What is "trigonias"

Trigonias is an extinct genus of rhinoceros from the late Eocene ( Chadronian) some 35 million years ago of North America (Prothero, 2005). It is the oldest rhino of which is still alive. Trigonias was about 2.1 m (7 ft) long and, despite lacking horns, 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.

A specimen of T. osborni was estimated to have a weight of about 391.4 kg (862.9 lbs).