Deep time dietary convergence evidenced by the stomach contents of a fossil seal from the Southwest Atlantic.

The Neogene fossil record of Patagonia provides important insights into the evolution and ecological diversification of marine predators in the Southern Hemisphere. Among these, Kawas benegasorum, an extinct seal from the Late Miocene Puerto Madryn Formation, represents the only record of a putative phocine (northern seals) in the Southern Hemisphere and preserves rare evidence of stomach contents. However, its original description was concise, and lacked detailed information on its dentition and stomach contents, leaving aspects of its morphology, phylogeny and paleoecology unresolved. We re-describe the holotype and only known specimen of K. benegasorum, providing the first comprehensive study of its postcranial morphology, new information on its dentition and a detailed examination of its stomach contents. We show that Kawas has both monachine- and phocine-like traits, with an overall morphology suggesting affinities with Monachinae. However, phylogenetic analyses yielded conflicting results, recovering Kawas either within Phocinae or in an unresolved position within Phocidae. The stomach contents indicate a piscivorous diet with coastal, benthic and demersal prey, broadly comparable to that of extant South American sea lions inhabiting the region. These results document early benthic nearshore foraging in pinnipeds and suggest dietary convergence across geological time in the western South Atlantic by the Late Miocene.