C.Marsicano
Gaiasia jennyaea newly discovered freshwater predator with a body length of 4.5 meters, lurked in the swamps and lakes about 280 million years ago. Its broad, flattened head had powerful jaws full of enormous fangs, ready to catch any prey that had the misfortune to swim by.
The problem is that, as far as we know, it should not have been that big, should have been extinct tens of millions of years before it apparently lived, and should not have been found in northern Namibia.Gaiasia “This is the first really good look we have at a completely different ecosystem that we didn’t expect to find,” says Jason Pardo, a postdoctoral researcher at the Field Museum of Natural History in Chicago. Pardo is a co-author of a study on the Gaiasia jennyae discovery recently published in Nature.
Common ancestors
“Tetrapods were the animals that crawled out of the water about 380 million years ago, maybe a little bit earlier,” Pardo explains. These ancient creatures, also known as stem tetrapods, were the common ancestors of modern reptiles, amphibians, mammals and birds. “Those animals lived until what we call the end of the Carboniferous period, about 370-300 million years ago. Very few survived and they survived longer, but they largely died out around 370 million years ago,” he adds.
This is why the discovery of Gaiasia jennyae in the 280 million year old rocks of Namibia was so surprising. Not only was it not extinct when the rocks it was found in were deposited, but it dominated its ecosystem as a top predator. By today’s standards, it was like stumbling upon a remote island where animals that should have been dead for 70 million years lived, like a living, breathing T-rex.
The skull of gaiasia “We found it is about 26 inches long. We also have a front of her torso. We know she was at least 8 feet long, probably 12, 15 feet long — a big head and a long, salamander-like body,” Pardo said. He told Ars that gaiasia was a suction feeder: it opened its jaws underwater, creating a vacuum that sucked in its prey. But the large, interlocking canines reveal that a powerful bite was also one of its weapons, probably used to hunt larger animals. “We suspect gaiasia fed on bony fish, freshwater sharks and perhaps even other, smaller gaiasia“, says Pardo, suggesting it was a fairly slow predator that could only hunt by ambush.
But considering where the animal was found, the fact that it had enough prey to raid is perhaps even more shocking than the animal itself.
Location, location, location
“Continents were organized differently 270–280 million years ago,” Pardo says. At that time, a megacontinent called Pangaea had already broken up into two supercontinents. The northern supercontinent called Laurasia included parts of modern North America, Russia, and China. The southern supercontinent, home to gaiasiawas called Gondwana, which consisted of present-day India, Africa, South America, Australia and Antarctica. And Gondwana was pretty cold then.
“Some researchers suggest that the entire continent was covered in glacial ice, much like we saw in North America and Europe during the ice ages 10,000 years ago,” Pardo says. “Others argue that it was more patchy — there were places where there was no ice,” he adds. Yet 280 million years ago, northern Namibia was at about 60 degrees south latitude — about where the northernmost parts of Antarctica are today.
“Historically, we thought that quadrupeds [of that time] lived just like modern crocodiles. They were cold-blooded, and if you are cold-blooded, the only way to grow big and stay active is to be in a very warm environment. We believed that such animals could not live in colder environments. Gaiasia shows that it absolutely is not the case,” Pardo claims. And this turned much of what we knew about life on Earth on its head in gaiasia‘s time.