Right around the time that Homo sapiens first began expanding across East Africa in hunter-gatherer groups, a mysterious type of giant lion roamed the savanna and tropical forests.

An analysis of a recently discovered fossilized skull suggests that around 200,000 years ago, members of the current lion species, Panthera leo, were either a lot bigger or a previously unknown sister species of massive lions was thriving in their place.

According to the international team of paleontologists who studied and dated the find, unearthed in the Natodomeri region of northern Kenya, lions once had one of the widest geographic distributions of any mammalian species – inhabiting areas throughout Africa, up into Eurasia and down the entire eastern half of North America.

“The skull is remarkable for its very great size, equivalent to the largest cave lions of Pleistocene Eurasia and much larger than any previously known lion from Africa, living or fossil,” they wrote in the Journal of Paleontology.

Measuring in at more than 38 centimeters (15 inches) in length, the skull is about 22 percent longer than those of the largest recorded modern-day lions, and most closely matches the size range of the extinct North American cave lion.

Although the authors do not make estimates of the animal’s overall size, if the Natodomeri lion’s body plan was also similar to the American cave lion, we’re looking at a ballpark of 1.6 to 2.5 meters (5.2 to 8.2 feet) from the tip of the nose to the base of the tail and a total weight of 175 to 235 kilograms (386 to 518 pounds).

Lions first evolved in Africa 244,000 years ago and began to migrate outwards, splitting into regional subspecies soon after. But despite millennia of continual inhabitation, the fossil record on the continent is actually quite poor compared with Europe and North America.

As such, it’s hard to say whether the fossil represents the ancient form of Panthera leo – much bigger at the time – or a truly distinct species.

Speculating about which conclusion is more likely, the authors point to a well-documented biological pattern wherein animals get larger the closer they live to the poles and during periods of colder climate. And yet, Notodomeri is extremely close to the equator, and weather patterns in the region 200,000 years ago were cooler than today but still far from glacial. Plus, modern-day lions are nearly indistinguishable from 2 million-year-old fossils of lions found elsewhere in Africa.

Thus, it seems a bit far-fetched that Panthera leo shot up in size then shrank again within such a short time.   

Research has shown that the ancient Notodomeri river delta was a lush ecosystem capable of hosting large groups of the enormous, now-extinct Pleistocene creatures known as megafauna.

Given the current evidence, the researchers believe that the fossil comes from an “extinct, distinct population or subspecies” that thrived off the area’s giant buffalo, towering mega-elephants, and perhaps, terrified early man.