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).