U is for Uintatherium
Uintatherium was a massive hoofed mammal that lived during the Eocene epoch. Superficially, they were rather rhinoceros-like, though they were not related.
A reconstruction of Uintatherium.
Credit: Dmitry Bogdanov CC 3.0 By SA
Notably, Uintatheres had many horns and protuberances on their skulls, in addition to robust tusks.
Cast of Uintatherium anceps (Leidy, 1872) – syn. Dinoceras mirabile (Marsh 1872) skull, neck vertebrae.
Credit: Jebulon [Public Domain]