The largest freshwater odontocete: A South Asian river dolphin relative from the proto-Amazonia.

Abstract

Several dolphin lineages have independently invaded freshwater systems. Among these, the evolution of the South Asian river dolphin <i>Platanista</i> and its relatives (Platanistidae) remains virtually unknown as fossils are scarce. Here, we describe <i>Pebanista yacuruna</i> gen. et sp. nov., a dolphin from the Miocene proto-Amazonia of Peru, recovered in phylogenies as the closest relative of <i>Platanista</i>. Morphological characters such as an elongated rostrum and large supraorbital crests, along with ecological interpretations, indicate that this odontocete was fully adapted to fresh waters. <i>Pebanista</i> constitutes the largest freshwater odontocete known, with an estimated body length of 3 meters, highlighting the ample resource availability and biotic diversity in the region, during the Early to Middle Miocene. The finding of <i>Pebanista</i> in proto-Amazonian layers attests that platanistids ventured into freshwater ecosystems not only in South Asia but also in South America, before the modern Amazon River dolphin, during a crucial moment for the Amazonian evolution.