An analysis of a new fossil of the extinct walrus Pelagiarctos suggests a different hypothesis to an earlier one that a "killer walrus" existed, preying on other marine mammals and/or birds, the researchers said.
The first fossils of Pelagiarctos, discovered in the 1980s, suggested a large, robust size of the jaw bone and sharp pointed cusps on the teeth similar to modern bone-cracking carnivores like hyenas, leading to the hypothesis it fed upon other marine mammals rather than the typical diet of fish as in modern walruses.
However, researchers from the University of Otago in New Zealand and the University of Wyoming said the new fossil, a lower jaw with teeth that was more complete than the original find, suggests Pelagiarctos was more of a fish eater, as it lacked adaptations for being a "killer walrus."
"This new find indicates that this enigmatic walrus would have appeared similar in life to modern sea lions, with a deep snout and large canines," Otago researcher Robert Boessenecker said.
Pelagiarctos is estimated to have been similar in size to some modern male sea lions, weighing close to 800 pounds.
"However, modern pinnipeds (seals, sea lions, and walruses) of small and large body sizes are dietary generalists, and tend to have diets rich in fish -- including sea lions similar in body size to Pelagiarctos, which means that its large body size alone doesn't make Pelagiarctos an apex predator," Boessenecker said.