Scientists have published a detailed new description of what they call Argentina’s most complete fossil seal, a roughly 10-million-year-old skeleton from Península Valdés whose stomach contents show it ate coastal, bottom-dwelling fish, broadly like today’s sea lions.
The animal, Kawas benegasorum, lived between about 10 and 9 million years ago, when the part of Chubut province that is now Península Valdés, a peninsula on Patagonia’s Atlantic coast, lay under a shallow sea. The skeleton was found in the 1990s at Punta San Román and given a short description in 2001; its teeth and stomach contents had not been studied in detail. It is kept at the Egidio Feruglio Paleontological Museum in Trelew.
The study, published in the journal Royal Society Open Science, was led by Ana Valenzuela-Toro of a paleontology research center in Chile. The other authors, including Felipe Busker, are researchers in Puerto Madryn with Conicet, Argentina’s national research council.
In the animal’s abdomen the team found bones consistent with three groups of fish: flatfishes, bass-like or scorpionfish-like species, and cod-like fish including hake. The 2001 description had reported an angel shark among the remains, but the team identified no angel-shark remains. Most of the material is half-digested bone fragments, Busker said, so the fish can often be identified only to family level.
These fish lived on or near the sea floor of the continental shelf, which the paper says points to a diet comparable to that of South American sea lions today. Busker said the diet was “very similar” to that of sea lions and male elephant seals in the area now. The paper says this likely reflects dietary convergence, similar feeding habits arising in animals that are not close relatives.
The paper cautions that the bones probably show only part of what Kawas ate, since soft-bodied prey such as squid would rarely survive as fossils, and that the evidence does not rule out feeding farther offshore.
Kawas was about 1.9 to 2.2 meters long, the paper estimates, the size of a young male or adult female sea lion. Its bones and teeth mix traits of the two main seal groups, the northern seals and the mostly southern ones, and the skeleton has no skull, which the researchers say makes its relatives hard to pin down. Only three fossil seal records are known in Argentina, Busker said, and Kawas is by far the most complete.