Divers looking for fossil megalodon teeth found a strange skull in the Wando River near Charleston, South Carolina. At the College of Charleston’s Mace Brown Museum of Natural History, paleontologist Robert Boessenecker began studying it, and came to the conclusion that it's a new type of prehistoric cetacean, one that had no teeth! That's pretty weird, as cetaceans (whales, dolphins, and porpoises) descended from land mammals that returned to the sea. This one lost its teeth along the way.
As Boessenecker and his colleagues measured the partial skull, they realized it is related to modern odontocetes, also known as toothed whales—a name that’s obviously a bit misleading. “It’s definitely a weird, weird toothed whale.” says John Gatesy, who studies cetaceans at the American Museum of Natural History and was not involved in the study. The team studying the South Carolina skull named it Inermorostrum xenops.
There actually are modern odontocetes that don’t really use their teeth either. Male beaked whales, for example, usually have one pair of teeth that is only used to fight for females, whose teeth stay completely hidden in their gums. Beaked whales, along with pilot whales and sperm whales, also catch squid by sucking them into their mouths. But all of these whales evolved recently. Inermorostrum xenops seems to have evolved its toothless suction-feeding independently and much, much earlier than modern suction-feeding whales. “It’s a highly specialized species but it’s essentially a dead end,” says Boessenecker. Evolution, far from being some linear progression, often works this way, hitting dead ends and retrying failed experiments from millions of years earlier.
In other words, this 30-million-year-old creature was an evolutionary experiment that failed. Read about Inermorostrum xenops at the Atlantic.