Zapus

Zapus is a genus of North American jumping mouse. It is the only genus whose members have the dental formula 1.0.1.31.0.0.3. Zapus are the only extant mammals aside from the Aye-aye with a total of 18 teeth. This genus was first separated from Old World jerboas by Coues in 1875. Members of this genus are very similar in appearance, all species having long tails, long hind feet and yellowish-brown pelage above and white below, the colors distinctly separated by a yellowish-orange lateral line. The genus contains three extant species: A number of fossil species are also known, with the oldest being Zapus rinkeri from the Blancan of Kansas.