A Pliocene?Pleistocene continental biota from Venezuela

CARRILLO-BRICEÑO,J.D.; SÁNCHEZ R.; SCHEYER, TORSTEN M.; CARRILLO, JUAN D.; DELFINO M.; GIORGIOS G; KREBER L.; CARLINI A.A.; SÁNCHEZ VILLAGRA M.

Swiss Journal of Palaeontology

Springer Open

Lugar: Zurich; Año: 2021 vol. 140 p. 1 - 76

1664-2376

A Pliocene?Pleistocene continental biota from VenezuelaJorge D. Carrillo‑Briceño* , Rodolfo Sánchez, Torsten M. Scheyer , Juan D. Carrillo,Massimo Delfino, Georgios L. Georgalis, Leonardo Kerber, Damián Ruiz‑Ramoni, José L. O. Birindelli,Edwin‑Alberto Cadena, Aldo F. Rincón , Martin Chavez‑Hoffmeister, Alfredo A. Carlini,Mónica R. Carvalho, Raúl Trejos‑Tamayo, Felipe Vallejo, Carlos Jaramillo, Douglas S. Jones andMarcelo R. Sánchez‑Villagra*AbstractThe Pliocene?Pleistocene transition in the Neotropics is poorly understood despite the major climatic changes thatoccurred at the onset of the Quaternary. The San Gregorio Formation, the younger unit of the Urumaco Sequence,preserves a fauna that documents this critical transition. We report stingrays, freshwater bony fishes, amphibians,crocodiles, lizards, snakes, aquatic and terrestrial turtles, and mammals. A total of 49 taxa are reported from the VergelMember (late Pliocene) and nine taxa from the Cocuiza Member (Early Pleistocene), with 28 and 18 taxa reportedfor the first time in the Urumaco sequence and Venezuela, respectively. Our findings include the first fossil record ofthe freshwater fishes Megaleporinus, Schizodon, Amblydoras, Scorpiodoras, and the pipesnake Anilius scytale, all fromPliocene strata. The late Pliocene and Early Pleistocene ages proposed here for the Vergel and Cocuiza members,respectively, are supported by their stratigraphic position, palynology, nannoplankton, and 86Sr/88Sr dating. Mammalsfrom the Vergel Member are associated with the first major pulse of the Great American Biotic Interchange. In contrastto the dry conditions prevailing today, the San Gregorio Formation documents mixed open grassland/forest areas surroundingpermanent freshwater systems, following the isolation of the northern South American basin from westernAmazonia. These findings support the hypothesis that range contraction of many taxa to their current distribution innorthern South America occurred rapidly during at least the last 1.5 million years.