2.2" Fossil Squirrel-Like Mammal (Ischyromys) Skull - Wyoming

Fossil Squirrel-Like Mammal (Ischyromys) Skull - Wyoming #197366

This is a 2.2" long skull and a 1.65" long jaw (left mandible) of Ischyromys typus, a squirrel/mouse-like mammal. It was collected from the the White River Formation in Converse County, Wyoming and would be approximately 30-34 million years old. The skull and left mandible have been exposed from the rock in a unique fashion that creates quite an aesthetic display that doesn't require an acrylic display stand.

There is a repaired crack through the skull where the rock broke during collection, and there are repaired cracks through the incisor. However, this specimen required no restoration which is quite incredible for a skull of this size.

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.