Original article A new Miocene vertebrate assemblage from the Rı ´o Yuca Formation (Venezuela) and the northernmost record of typical Miocene mammals of high latitude (Patagonian) affinities in South America § Ascanio D. Rinco ´n a, *, Andre ´s Solo ´ rzano a , Oliver Macsotay b , H. Gregory McDonald c , Mo ´ nica Nu ´n ˜ ez-Flores a a Instituto Venezolano de Investigaciones Cientı´ficas (IVIC), Laboratorio de Paleontologı´a–Centro de Ecologı´a, Km 11 de la Carretera Panamericana, Edo. Miranda. Aptdo. 21.827, 1020-A Caracas, Venezuela b Urbanizacio ´n Trigal Norte, Avenida Atla ´ntico, 155-61B Valencia, Estado Carabobo, Venezuela c Bureau of Land Management, Utah State Office, 440 West 200 South, Salt Lake City, UT 84101, USA 1. Introduction The modern South American (SA) neotropics harbor some of the most species-rich terrestrial ecosystems in the world. This present- day biodiversity is the result of a long evolutionary history of extreme complexity in terms of tectonic activity and changing environmental conditions, as exemplified by the outstanding fossil records contained in some Neotropical Miocene formations (Kay et al., 1997; Myers et al., 2000; Croft, 2007; Sa ´ nchez-Villagra et al., 2010; Hoorn et al., 2010; Tejada-Lara et al., 2015; Antoine et al., 2016). Molecular data indicate the origin of several clades of modern neotropical plants and animals by the Middle to Late Miocene, but from the northernmost portions of SA (a wide area with a high level of modern biodiversity), there are only a few well- known continental vertebrate assemblages of this age (e.g., Hoorn et al., 2010; Tejada-Lara et al., 2015; Moreno et al., 2015). Among these, the widely sampled and better studied faunas come from La Venta (Middle Miocene, Colombia; Kay et al., 1997) and the Urumaco sequence (Middle to Late Miocene, Venezuela; Sa ´ nchez- Villagra et al., 2010). The recent discoveries of continental Geobios 49 (2016) 395–405 A R T I C L E I N F O Article history: Received 18 September 2015 Accepted 13 June 2016 Available online 5 August 2016 Keywords: Nesodontinae Peltephilidae Pimelodidae Middle to Late Miocene Venezuela South America A B S T R A C T Geological explorations of the basal beds of the Rı ´o Yuca Formation (Tucupido region, Portuguesa State, western Venezuela) resulted in the recognition of a new vertebrate assemblage that includes eight taxa: the toxodont cf. Adinotherium, a Peltephilidae armadillo, the freshwaters fishes Platysilurus and Phractocephalus, the caiman Purussaurus, an indeterminate dolphin, turtles, and the previously recognized sloth Pseudoprepotherium venezuelanum. When compared with the higher latitudes faunas of Argentina and Chile, the presence of cf. Adinotherium and peltephilids in the Rio Yuca Formation is consistent, but not conclusive, with a Santacrucian to Frisian SALMA age. The associated fauna, as well recent apatite fission track analysis, indicates that the Rı ´o Yuca assemblage is more likely younger in age, specifically Middle to Late Miocene. So far, the Miocene localities of the northern part of South America have provided a less prolific fossil record compared to the southern part of the continent (e.g., Santacrucian and Friasian faunas of Patagonia), but the present work documents the surprising occurrence of two taxa (Peltephilidae and Nesodontinae) common in southern high latitude faunas of South America, implying the persistence of the Santacrucian-Friasian genus Adinotherium in younger strata from northern South America, and that peltephilids were much more widespread during the Miocene than previously recognized. The presence of these common Patagonian taxa (Peltephilidae and Nesodontinae) in Rı ´o Yuca also supports the hypothesis of prior researchers for the existence of biogeographical connections between the northern and southern portions of South America during the Late Oligocene or Early Miocene, which facilitated faunal interchange between the two regions. Finally, the biogeographical affinities of the freshwater fishes and the giant caiman (Purussaurus) indicate close relationships of the Tucupido region with the ancestral distribution of the Orinocoan–Amazonian drainage system. ß 2016 Elsevier Masson SAS. All rights reserved. § Corresponding editor: Pierre-Olivier Antoine. * Corresponding author. E-mail address: paleosur1974@gmail.com (A.D. Rinco ´ n). Available online at ScienceDirect www.sciencedirect.com http://dx.doi.org/10.1016/j.geobios.2016.06.005 0016-6995/ß 2016 Elsevier Masson SAS. All rights reserved.