Whale fossil holds clue to origin of echolocation
While humans have been using sonar for almost a hundred years, some marine animals have been using sound to navigate their surroundings for millions of years. Scientists may have finally unlocked the evolutionary origins of this useful ability.
A team of researchers have announced the discovery of an ancient whale known as Cotylocara macei. This species of whale is currently the earliest known example of an animal that used echolocation to navigate through their watery domains.
The ancient whale was a bit on the small side being only slightly larger than modern bottlenosed dolphins. However, the discovery of the species indicates that toothed whales were the first marine animals to develop echolocation. Cotylocara, which swam in ancient oceans around 28 million years ago, is distantly related to modern toothed whales such as dolphins, killer whales and sperm whales. Scientists also estimate that the first marine animals that used echolocation for navigation may have existed between 32 million to 34 million years ago.
"The most important conclusion of our study involves the evolution of echolocation and the complex anatomy that underlies this behavior," said Jonathan Geisler, an associate professor from the New York Institute of Technology (NYIT). "This was occurring at the same time that whales were diversifying in terms of feeding behavior, body size, and relative brain size."
In order to use echolocation, certain cetaceans create a high pitched sound using a small, constricted passage just below their blowholes. Unlike the vocalization organs found in other animals, a whale's echolocation system is more complex, using powerful muscles and air pockets to produce powerful sound waves that can propagate through relatively large distances underwater.
"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 added.
The unique physiology of whales and dolphins allow them to use sound to find their way through oceans, hunt foot and locate other members of their species.
"The anatomy of the skull is really unusual. I've not seen anything like this in any other whale, living or extinct" said Geisler.
The fossilized Cotylocara remains were found in Summerville, South Carolina. The scientists were able to recovered various pieces of ribs, neck vertebrae and even a 22-inch skull. The skull was particularly valuable since it provided physiological clues that can be used to study the animal's echolocation abilities.
The team published their findings in the online journal Nature.