Representing a vital stage in the early evolution of whale locomotion, paleontologist Dr. Philip Gingerich and his research team at the University of Michigan have identified and cataloged an entirely new species of Eocene Period whale in the Egyptian desert.

The fossilized specimens of what has now been officially named Aegicetus gehennae were first unearthed in the Western Desert of Egypt in 2007, and have been found to date back approximately 35 million years. According to Gingerich, this one-ton prehistoric creature seems to have been able to propel itself through water using undulations of its mid-body and tail, similar to the way modern crocodiles swim.

Credit: Philip Gingerich - University of Michigan paleontologist Philip Gingerich recording information at the Aegicetus site.

According to a study published last week in the online scientific journal PLOS One, this new genus and species of extinct protocetid whale came from the Gehannam Formation of Wadi Al Hitan (Valley of Whales), a UNESCO World Heritage Site. It is remarkable in that it marks a clear departure from these aquatic animals' primitive foot-paddling swimming abilities and transitioning into tail-powered locomotion.

Credit: Gingerich et al in PLOS ONE - Cervical and thoracic vertebrae of Aegicetus.

According to the research paper, protocetidae are extinct, semi-aquatic whales known from middle Eocene strata in Africa, Asia, North America, and South America. Most were foot-powered beasts with hind limbs secured to the vertebral column via a solid sacrum. Today's whales all use their tails to travel through Earth's oceans, so this revealing find shines a light on how and when this shift occurred.

Credit: Philip Gingerich - Paleontologist Mohammed Sameh Antar, third from left, supervising the 2007 Aegicetus excavation.

“It is the youngest-known protocetid, dating to around 35 million years ago, and is known from one exceptionally complete skeleton and a partial second specimen, making it among the best-preserved ancient whales,” said Dr. Gingerich and his colleagues in a statement. “Compared with earlier whales, it has a more elongated body and tail, smaller back legs, and lacks a firm connection between the hind legs and the spinal column.

Credit: Gingerich et all in PLOS ONE - Lumbar, sacral and caudal vertebrae of Aegicetus.

“These adaptations indicate an animal that was more fully aquatic and less of a foot-powered swimmer than its ancestors," they add. "The body shape of Aegicetus gehennae is similar to that of other ancient whales of its time, such as the famous Basilosaurus."