Fossil poop (Coprolite) – South Dakota
Oreodonts are extinct Artiodactylids (even-toed mammals) most closely related to camels and pigs, with no close relatives living today. All are herbivorous, browsing on a diet of leaves and young shoots.
Although tempting to think of them as feeding on “grass”, true grasses did not appear until the late Oligocene, evolving and expanding widely during the Miocene as savannahs appeared during the cooling and drying of the that epoch. Oreodonts fed on different types of vegetation than many modern artiodactylids do and therefore occupied an ecologically different niche than many living ungulates.