Discovered in what is now North Dakota by archeologists in 1982, the Eoarctos vorax was a raccoon-sized bear that lived about 30 million years ago. The creature was an early arctoid, the same type of mammals that bears are. Eoarctos was one of the earliest mammals capable of crushing hard objects because of its teeth. Eoarctos probably used its teeth to eat the shellfish living in prehistoric North Dakota rivers. However, possibly because of its shellfish diet, the animal had broken teeth on both sides of its mouth. The teeth were broken off their roots and badly infected.

Prior to this discovery, archaeologists had thought that arctoids evolved in what is now Europe. Even though this Eoarctos vorax lived a short and painful life, they definitely helped us understand early mammal evolution much better than before.