A great deal of mystery surrounds how the anatomy of the first whales changed to propel them through the water. A key piece of that puzzle would be the discovery of when exactly the wide flukes on their powerful tails arose.
"The origin of flukes is one of the last steps in the transition from land to sea," explained vertebrate paleontologist Mark Uhen of the Alabama Museum of Natural History in Tuscaloosa.
To shed light on this mystery, Uhen analyzed new fossils that amateur bone hunters discovered exposed along riverbanks in Alabama and Mississippi. These bones once belonged to the ancient whale Georgiacetus, which swam along the Gulf Coast of North America roughly 40 million years ago, back when Florida was mostly submerged underwater. This creature reached some 12 feet in length and likely used its sharp teeth to dine on squid and fish.
The first whales known to possess flukes are close relatives of Georgiacetus that date back to 38 million years ago. But while only about 2 million years separate Georgiacetus from these other whales, Uhen now finds that Georgiacetus apparently did not possess flukes. The new 2-inch-long tail vertebra he analyzed — one of some 20 tail vertebrae the ancient whale had — is not flattened as the vertebrae near whales flukes are.