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New research has revealed that 280 million years ago, long before the first dinosaurs appeared, a huge creature with fangs and a head shaped like a toilet seat lived in swamps at the edge of the world.
Scientists who made the surprising discovery of fossils of this species in Namibia and Brazil now want to know why this archaic salamander-like predator seemed to still be thriving millions of years after its relatives near the equator went extinct.
On Wednesday, they published the findings of their research, the result of work that began in 2018, in the journal Nature.
“Gaiasia jennyae was considerably larger than a human and probably hung out on the bottom of swamps and lakes,” study co-lead author Jason Pardo, a National Science Foundation postdoctoral fellow at the Field Museum of Natural History in Chicago, said in a statement. “It has a big, flat, toilet-seat-shaped head that it uses to open its mouth and suck in prey. It has these huge canines, the entire front of its mouth is made up of giant teeth. It’s a large predator, but it’s also probably a relatively slow ambush predator.”
So far, paleontologists have uncovered a well-preserved skull and spine, several partial skulls, vertebrae and jaw fragments after two seasons of fieldwork. The largest skull is more than 2 feet (0.6 meters) long.
“When we saw this huge specimen just lying on the rock like a giant concretion, it was really shocking,” study co-lead author Claudia Marsicano, a researcher and professor at the University of Buenos Aires’ geology department, said in a statement. “I knew just by looking at it that it was something completely different.”
Ancient Arctic Creatures
Together, the fossil pieces tell the story of a creature that defied expectations based on the evolutionary paths of more familiar animals of the time, which lived mainly closer to the equator.
It is more difficult to identify animals that live in the far south. Less is also known about animals that lived closer to the poles.
Gaiasia lived during the mid-Permian, which lasted from 298.9 million years to 251.9 million years ago. It thrived as a top predator 40 million years before dinosaurs evolved to roam the Earth, the study found.
At that time, the planet was dominated by a supercontinent called Pangaea, which included a large landmass known as Gondwana. The landmass included what is now South America, Africa, Antarctica, Australia, New Zealand, and the Indian subcontinent.
Today, Namibia lies north of South Africa. But 300 million years ago, present-day Namibia was much further south and was close to the northernmost point of Antarctica.
As the Permian began, the planet was warming after the end of an ice age. While wetlands near the equator dried out and became forests, cold swamps nearer the poles remained, surrounded by glaciers and ice.
New animals appeared in the warmer, drier regions near the equator as four-legged vertebrates called stem tetrapods evolved and split into groups that formed the basis for modern animals. But that doesn’t seem to be the case at the poles, where ancient creatures did their own thing, Pardo said.
“Gaiasia is a stem tetrapod — it’s a relic of that earlier group, before they evolved and split into the groups that would become mammals, birds, reptiles and amphibians, which are called crown tetrapods,” Pardo said. “It’s really, really surprising that Gaiasia is so archaic. It was related to organisms that probably went extinct 40 million years earlier.”
An unparalleled predator
One of the reasons Gaiasia is so surprising to researchers is because it was so large and dominant.
“There are other archaic animals that were still around 300 million years ago, but they were rare, small and doing their own thing,” Pardo said. “Gaiasia is big and abundant, and it seems to be the primary predator in its ecosystem.”
While the creature’s contemporaries would have been about the size of modern eels or snakes, Gaiasia likely reached lengths of about 10 feet (3 meters). But it could have been twice that length, Pardo said.
Fossils of Gaiasia’s limbs, if any, or its tail, have yet to be found, but researchers know where the creature fits in the tree of life, and Gaiasia’s ancestors and distant relatives had limbs. Discovering more fossils during future fieldwork could help researchers improve their estimates of body size, Pardo said.
What they’ve found so far paints a picture of a terrifying creature you’d rather not encounter, he said.
Gaiasia’s broad, flat skull resembled the stacking of two enormous plates. When the creature opened its mouth, a natural suction was created, pulling in fish, sharks or other nearby prey. Inside, 3-inch-long fangs waited to pierce prey, allowing Gaiasia to swallow its meals whole, Pardo said.
“After examining the skull, what caught my attention was the structure of the front of the skull,” Marsicano said. “It was the only clearly visible part at the time, and it showed very unusual interlocking large canines, which created a unique bite for early tetrapods.”
The research team suspects that Gaiasia became extinct around 268 million years ago, but it is unclear what caused the quadruped to disappear.
A mystery in the far south
Gaiasia’s discovery is forcing scientists to ask new questions, such as how it has survived in such a cold environment for so long. Normally, such an animal would adapt to become an endotherm, a warm-blooded animal that can regulate its body temperature by producing its own heat.
But Gaiasia was an ectotherm, relying on her external environment to regulate her body temperature.
“She’s a big aquatic animal, essentially somewhere between a fish and an amphibian, and she reaches a very large body size,” Pardo said. “When you’re cold-blooded, that’s very difficult because you have to eat a lot and survive a long time to get big.”
Pardo said it’s possible that Gaiasia lived to be 20 to 40 years old and reached such an enormous size, but researchers aren’t sure.
In addition to searching for more fossil specimens of the species, researchers are also curious about other animals that lived in this southern ecosystem.
“It tells us that what was happening in the far south was very different from what was happening at the equator. And that’s very important, because there were a lot of groups of animals that appeared at that time that we don’t really know where they came from,” Pardo said.
“The fact that we found Gaiasia in the far south tells us that there was a thriving ecosystem that could support these very large predators,” he added. “The more we look, the more answers we may find about these important groups of animals that we care about, like the ancestors of mammals and modern reptiles.”
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