Late Neogene (Late Hemphillian) rodents from the Pipe Creek Sinkhole, Grant County, Indiana

Abstract

ABSTRACT Spermophilus cf. howelli, Spermophilus sp., Castor or Dipoides sp., Geomys cf. adamsi, Symmetrodontomys daamsi, sp. nov., Bensonomys hershkovitzi, sp. nov., Ogmodontomys pipecreekensis, sp. nov., and Pliophenacomys koenigswaldi n. sp. are reported from the Pipe Creek Sinkhole of Grant County, Indiana. The Geomys sample demonstrates a variable sulcus morphology of the upper incisor, suggesting it stands near the Geomys—Pappogeomys boundary. Symmetrodontomys daamsi is characterized by its short lower molars and small mandible. Bensonomys hershkovitzi has a unique ml, with an anteroconid that with little wear connects deeply with the labial cingulum, and a mesolophid. O. pipecreekensis, with relatively low dentine tracts and no enamel atoll on ml, may be related to both Ogmodontomys sawrockensis and Ogmodontomys poaphagus, although it is probably not ancestral to either of them. Ogmodontomys Hibbard is considered an endemic North American genus distinguished from Mimomys Forsyth Major on the basis of a suite of dental features, including absence of a full lamellar enamel layer on leading edges of the molar triangles. The dentition of Pliophenacomys koenigswaldi exhibits a set of features suggesting a close relationship with Pliophenacomys finneyi of the early Blancan Fox Canyon local fauna of Kansas. Together with the rhinoceros Teleoceras, the rodent assemblage collectively suggests an early Pliocene (latest Hemphillian) age for the Pipe Creek biota. This is the first report of a late Neogene rodent fauna from Indiana.