Morphology and systematics of a new fossil snake from the early Rupelian (Oligocene) White River Formation, Wyoming

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Abstract
Extinct snake taxa are recognized primarily from isolated vertebrae. A new specimen from the early Oligocene of Wyoming provides a rare opportunity to examine four nearly complete and articulated fossil snakes. Informally assigned previously to the ‘erycine’ vertebral form taxa Ogmophis and Calamagras, a detailed comparison reveals that this fossil snake exhibits vertebral differences from both taxa and is, furthermore, a new taxon, Hibernophis breithaupti gen. et sp. nov., based on a combination of apomorphies such as absence of basal tubera, low subrectangular prootic, low parasphenoid wings obscuring the anterior opening of the Vidian canal, and foramen for the mandibular branch of the trigeminal nerve posteriorly displaced inside the adductor fossa of the compound. Parsimony and Bayesian phylogenetic analysis of combined morphological and molecular data from a broad selection of snakes places Hibernophis breithaupti as sister taxon to all other booids, distant from both Old and New World ‘erycines’. However, an alternative position close to New World ‘erycines’ and ungaliophiines cannot be rejected.
Funding Information
  • Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
  • Fundação de Amparo à Pesquisa do Estado de São Paulo (850 2017/00845-1)
  • Fundação de Amparo à Pesquisa do Estado de São Paulo (2019/11166-3)
  • Australian Research Council (DP200102328)

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