The Heteroymyids are a group of distinctive rodents that share the characteristics
of having external furlined cheek pouches (like the pocket gophers) and light
bone structure in the skull. They also have enlarged back legs and feet, an
evolutionary trend toward bipedal locomotion (walking on two feet). Members
of this group that can be found in North Dakota include the olive-backed pocket
mouse, plains mouse, and the Ord's kangaroo rat.