Phylogeny, systematics, and evolution of hypsodonty in the Aplodontiinae (Mammalia, Rodentia, Aplodontiidae), with the description of several new species

ABSTRACT

Whereas aplodontiid rodents are represented today by a single living species, their fossil record is diverse in number of species (>100), in morphology, and in ecology. Recent phylogenetic efforts are beginning to make sense of the relationships among diverse members of the clade, but there is still much to learn about the relationships within the morphologically coherent subfamilies of this large group. The subfamily Aplodontiinae, including the extant Aplodontia, ranges from the mid-Miocene through recent, including only eight described species. This is the least diverse clade of aplodontiids, even though it is the only extant group. This study describes three new species, increasing the diversity of described fossil aplodontiids by more than a third. The description herein of Liodontia bathypotamos, n. sp., from the late Hemingfordian of Montana, Liodontia dailyi, n. sp., from the late Hemingfordian of Nevada, and Aplodontia minor, n. sp., from the late Hemphillian of Oregon extends the geographic and temporal range of the subfamily. A phylogenetic analysis of all known aplodontiines finds support for slow diversification and possible anagenetic change within lineages while also suggesting substantial missing time in the aplodontiine fossil record. However, the morphological changes, including rapid increases in hypsodonty, along the aplodontiine lineage yield an extant species, Aplodontia rufa, that, despite its early divergence from the rest of crown group Rodentia, is not at all representative of the ‘primitive’ rodent it is commonly assumed to be.

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ERRATUM: Phylogeny, systematics, and evolution of hypsodonty in the Aplodontiinae (Mammalia, Rodentia, Aplodontiidae), with the description of several new species

ACKNOWLEDGMENTS

I would like to thank M. J. Morea for kindly allowing me to describe a species originally delineated in his dissertation on the Massacre Lake Fauna. J. O. R. Ebbestad (Uppsala University Museum), P. Holroyd (UCMP), A. Henrici (CMNH), and N. Pyenson (USNM) kindly provided photographs of specimens from their collections. P. Holroyd (UCMP), R. Eng (UWBM), and E. Davis (UOMNH), who helped me visit collections, curate and borrow specimens of some of the species described here. R. Hunt kindly provided a cast of Sewelleladon that helped with early versions of the phylogenetic analyses presented here. I thank J. Calede for sharing a specimen from Flint Creek in his dissertation material, cataloging it, and helping to place it in geological context. Qiu Z. (IVPP) provided information about unpublished Asian specimens. L. Flynn and an anonymous reviewer provided helpful feedback on an earlier draft of the manuscript. Members of the Hopkins laboratory read various drafts.