Fossils of a previously unknown four-legged whale species that lived 43 million years ago in Egypt have been unearthed.

The predatory creature is the ancestor of modern-day whales and highlights the land-to-sea transition that took place about 10 million years ago.

The new whale, named Phiomicetus anubis, was about 3 meters long and had a body mass of around 590 kg, and was probably the largest predator when navigating the ancient seas.

Paleontologists have discovered fossilized remains from middle Eocene rocks in the Fayum Depression in Egypt’s Western Desert, which was once covered with seas and provides a rich array of discoveries that show the evolution of whales.

“The unique features of the skull and mandible point to a capacity for more efficient oral mechanical processing than in the typical protocetid state, thus allowing for a vigorous predatory diet,” the study says.

It may be hard to believe that the huge whales we see in the ocean today are the decedents of four-legged animals that once walked on land. However, that’s exactly what they were 50 million years ago.

In 2008, paleontologists discovered a 47-million-year-old fossil of a stocky, fox-sized animal with a long body and tail in Pakistan.

The bones stuck in the mud layer reflected characteristics of modern-day whales: there was a similar bone in the middle ear cavity and skull structure.

Hans Thewissen of Northeast Ohio Medical University and his team, who were involved in the discovery, determined that the creature, named Indohyus, swam in water like a hippopotamus to forage for food and avoid predators. Transition to a completely aquatic lifestyle!

Scientists have described the skeleton as ‘a fox-sized mammal resembling a miniature deer’.

After further analysis, the researchers discovered similarities between the skulls and ears of both whales and whales.

They determined that Indohyus’ bones had a much thicker outer layer than other mammals of the same size.

This trait is often found in mammals that are slow waterfowl, such as today’s hippos.

Another clue to how Indohyus lived was found in the thick and heavy bones of the hippo.

This suggests that the animal was a bird with heavy bones to prevent it from swimming.

Based on this evidence, Thewissen suggested that whale ancestors entered the water as a mechanism to avoid predators and did not develop specific aquatic feeding behaviors until much later.

Paleontologist Jonathan Geisler of Georgia Southern University in Statesboro has previously identified a link between saoellids and whales, but his evidence is based only on tiny tooth fragments. This new study strengthens the link, he said.

“What’s really important about these fossils is that they confirm the hypothesis that the ancestors of marine mammals lived semi-aquatic before they developed specialized teeth for eating fish,” Geisler said.

The first ancestors of whales appeared between 42 million and 48 million years ago, and resembled sea lions, Thewissen said.

Then there was the Bale whale, about 41 million years ago, including the ancestors of humpback and blue whales.

They were followed some seven million years later by toothed whales that still swim in the oceans today.

Take a look at the evolution of the whale, the largest animal in the world: