Sperm whales do it. Dolphins do it. Orcas do it. And now, researchers have unveiled the fossilized skull of a 28-million-year-old marine mammal that did it too – used sound to find its next meal or swim safely through turbid waters.
The creature, Cotylocara macei, is the earliest known cetacean to show skeletal evidence for a natural form of sonar, according to a research team reporting the results in Thursday's issue of the journal Nature.
After comparing the nearly complete skull with those of other fossil cetaceans, the team placed C. macei on the evolutionary tree just above the common ancestor to all toothed cetaceans. That branch of the whale family uses echolocation to find its food, unlike their cousins who feed by straining seawater through boney baleen plates. Right and humpback whales are modern examples of these strainers.
The study "provides an important new piece of information on when echolocation originated, such that it originated almost immediately after the split between baleen whales and toothed whales," notes Frants Jensen, a researcher at the Woods Hole Oceanographic Institution in Woods Hole, Mass., who studies marine echolocation.
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