Wikipedia
Dakotamys
Dakotamys is a genus of extinct mammal that lived during the Upper Cretaceous. It shared the world with dinosaurs. This small creature was a member of the also extinct order Multituberculata within the suborder Cimolodonta and was a member of the Paracimexomys group.
The genus Dakotamys ("Dakota mouse") was named by Eaton J.G. in 1995. Dakota refers to the Dakota Formation. It's a geological term rather than a geographical one. " Paracimexomys and Dakotamys... resemble the Eobaataridae in the structure of the upper and lower molars, with cusps showing a tendency to coalesce, and with ornamentation of grooves and ribs on the molars," (Kielan-Jaworowska & Hurum, 2001, p.403).