An Early Neogene Elasmobranch fauna from the southern Caribbean (Western Venezuela)

Abstract

The Cantaure Formation (Burdigalian to ?early Langhian) is located in the Falcon Basin, North Western Venezuela, and includes one of the most diverse Neogene teleostean and benthonic invertebrate faunas in Tropical America. The paleoenvironmental preferences of the members of this fauna, as well as published paleogeographic reconstructions, suggest that the Cantaure Formation was deposited in a highly-productive shallow water environment, associated with coastal upwelling. We documented a paleodiversity of 39 shark and ray species, including 15 previously unreported taxa for Venezuela and six for Tropical America. We performed a bathymetric analysis of the fossil assemblage based on the distribution of closely-related extant chondrichthyan relatives of fossil taxa and discuss the ecological role and stratigraphic significance of the latter. Our results support the hypothesis that the Cantaure Formation was deposited in an insular inner-middle shelf environment. The elasmobranch fauna is characterized by a predominance of benthopelagic sharks with piscivorous feeding preferences (e.g., †Paratodus, Galeorhinus, Hemipristis, Rhizoprionodon, Carcharhinus, Isogomphodon, Negaprion, †Physogaleus and Sphyrna) followed by durophagous/cancritrophic feeders (e.g., Heterodontus, Nebrius, Mustelus, Rhynchobatus, Pristis, Dasyatis, cf. Pteroplatytrygon, cf. Taeniurops, Aetobatus, Aetomylaeus and Rhinoptera). Filter (e.g., Mobula and †Plinthicus), eurytrophic/sarcophagous (e.g., †Carcharocles and Galeocerdo) and teuthitrophic (e.g., Alopias) feeder species were also found. Teeth of Carcharocles megalodon found in Burdigalian sediments of the Cantaure Formation support the presence of this species already in the early Miocene. Some taxa (Nebrius, Carcharhinus cf. C. macloti and Rhynchobatus) are absent from the extant Caribbean and Western Atlantic fauna, but were present in the region before the closure of the Central American Seaway.