Multituberculate mammals from near the Early-Late Cretaceous boundary, Cedar Mountain Formation, Utah

Herein we describe the oldest well-sampled multituberculate assemblage from the Cretaceous of North America. The fauna is dated at 98.37 Ma and thus a pproximates the Albian-Cenomanian (Early-Late Cretaceous) boundary. The mul tituberculate fauna is diverse. Two of the multituberculates (Janumys erebo s gen. et sp. n. and an unidentified taxon) are provisionally placed among 'Plagiaulacida'. Another taxon, Ameribaatar zofiae gen. et sp. n., is of un certain subordinal affinities. The remaining multituberculates appear to re present the advanced suborder Cimolodonta and fall within the 'Paracimexomy s group'. We rediagnose Paracimexomys on the basis of the type species, P. priscus, and refer to other species as cf. Paracimexomys (including cf. P. perplexus sp. n.). A revised diagnosis is also provided for Cenomanian Dako tamys. A previously-described species from the Cedar Mountain Formation is placed in Cedaromys gen. n. as C. bestia, together with C. parvus sp. n. Br yceomys is represented in the fauna by B. intermedius sp. n. Relationships of Paracimexomys-group to later taxa remain obscure. However, Bryceomys and Cedaromys share a number of features with Cimolodontidae. Given these rese mblances, together with the fact that Cimolodontidae retain certain plesiom orphies (stout lower incisor, gigantoprismatic enamel) with respect to Ptil odontoidea (to which they are commonly referred), we suggest that Cimolodon tidae may have arisen from a clade within the 'Paracimexomys group', indepe ndent of ptilodontoids.