Fossil snakes (Squamata, Serpentes) from the tar pits of Venezuela: taxonomic, palaeoenvironmental, and palaeobiogeographical implications for the North of South America during the Cenozoic/Quaternary boundary

PeerJ. 2018 Aug 14:6:e5402. doi: 10.7717/peerj.5402. eCollection 2018.

Abstract

Background: Tar seep deposits in South America historically are well-known for their rich record of fossil mammals, contrasting with only a few formal reports of reptile remains. Here we report a new snake fauna recovered from two tar pits from Venezuela. The fossil remains come from two localities: (a) El Breal de Orocual, which comprises an inactive tar seep estimated to be Plio/Pleistocene in age; and (b) Mene de Inciarte, an active surface asphalt deposit with an absolute age dating to the late Pleistocene.

Methods: The taxonomic identity of all specimens was assessed via consultation of the relevant literature and comparison with extant specimens. The taxonomic assignments are supported by detailed anatomical description.

Results: The Mene de Inciarte snake fauna comprises vertebral remains identified as the genus Epicrates sp. (Boidae), indeterminate viperids, and several isolated vertebrae attributable to "Colubridae" (Colubroidea, sensu Zaher et al., 2009). Amongst the vertebral assemblage at El Breal de Orocual, one specimen is assigned to the genus Corallus sp. (Boidae), another to cf. Micrurus (Elapidae), and several others to "Colubrids" (Colubroides, sensu Zaher et al., 2009) and the Viperidae family.

Conclusions: These new records provide valuable insight into the diversity of snakes in the north of South America during the Neogene/Quaternary boundary. The snake fauna of El Breal de Orocual and Mene de Inciarte demonstrates the presence of Boidae, Viperidae, "colubrids", and the oldest South American record of Elapidae. The presence of Corallus, Epicrates, and viperids corroborates the mosaic palaeoenvironmental conditions of El Breal de Orocual. The presence of Colubroides within both deposits sheds light on the palaeobiogeographical pattern of caenophidians snake colonization of South America and is consistent with the hypothesis of two episodes of dispersion of Colubroides to the continent.

Keywords: Boidae; Colubroidea; Elapidae; Fossils snakes; Micrurus; Palaebiogeography; Panama Isthmus; South America; Venezuela.

Grants and funding

This research was funded by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Richard Gilder Graduate School of American Museum of Natural History (AMNH), Collection Study Grants (grant to Silvio Onary), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq Proc. n. 309434/2015-7 for Annie S. Hsiou), Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP, Process n. 2011/14080-0 for Annie S. Hsiou and Process n. 2017/00845-1 for Silvio Onary), the Venezuelan Education University, Science, and Technology Ministry (grant to Ascanio D. Rincón IVIC-1096, Venezuelan PaleoMapas); the Petróleos de Venezuela S.A. (PDVSA), and Instituto de Patrimonio Cultural, Venezuela. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.