A new vertebrate continental assemblage from the Tortonian of Venezuela

A wide variety of aquatic vertebrates from fluvio-lacustrine facies of northern South America (Colombia and Venezuela) have been used as unequivocal evidence to support hydrographic connections between western Amazonia and the Proto-Caribbean Sea during the Miocene. By the end of the Miocene, changes in the major hydrographic systems of the region produced losses of habitats and a regional faunal turnover, as has been documented in the geological record of the Urumaco region. Here, we report a new Tortonian aquatic and terrestrial vertebrate assemblage from two localities of the Caujarao Formation (El Muaco Member) in western Venezuela. The vertebrate assemblage includes a gharial (cf. Gryposuchus pachakamue), alligatorid crocodylians (Purussaurus and Alligatoridae indet.), a freshwater turtle (Chelus sp.), snakes (cf. Eunectes sp.), serrasalmids and pimelodids and thorny catfishes, a rodent (Potamarchus sp.), pampatheres (Scirrotherium sp.), sloths, as well as plant remains (coal and amber). Although the Caujarao Formation has been referred to as a fully marine environment, the new assemblage reported here suggests a freshwater input to the coastal area. Taxonomic and biogeographic affinities between the Muaco Member community and that reported from the Miocene proto-Amazonian systems are indicative of the persistence of ecological and hydrographic continuity at minimum until the end of the Miocene in at least an area of northwestern South America. Keywords Neogene Miocene Caujarao Formation Orinoco River Biogeograph