We explored a part of the rock sequence in the late Miocene age deposits of northern Pakistan that hitherto had yielded few fossil vertebrates and almost no rodents. A particularly rich site dating to 11.1 Ma was identified and sampled for small mammals. In the rich assemblage was an unusual new rodent – an end member of an extinct lineage without close living relatives. This diatomyid rodent, Willmus maximus, a previously unknown species, is obviously special based on morphology of the teeth, but only two teeth among >300 represent it. This species, unlike earlier ones, is rare, specialized, and young in geological age. The next oldest diatomyid rodents are from the early Miocene. We do not know what the occurrence of Willmus means with respect to ecology or geographic range, but we can rule out some possibilities. For example, its record is not a reflection of a peculiar habitat, because species composition of its locality is similar to that of both preceding and succeeding faunas. Possibly the specialized nature of the species was a factor in its preservation.
Miocene: period of geological time spanning approximately 25 to 5 million years ago.
Diatomyid: group of rodents; an extinct family that is perhaps closest to the African gundi among living rodents.