Echolocation may have been present in a 28-million-year old ancestor of toothed whales and dolphins.
Researchers discovered a new fossil species, dubbed Cotylocara macei, that employed high frequency vocalizations, a New York Institute of Technology news release reported.
"The most important conclusion of our study involves the evolution of echolocation and the complex anatomy that underlies this behavior," study leader and Associate Professor Jonathan Geisler, said in the news release. "This was occurring at the same time that whales were diversifying in terms of feeding behavior, body size, and relative brain size."
Toothed whales and dolphins produce these high frequency sounds through a "constricted area in the nasal passages," the news release reported. This sound-producing mechanism is complex and requires strong muscle power and air pockets.
Studies of a Cotylocara macei skull concluded the the ancient animal also used echolocation.
"Its dense bones and air sinuses would have helped this whale focus its vocalizations into a probing beam of sound, which likely helped it find food at night or in muddy water ocean waters," Geisler said.
The researchers compared the fossils with living whales and determined that the Cotylocara belonged to a "distinct" whale family that broke off from other species some 32 million years ago. An analysis of the toothed whales' family tree suggests echolocation first appeared in a common ancestor of the Cotylocara and other similar whales that swam the seas between 35 and 32 million years ago.
Over the course of the generations the size and complexity of the system's air sacs gradually increased as well as the muscles that controlled the sound.
Cotylocara also had a deep cavity in its head that led to an air sinus used for storage while diving; the cavity also may have helped amplify the high frequency sound. A radar-like dish made of bone found around the nasal openings also may have helped reflect sound.
"The anatomy of the skull is really unusual. I've not seen anything like this in any other whale, living or extinct" Geisler said.
