Fossil Squirrel-Like Mammal Jaws With Camelid Leg Bones - Wyoming

This 60 centimeter (2 foot) long creature is one of the oldest rodents known. It had a squirrel-like or mouse-like appearance and already had characteristic rodent incisors. Ischyromys's hind legs were longer than its forelegs, which could have been used for other means than walking. Unlike most other mammals of its time, Ischyromys was probably arboreal, primarily living in trees.

Poebrotherium (meaning "grass-eating beast") is an extinct camelid that roamed North America between the Eocene and Miocene epochs. They were smaller than modern camels, about the same size as a modern sheep, and fit in the place of deer or gazelles in the White River fauna. Despite their name, it is believed that grass was likely not their primary food source but they were instead browsers, feeding on various foliage and berries. Based on bite marks in bones, they were likely preyed on by Archaeotherium, an extinct boar-like entelodont which was also prevalent throughout the White River ecosystem.