The Titanotheres (also known as brontotheres) are extinct family of large, rhinoceros-like mammals that were ancestors of the horse, rhinoceros, and tapir. Titanotheres had horn-like structures on their snout; bony knobs protruded from their skull and were covered with thick skin. Males had larger knobs than females. These herbivores ate soft forest vegetation and were up to 8 feet (2.5 m) tall at the shoulder. Titanotheres had a tiny brain, only as big as a fist. They had four hoofed toes on each front foot and three hoofed toes on each rear foot They lived from the early Eocene until the middle Oligocene (from 58-30 million years ago). Some Titanotheres include Brontops &, Brontotherium (both 8 ft tall, from North America), Dolichorhinus (4 ft tall, from North America), Eotitanops (1.5 ft tall, from North America and Asia), and Embolotherium (8 ft tall, from Mongolia).
The last photo is of the original fossil.