A new Squaloziphiid-like Odontocete (Mammalia: Cetacea) from Patagonia expands the Early Miocene diversity in the southwestern Atlantic Ocean

GAETÁN, CARLOS MAXIMILIANO; PAOLUCCI, FLORENCIA; BUONO, MÓNICA ROMINA

Trelew

Jornada; XXXV Jornadas Argentinas de Paleontología de Vertebrados; 2022

Neogene was a time of important ecological and taxonomic diversification for toothed whales or odontocetes, when most of the modern fauna was established. At the start of the Neogene (i.e. early Miocene), some groups of odontocetes achieved a great morphological and ecological diversification, however the fossil record for this time is scarce. The early Miocene marine (Gaiman Formation) sediments from Patagonia (Argentina) are worldwide known for preserving a rich assemblage of odontocetes, including platanistoids, physeteroids, kentriodontids and eurhinodelphinids. In the last decades, the early Miocene marine outcrops have been the focus of many new cetacean discoveries, expanding our knowledge of the radiation of crown odontocetes. In this work, we describe a toothed whale from Gaiman Formation (MPEF 1362; Estancia El crisol, Chubut province), and analyze its phylogenetic relationships. The specimen represents a small to medium size odontocete (270 to 315 cm of total length) and is represented by an incomplete skull, lacking the rostrum, ear bones and lacrimojugal. The anatomical and taxonomic analyses showed that this specimen cannot be referred to any already known species and is characterized by a unique combination of character among which are: premaxillae joining medially in the mesorostral groove, a slit-like external auditory meatus, presence of premaxillary crests and very narrow external bony nares. Thus, a new genus and species is proposed. The phylogenetic analyses recovered MPEF 1362 in the stem group of Delphinidae + Ziphidae + Physeteroidea, closely related to Northern Hemisphere species (e.g. Yaquinacetus, Squaloziphius). This new taxon highlights the importance of the Miocene marine sediments from Patagonia, and expands the paleobiogeographic distribution of squaloziphids- like forms to the Southwestern Atlantic Ocean.