Anchitheriomys buceei (Rodentia, Castoridae) from the Miocene of Texas and a review of the Miocene beavers from the Texas Coastal Plain, USA

Abstract

The record of fossil beavers from Miocene age strata in the Texas Coastal Plain is sparse. The first occurrence of fossil beavers is in Arikareean age faunas. One fossil beaver specimen was reported from a Hemingfordian fauna near Navasota, TX. Both Monosaulax and Anchitheriomys are described here from multiple early Barstovian faunas including a new taxon, Anchitheriomys buceei. The taxon, A. buceei, was a relatively large beaver, similar to A. fluminis in size, and shares characters with both A. fluminis and A. nanus. The holotype of Anchitheriomys buceei is a partial skull and endocast that preserves key features of the orbital foramina and palatine. Referred specimens include a partial dentary, isolated cheek teeth, and two post-cranial elements. The co-occurrence of this taxon and a small beaver identified as Monosaulax sp. in early Barstovian faunas is coeval with the first occurrence of proboscideans along the Texas Coastal Plain. Beavers are unknown in late Barstovian and Clarendonian faunas, although rodent fossils are uncommon from these faunas in general. Most of the fossil beaver specimens were obtained in the early twentieth century by collectors affiliated with Dr. Mark Francis at Texas A&M University, or with the State-Wide Paleontologic-Mineralogic Survey in Texas and are curated at the Texas Vertebrate Paleontology Collections. Archival materials housed at that facility have been instrumental in unraveling the history of collection, the distribution of localities and the evolving understanding of Miocene vertebrate biostratigraphy on the Texas Coastal Plain.