''Trigonias'' (Greek: "triangular" (trigonos), "ias"

enotes possession eNotes was a free student and teacher educational website founded in 1998 by Brad Satoris and Alexander Bloomingdale, that provides material to help students complete homework assignments and study for exams. Based in Seattle, Washington, eNote ...

is an extinct genus of

rhinoceros A rhinoceros (; ; ), commonly abbreviated to rhino, is a member of any of the five extant taxon, extant species (or numerous extinct species) of odd-toed ungulates in the family (biology), family Rhinocerotidae. (It can also refer to a member ...

from the late

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

(

Chadronian The Chadronian age within the North American Land Mammal Ages chronology is the North American faunal stage typically set from 38,000,000 to 33,900,000 years BP, a period of . It is usually considered to fall within the Eocene epoch. The Chadroni ...

) some 35 million years ago of North America. ''Trigonias'' was about long and, despite lacking

horn Horn most often refers to: * Horn (acoustic), a conical or bell shaped aperture used to guide sound ** Horn (instrument), collective name for tube-shaped wind musical instruments * Horn (anatomy), a pointed, bony projection on the head of various ...

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 .http://paleodb.org/cgi-bin/bridge.pl?a=basicTaxonInfo&taxon_no=52444

Notes

References

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