Trigonias is an extinct genus of rhinoceros

Rhinoceros

Rhinoceros , also known as rhino, is a group of five extant species of odd-toed ungulates in the family Rhinocerotidae. Two of these species are native to Africa and three to southern Asia....

 from the late Eocene

Eocene

The Eocene Epoch, lasting from about 56 to 34 million years ago , is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Palaeocene Epoch to the beginning of the Oligocene Epoch. The start of the...

 (Chadronian

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...

) some 35 million years ago of North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 (Prothero, 2005).

It is the oldest rhino of which a well-preserved skeleton

Skeleton

The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...

 has been found. Trigonias was about 2.5 m (8 ft 2 in) long and, despite lacking horn

Horn (anatomy)

A horn is a pointed projection of the skin on the head of various animals, consisting of a covering of horn surrounding a core of living bone. True horns are found mainly among the ruminant artiodactyls, in the families Antilocapridae and Bovidae...

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 vestigal.