A new miniscule rodent represented by isolated cheek teeth is reported from the lower part of the late Early Eocene Arshanto Formation, Nuhetingboerhe (Camp Margetts) area, Inner Mongolia. A new family, based on the new genus and species, is proposed. The new taxon resembles alagomyids but differs from early rodents in having a partial buccal cingulum, a distinct metaconule that merges posteriorly with the postcingulum, a transversely oriented trigon basin that widely separates the paracone and

more »

... metacone, a prominent hypoconulid on lower molars, and in lacking the hypocone and protocristid. It differs from alagomyids in having a greater length/ width ratio of upper cheek teeth, a neomorphic cusp termed as the preprotoconule, a preprotoconule crista that projects anteriorly, an anteroconid on dp4, an oblique cristid obliqua bearing a distinct mesoconid, and the hypoconid more posteriorly extended (or hypoconulid less posteriorly extended) on m3. The dental morphology of the new taxon is derivable from an alagomyid dental pattern and is intermediate between alagomyids and rodents of modern aspect; it casts new light on the evolution of dentition of early rodents.