Modern whales' ancestors were deer-like animals who decided they’d had enough of life on land and wandered into the sea. The evolution, which saw them transform over 10 million years into the legless giants we know today, saw many revisions of the whale body plan, and a new one has been described in a new paper.
Named Phiomicetus anubis, after the jackal-headed Egyptian god of the dead, it was about three meters (9.8 feet) long and weighed in at 600 kilograms (1,323 pounds). It was likely at the higher end of the food chain.
The paper, published in the journal Proceedings of the Royal Society B, builds an image of P. Anubis from a partial skeleton retrieved from Egypt's Western Desert. It’s taken its time getting discovered, having lived around 43 million years ago – but now it’s on the radar of researchers, it’s making quite the impression.
“Phiomicetus anubis is based on a partial skeleton and reveals that it is the most basal (primitive) protocetid whale known from Africa,” study author Abdullah Gohar told IFLScience. “Moreover, Phiomicetus further shows that the protocetid whales had already diversified in their anatomy and feeding behavior, more than was previously thought, showing a capacity for more efficient oral processing of prey items than the normal protocetid condition, thereby allowing for a strong 'raptorial' feeding style."
"Phiomicetus was likely a top predator in the community in which it lived, perhaps like a killer whale of today,” Gohar said.
The theory goes that whales became so watery as their ungulate ancestors began foraging along the water’s edge. Here, they were well placed to hide in the shallows when trouble came knocking, and as they spent more and more time in the water their bodies began to change.
Their pursuit of a new ecological niche led to a number of adaptations that would eventually see their legs disappear and their arms transformed into the flippers the cetaceans are so famous for today. For P anubis, some adaptations for aquatic life had already begun to creep in – though they were far more nuanced.
“Compared with earlier whales, it has a more elongated temporal fossa, larger third lower incisor, and longer articulation area between the mandibles” explained Gohar. “These adaptations indicate an animal that was a more successful predator than its relatives.”
Far from its grazing ancestors, P. anubis was a competent predator capable of taking down large prey, comparable to a killer whale. Combined with the toothy remains that inspired its comparison to a jackal-headed god, the prospect of P. anubis and its four limbs swimming around in the oceans certainly doesn't paint a picture of a sea in which you’d want to be.
The exciting find opens up new doors for Gohar and colleagues, raising the possibility that there may be more early semiaquatic whales waiting to be discovered in Egypt’s paleontological past, prompting a reevaluation of early whale evolution.
“Phiomicetus has not only added to our knowledge about the early whale transitional forms but has also raised new questions about the ancient ecosystems in which it lived, and has directed our new research vision toward finding answers to big questions such as the origin and coexistence of ancient whales in Egypt,” concluded Gohar.