A simplicidentate mammal, Hanomys malcolmi, new genus and species, is the only fossil currently known from a recently discovered, presumably Paleocene, locality near Danjiangkou, Hubei Province, China. The specimen consists of the anterior part of a skull with complete dentition and articulated lower jaw, lacking only P₃. Hanomys resembles the mixodont simplicidentates Heomys and Eurymylus in dental formula and general morphology of the cheek teeth. It differs from them in a combination of characters such as a more expanded hypocone on P⁴–M² and dorsoventral expansion of the anterior root of the zygomatic arch. These characters indicate that Hanomys is at the root of the clade that includes Rhombomylus and Matutinia. This clade, a short-lived lineage known only from Asia, is here recognized as the family Rhombomylidae.