarbha in Journey to the West. According to the novel, Diting possesses the head of a tiger, the horn of a rhinoceros, the ears of a dog, the body of a dragon, the tail of a lion, and the hooves of a qilin.

The animal in today's story carries an equally bizarre mixture of features: tiger-like tusks, rhinoceros-like horns, deer-like antlers, and the body of an elephant. This remarkable creature is Uintatherium.

Portrait of Diting, painted in the 10th century, Dunhuang; currently housed at the Musée Guimet, Paris.（圖片來源：Musee Guimet，CC0 1.0 公共領域）

Uintatherium—whose name means “the beast of the Uinta Mountains”—was a large mammal that lived during the Eocene, from the Lutetian to the Priabonian stages. Adults reached about 1.7 meters in shoulder height and roughly 4 meters in body length, with an estimated body mass of around two tonnes. In the ecosystems of its time, it was unquestionably a giant.

Localities where Uintatherium fossils have been discovered.

Geological time range of Uintatherium.（白稜製作）

The appearance of Uintatherium was extraordinarily unusual. Males bore three pairs of bony horn-like protuberances on the skull, for a total of six. These structures were covered by skin and hair and were structurally similar to the ossicones of modern giraffes. In addition to these peculiar horns, the animal possessed a pair of enlarged canine teeth that formed long saber-like tusks reminiscent of those of saber-toothed cats. Despite these intimidating weapons, Uintatherium was an herbivore.

Paleontologists suggest that the horns and tusks were likely the result of sexual selection. Evidence for this interpretation comes from the strong sexual dimorphism observed in the species: males possessed larger horns and tusks than females. Male individuals may have used these structures to compete with rivals for territory or access to mates.

Reconstruction of Uintatherium.（圖片來源：Dmitry Bogdanov，採用 CC BY-SA 3.0 授權）

To support such contests, the skull of Uintatherium evolved to become extremely robust. The top of the skull was somewhat concave, a feature also seen in the brontotheres. Yet such an enormous head inevitably placed strain on the neck. To reduce the weight of the skull, the bones developed numerous internal air-filled cavities, while the cranial cavity that housed the brain became relatively small.

Cast of a Uintatherium skull, photographed at the National Museum of Natural History, France.（圖片來源：Jebulon，CC0 1.0 公共領域）

As a herbivore, Uintatherium favored forested and swampy habitats. Analyses of fossil teeth suggest that it mainly consumed low-growing shrubs and marsh plants, occasionally feeding on the young leaves of broadleaf trees and other dicotyledonous plants. Its feeding behavior may have resembled that of modern hippopotamuses: the large tusks could be used to cut aquatic vegetation, while the molars crushed and ground plant material. However, the dentition of Uintatherium remained relatively primitive, which likely limited its ability to process tougher plant tissues such as roots or bark.

19th-century reconstruction of Uintatherium.（圖片來源：Charles Robert Knight，CC0 1.0 公共領域）

The limbs of Uintatherium were also unusual. Its skeleton resembled that of a rhinoceros in overall robustness, yet the arrangement of the toes was more reminiscent of elephants, forming a semi-digitigrade structure. Despite these similarities, Uintatherium belonged neither to the order Perissodactyla (which includes rhinoceroses) nor to the Afrotheria, the group that contains elephants. Instead, it belonged to a distinct and enigmatic order known as Dinocerata.

Dinocerates remain one of the more mysterious mammalian lineages. Paleontologists still debate their precise evolutionary origins and closest relatives. Fossil evidence suggests that the group first appeared in Mongolia and, during the Paleocene-Eocene Thermal Maximum, spread rapidly across Asia and North America as forests expanded across the continents.

Reconstruction of an early dinocerate, Prodinoceras.（圖片來源：Apokryltaros，採用 CC BY-SA 3.0 授權）

This prosperity did not last indefinitely. After the Paleocene-Eocene Thermal Maximum ended, Earth's climate gradually became cooler and drier. Wetland environments—essential for animals such as Uintatherium—began to shrink. At the same time, the rise of large herbivores such as the brontotheres further compressed the ecological space available to these giants. Eventually, by the Priabonian stage of the Eocene, the uintatheres disappeared entirely from the fossil record.

Although Uintatherium is relatively obscure in modern biology, it occupies a surprisingly prominent place in the history of paleontology. The reason lies in one of the most famous rivalries in scientific history: the Bone Wars.

During this intense fossil-hunting competition between Othniel Charles Marsh (1831–1899) and Edward Drinker Cope (1840–1897), Uintatherium became entangled in a chaotic series of competing names. In total, the animal accumulated as many as twenty-five synonymous or questionable names.

Detailed fossil localities of Uintatherium in the United States.（圖片來源：Leptictidium，採用 CC BY-SA 3.0 授權）

The story began in 1872, when Joseph Leidy (1823–1891), Cope's mentor, named a fossil from the Bridger Basin as belonging to the genus Uintatherium. Only eighteen days later, Marsh reexamined fossils that had been discovered together with Leidy and proposed a different genus, Tinoceras, emphasizing the large horns of the skull.

Coincidentally, that same year Cope discovered similar fossils in the nearby Washakie Basin. Noting their resemblance to the teeth of elephants, he named them Loxolophodon. Because these names were published within the same year, both scientists quickly learned of each other's claims and began a heated dispute.

Marsh fired the first shot by criticizing Cope's naming as invalid and introducing a new name, Tinoceras grande. Cope retaliated the following year, dismissing Marsh's proposal and naming another set of fossils Eobasileus galeatus. The two rivals continued attacking each other—arguing over anatomical details as well as naming conventions—until about 1885.

Reconstruction of Uintatherium imagined by Edward Drinker Cope, illustrated in 1873.（圖片來源：Edwin Sheppard，CC0 1.0 公共領域）

Skeleton of Uintatherium, exhibited at the National Museum of Natural History in Paris.（圖片來源：Shadowgate，採用 CC BY 2.0 授權）

As a result of this prolonged dispute, the animal's taxonomy remained confused for decades. Only in the modern era did paleontologists, particularly those at Princeton University, finally stabilize the nomenclature and consolidate these various names under Uintatherium.

The story of Uintatherium serves as a reminder of how destructive human rivalries can be. Scientific progress stalled for years—and even decades—because of personal conflicts. If these ancient beasts had truly possessed the wisdom attributed to mythical creatures such as Diting—capable of discerning truth and reconciling opposing views—perhaps the fate of their scientific history might have unfolded very differently.

Author: Rodrigo

Reference:

1. B. J., Journalism. "Ksitigarbha: Bodhisattva of the Buddhist Hell Realm"

2. Donald r. prothero. (2016). The Princeton Field Guide to Prehistoric Mammals. Princeton University Press.

3. Burger, Benjamin J. (2015). "The systematic position of the saber-toothed and horned giants of the Eocene: the Uintatheres (Order Dinocerata)" (PDF). Utah State University Uintah Basin Campus, Vernal, UT, 84078, United States Of America.

4. Leidy, Joseph (1873). "Contribution to the extinct vertebrate fauna of the Western Territories". Geological Survey of the Territories.

5. Wheeler, W. H. (1961). "Revision of the Uintatheres" (PDF). Peabody Museum of Natural History Bulletin. 14. Yale University.

6. Cope, Edward (1872). "Telegram describing extinct Proboscidians from Wyoming". Paleontological Bulletin.

7. Wheeler, W. H. (1960). "The uintatheres and the Cope–Marsh war". Science

8. Scott, W. B. (1886). "On some new forms of the Dinocerata". Am. Jour. Sci. 31 (3): 303–307.