- Ischyromys (Squirrel-Like Rodent)
- Oligocene Age
- Brule Formation
- South Dakota
- Specimen measures approx. 13/16″ long and comes in the 1.5″ Gem Jar
Ischyromys is an extinct genus of rodent from North America, often labeled as a Squirrel. It possessed strong hind limbs with claws on each five toes of its hind feet, like modern rodents. It is believed that Ischyromys was an efficient tree climber like squirrels today. These ancient rodents grew to about two feet (over half a meter) in length, and resembled large mice in appearance, but probably lived in trees like squirrels do today. While they are considered among the more primitive rodents, Ischyromys had large front teeth (called incisors) like the rodents we are familiar with today. Ischyromys is the most common Early Oligocene fossil rodent found in South Dakota, Nebraska, Wyoming and Colorado. It has also been found as far north as Saskatchewan, Canada and as far south as Texas. Ischyromys went extinct around 25 million years ago. The only living relative is the distantly related mountain beaver (Aplodontia rufa), a small rodent that now lives along the west coast of North America.