illustration of two dolphins
Robert Boessenecker

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This ancient dwarf dolphin may have slurped its food like a walrus

You’d think a “toothed whale” would have teeth. But scientists examining the 30-million-year-old partial skulls of two dwarf dolphins found that not only were they missing their pearly whites, but the snub-nosed cetaceans likely slurped up their prey from the seafloor. The paleontologists who analyzed two partial skulls found in South Carolina—one recently discovered by a diver and the other unearthed from the same formation more than 30 years ago—put the long-extinct creature in a new genus dubbed Inermorostrum, which roughly translated from Latin means “defenseless snout.” Larger-than-normal holes that once carried blood vessels and nerves through the bones of the snout suggest the dolphin had enlarged lips needed to feed via suction, the researchers report today in the Proceedings of the Royal Society B. The marine mammal may even have had short, walrus-like whiskers to better sense prey while grubbing through seafloor sediments, the researchers speculate. Likely measuring between 1.2- and 1.5-meters long, the dolphin was about the same size as today’s vaquita, the world’s smallest and most endangered cetacean, and it likely foraged in shallow, near-shore waters. Inermorostrum evolved its unusual feeding style just 4 million years after the toothed whale lineage split from the branch of the family tree that includes the ancestors of today’s baleen whales such as humpbacks, which filter their food through frayed sheets of keratin, the same material in human fingernails.