C is for Colodon.
The genus Colodon made its first appearance in the Uintan. It is a type of hooved mammal most closely related to modern tapirs.
You can read more about Colodon here:
Colbert, 2005, The Facial Skeleton of the Early Oligocene Colodon (Perissodactyla, Tapiroidea): Palaeontologia Electronica, v. 8.