Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5-12 Ma) of North America

The Penny Creek Local Fauna in southern Webster County, Nebraska, is an early Clarendonian fossil locality within the Ash Hollow Formation. Undescribed fossils from previously collected Penny Creek material represent the first record of snakes from this time interval and confirm the presence of multiple taxa immediately following the Mid Miocene Climatic Optimum. We identified eight taxa from the locality, including one booid (Charina), three colubrines (Pantherophis, Lampropeltis, and Salvadora), a dipsadid (Heterodon/Paleoheterodon), and several natricids (Neonatrix elongata, Neonatrix magna, and Nerodia). Of these snakes, only Neonatrix is an extinct genus, Charina and Salvadora are presently extirpated from the area, and all other genera are represented in the Central Great Plains today. Habitats occupied by extant members of genera represented in the Penny Creek snake assemblage suggest a relatively open environment with loose substrates and plentiful ground cover near a permanent water source. This further corroborates previous geological and mammalian paleoecological assessments of the Penny Creek area as a somewhat open, woodland-prairie ecotone environment near a permanent, high-energy fluvial water source. Finally, the snakes of Penny Creek help contribute to our understanding of the modernization of North American snake assemblages in the Central Great Plains by providing data for a poorly understood time within the evolution of North American snakes