November 24, 2014
A whale of a find: Fossil sheds light on cetacean sonar's origin
The deadly threat posed by German submarines during World War One helped spur scientists to develop sonar, using underwater sound signals to locate objects like subs that might be taking aim with a torpedo.
In the 20th century, it was an important technological breakthrough.
But it was old technology as far as whales go. These marine mammals have been using echolocation - bouncing high-frequency sounds off underwater objects - to find prey for tens of millions of years.
US scientists announced the discovery of the most ancient whale known to have used echolocation - a creature called Cotylocara macei, a bit larger than a bottlenose dolphin, that lived about 28 million years ago.
The discovery suggests that echolocation evolved in toothed whales - the group that includes modern day varieties like sperm whales, killer whales, dolphins and porpoises - perhaps 32 million to 34 million years ago, the scientists said.
That was relatively soon after whales, around 35 million years ago, split into two major cetacean groups - toothed whales that were active hunters and toothless baleen whales that were filter feeders, straining food like krill from the ocean.
Jonathan Geisler, an anatomy professor at New York Institute of Technology who led the research published in the journal Nature, called echolocation "an amazing trait."
"It's a sonar-like system which allows them basically to navigate and find food, particularly in waters where there's little light, either at great depth or in very turbulent waters with a lot of mud, like estuaries or around marshes," he added.
Cotylocara, whose fossilized remains include a 22-inch (56 cm) skull, neck vertebrae and ribs, was about 10 to 11 feet (3 to 3.4 meters) long and probably swam in a shallow ocean environment, feeding on fish and squid, Geisler said.
The fossils were unearthed near Summerville, South Carolina, outside Charleston, said College of Charleston geology professor James Carew, another of the researchers.