The earliest Neogene vertebrate assemblage of the Pisco Basin, Peru

We describe a new elasmobranch assemblage collected from phosphorite layers exposed at Cerro Tiza, in the Ica River valley (Eastern Pisco Basin, southern Peru). Chronostratigraphic and biostratigraphic data indicate an Aquitanian (Lower Miocene) age and support attribution of these strata to the Tunga Formation, thereby identifying this record as the geologically oldest Neogene vertebrate assemblage so far documented from the Pisco Basin. The assemblage comprises at least 17 species and 15 genera of selachians and batoids referable to the orders Lamniformes, Carcharhiniformes and Myliobatiformes. These taxa document a diverse marine ecosystem dominated by apex and mesopredatory species with predominantly piscivorous feeding habits, consistent with environmental conditions of elevated primary productivity. Taphonomic and paleoecological evidence indicates that the apparent dominance of a limited number of species within the Early Miocene Tunga phosphorite lag likely reflects the combined effect of both ecological structure and taphonomic filtering.