New material of the Oligocene muroid rodent Nonomys, and its bearing on muroid origins. American Museum novitates ; no. 2712

Abstract

"New material shows that Nonomys simplicidens has the dental formula, and some of the dental characters, of the Cricetidae. These are combined with an hystricomorphous zygomasseteric structure like that in Dipodoidea, i.e., the enlarged foramen for the medial masseter is separated by a lamina of bone from a smaller foramen which transmits the infraorbital nerve and blood vessels, and there is virtually no development of a zygomatic plate. This ambiguous combination of characters is seen also in late Eocene Simimys, which has been classified as a dipodoid and as a muroid. Nonomys and Simimys are interpreted as members of an early radiation of myodont rodents, with derived characters that place them in the Muroidea rather than Dipodoidea, but with a combination of characters that excludes them from any presently defined family"--P. [1].