J. Vert. Paleontol. 28, 589–593 (2008)

Credit: GEORGIA SOUTHERN MUS.

The ancient whale Georgiacetus vogtlensis probably wiggled its hips and used its giant hind feet to propel itself through the water some 40 million years ago.

Examining previously unstudied bones from this species, Mark Uhen at the Alabama Museum of Natural History in Tuscaloosa discovered that the animals lacked tail flukes. G. vogtlensis could not have swum by paddling its legs, as the pelvic bones are not connected to the spine in this species, and so Uhen proposes that this whale must have undulated its hips and used its feet for propulsion.

The new find identifies G. vogtlensis as an intermediate between whales that paddled and whales that used their tails to swim. It also suggests that some early whales undulated their hips before evolving to undulate their tails.