''Trigonias'' (Greek: "triangular" (trigonos), "ias" enotes possession is an extinct genus of

rhinocerotid A rhinoceros ( ; ; ; : rhinoceros or rhinoceroses), commonly abbreviated to rhino, is a member of any of the five extant taxon, extant species (or numerous extinct species) of odd-toed ungulates (perissodactyls) in the family (biology), famil ...

from the late

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

(

Chadronian The Chadronian is a North American Land Mammal Age typically set from around 37,000,000 to 33,700,000 years BP, a period of . The Chadronian is preceded by the Duchesnean and followed by the Orellan NALMA stages. Relative to global geological c ...

) some 35 million years ago of

North America North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...

. ''Trigonias'' was about long and, despite lacking

horn Horn may refer to: Common uses * Horn (acoustic), a tapered sound guide ** Horn antenna ** Horn loudspeaker ** Vehicle horn ** Train horn *Horn (anatomy), a pointed, bony projection on the head of various animals * Horn (instrument), a family ...

s, looked a lot like modern rhinos. Its front legs had five toes (as contrasted with three in modern rhinos), the fifth of which was

vestigial Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...

. A specimen of ''T. osborni'' was estimated to have a weight of about .Paleobiology Database
Cladogram after Lu, Deng and Pandolfi, 2023:

Notes

References

*Prothero, Donald R. 2005. ''The Evolution of North American Rhinoceroses.'' Cambridge University Press, Cambridge, 218 pp. Eocene rhinoceroses Eocene Perissodactyla Eocene mammals of North America White River Fauna Fossil taxa described in 1900 {{paleo-oddtoedungulate-stub