The discovery of a fossil of a previously unknown type of whale which lived about 28 million years ago suggests that these toothed mammals evolved early than thought.
The find, announced in the journal Nature, suggests that echolocation, the use of a sonar-like ability, evolved extremely early in the divergence of toothed whales — sperm whales, killer whales and dolphins — from their common ancestor with baleen whales.
The evolutionary adaptation of echolocation provided a way for species living in dark and murky water to navigate and hunt prey.
Echolocation is a distinctive feature of toothed whales (odontocetes), but little is known about how and when this complex behaviour and its underlying anatomy evolved.
Dr Jonathan Geisler of the New York Institute of Technology College of Osteopathic Medicine and colleagues describe a fossilized toothed whale from the Oligocene of South Carolina.
The animal’s skull has several features suggestive of a rudimentary form of echolocation, including cranial asymmetry and a dense upper jaw.
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