Scientists have long theorized that millions of years ago, whales had legs, dividing time between land and sea. And now, findings from a new in-depth study — published in the Journal of Vertebrate Paleontology — may help experts fill in the evolutionary gap between the enormous sea-faring mammals of today and their (possibly) amphibious ancestors. Here's what you should know:

What exactly were scientists studying?
An ultra-rare, 40-million-year-old specimen that "nearly wound up as a countertop," says Brian Switek at Wired. An Italian marble cutter found a strange animal's skull nested in finely cut slabs of rock. The man thought he had discovered a dinosaur. He was wrong. 

And it was an ancient whale skull?
Yep. Researchers traced the stone's origin to a limestone quarry in Egypt's Tarfa Valley, and pieced the fossil back together there. Though its bones "had been hacked into six pieces… because the cuts were so smooth," the skeleton was easily reconstructed, says Ed Yong at Discover. They dubbed the animal aegyptocetus tarfa, which translates to "Egyptian whale from Tarfa." 

So what was this whale like?
The ancient whale belonged to a group of mammals related to modern toothed whales and dolphins. Its skull was more than two feet long, and the creature itself likely weighed more than 1,400 pounds. It had a specially adapted skull that allowed it to hear echoes underwater, and a nose structure that suggests it was able to smell — critical for tracking prey on land. Smell is a sense that most modern whales lack. Scientists cite this as proof that these animals had "powerful legs that could support them on land as well as powering them through water." Though strangely, the legs were nowhere to be found.

Where did its legs go?
They were probably eaten. "Toothmarks on its ribcage indicate it might have been attacked from its right flank," says Jennifer Welsh at Live Science — similar to how modern sharks ambush their prey. Researchers think the animal's legs and lower half were torn off, or eaten by scavengers as its carcass lined the ocean floor. 

So whales definitely had legs?
Well, not definitely. But this evidence helps strengthen that case. Many scientists already thought modern whales evolved from hooved, deer-like creatures, and aegyptocetus could provide "valuable information about the transition from land to sea," says Yong.

Sources: Discover, Live Science, Wired