Snout of a Nile crocodile

Today, the Great Rift Valley stretches from the lower end of the Middle East all the way to South Africa. This dry strip of land is dotted with the grasslands that make up the African savannah. But it wasn’t always like that.

About 15 million years ago, this part of the world, which would later become the cradle of humanity, looked completely different. Much of the area was made up of dense rainforests and wet forests, which made it easy for predators to hide. One of the most dangerous was the giant dwarf crocodile, a ferocious predator that probably had a taste for the primates that would one day evolve into hominids.

These ancient human relatives still walked on all fours and were probably no taller than 3 or 4 feet, according to Christopher Brochu, a paleontologist at the University of Iowa. Their life in the Rift Valley must have been a risky venture, thanks to this now-extinct species of crocodile.

Brochu’s findings, published in the journal The anatomical record, show that the creature could grow to about three times the size of today’s African dwarf crocodile, a small but aggressive species found in central West Africa. And like modern crocodiles, the giant pygmy would go for anything it could swallow.

Two newly discovered dwarf crocodile species, called Kinyang makosiensis and Kinyang tchernovi, lived in present-day Kenya during the middle Miocene period. Both had wide muzzles that made them look like they were smiling, but in reality “could bite your head off,” as Broschu recently explained to News from IowaNow.

Discovery of a new species

Broshu discovered this new species of crocodile while examining a collection of fossils from the Rift Valley in Nairobi, Kenya. “Just by looking at the specimen, I could tell it was a large crocodile, but it was related to the modern pygmy crocodile, not the Nile crocodile,” he says.

The more he examined these and other similar specimens, Brochu realized that this species was completely undiscovered. The palette, snout tip, and braincase resembled the modern dwarf crocodile.

“The bigger picture is that if you look at the East African rift valley system, between 19 and 15 million years ago, that’s the type of crocodile you’re going to find,” Brochu says. This, he says, has to do with the topography of time. Unlike Nile crocodiles, which spend most of their time in the water, these crocodiles lived on land. The modern dwarf crocodile, for example, is found only in the forests of West Africa.

Dwarf crocodiles live exclusively in forested areas because they feed on the forest floor and their nesting behavior requires more vegetation. Some crocodiles dig holes in the mud to nest, while others collect vegetation to form a mound that will eventually hold their eggs. “Dwarf crocodiles (ancient and modern) are strictly mound nesters, which means they need vegetation to build their nests, and they also prefer to live on the forest floor,” Broschu says.

Why did they disappear?

We don’t know for sure why this species of ferocious hunter went extinct. But we do know that the modern dwarf crocodile survives today in what is left of the West African rainforest, much like its extinct ancestor. So the extinction was probably related to changes in topography.

Volcanic activity, Brochu says, may have caused lakes and rivers to become too alkaline. “But what we think most likely happened was a drying trend in East Africa that made it difficult for them to survive,” he says.

Modern humans, who would later evolve from the Great Rift Valley, may have dodged a bullet with the extinction of the dwarf giant. But that doesn’t mean deadly encounters between crocodiles and humans are a thing of the past. Nile crocodiles today can grow up to 20 feet in length and weigh approximately 2,000 pounds. And these mega beasts attacked 214 people just last year.

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