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A giant, toothy creature with a head shaped like a toilet seat was found lurking in swamps near the Earth’s coast 280 million years ago, long before the first dinosaurs appeared, according to a new study.
Now, after making a surprising discovery of fossil remains in Namibia and Brazil, scientists want to know why this archaic salamander-like predator proliferated millions of years after its relatives near the equator went extinct.
They published the results of the studies, which began in 2018, in the journal Nature on Wednesday.
“Gaiasia jennyae was significantly larger than a human and probably hung out at the bottom of marshes and lakes,” Jason Pardo, a National Science Foundation postdoctoral researcher at the Field Museum of Natural History in Chicago and co-lead author of the study, said in a statement. “It has a big, flat, toilet-seat-shaped head, which allows it to open its mouth and suck in prey. It has these huge teeth, the entire front of its mouth is made up of huge teeth. It’s a big hunter, but it’s also potentially a relatively slow ambush hunter.”
So far, after two seasons of fieldwork, paleontologists have unearthed a well-preserved skull and spine, some partial skulls, vertebrae and jaw fragments. The largest skull is more than 2 feet (0.6 meters) long.
“When we found this enormous specimen as a giant petrification on the outcrop, we were truly shocked,” study co-lead author Claudia Marsicano, a researcher and professor in the geology department of the University of Buenos Aires, said in a statement. “I just knew when I saw it that it was something completely different.”
Ancient arctic creatures
When the fossil pieces come together, they tell the story of a creature that defied all expectations based on the evolutionary paths of animals better known at the time, which lived mostly in regions close to the equator.
Creatures living in the far south are harder to detect, while less is known about animals living closer to the poles.
Gaiasia lived during the mid-Permian period, which lasted from 298.9 million to 251.9 million years ago. It thrived as a top-level predator 40 million years before dinosaurs evolved to roam the Earth, according to the study.
At that time, the planet was dominated by a supercontinent called Pangea, which included a large landmass known as Gondwana. The landmass included present-day South America, Africa, Antarctica, Australia, New Zealand, and the Indian subcontinent.
What is now Namibia is north of South Africa, but 300 million years ago, what is now Namibia was much further south, near what is now the northernmost point of Antarctica.
As the Permian period began, the planet was warming after the end of an ice age. Wetlands near the equator dried out and turned into forests, while cold marshes near the poles remained and were surrounded by glaciers and ice.
In hotter, drier regions near the equator, new animals emerged as four-legged vertebrates called stem tetrapods evolved and split into groups that formed the basis of modern animals. But that doesn’t seem to be the case at the poles, where the ancient creatures do their own thing, Pardo said.
“Gaiasia is a stem tetrapod — a holdover from that ancient group before it branched off into groups called crown tetrapods, which would evolve into mammals, birds, reptiles and amphibians,” Pardo said. “It’s really amazing how archaic Gaiasia is. It’s probably related to organisms that went extinct 40 million years ago.”
An unrivaled hunter
One reason Gaiasia was so surprising to researchers was that it was so large and dominant.
“There are older animals that were still around 300 million years ago, but they were rare, small and doing their own thing,” Pardo said. “Gaiasia is large and abundant and appears to have been the primary predator in its ecosystem.”
While the creature’s contemporaries were the size of modern eels or snakes, Gaiasia probably reached about 10 feet (3 meters) long, but Pardo said it may have been twice that long.
Fossils of Gaiasia’s limbs, if any, or its tail have not yet been found, but researchers know where the creature fits on the tree of life, and Gaiasia’s ancestors and distant relatives had limbs. Discovering more fossils during future fieldwork could help researchers refine their body size estimates, Pardo said.
“What they’ve found so far paints a portrait of a terrifying creature you wouldn’t want to encounter,” he said.
Gaiasia’s broad, flat skull was like putting two large plates on top of each other. When the creature opened its mouth, natural suction would occur, drawing in fish, sharks or other nearby prey. Inside, 3-inch (7.6-centimeter)-long teeth waited to pierce prey so Gaiasia could swallow its meals whole, Pardo said.
“After examining the skull, I was struck by the structure of the front part of the skull,” Marsicano said. “It was the only part clearly visible at the time, and it showed very unusually large interlocking teeth, creating a unique bite for early tetrapods.”
The research team suspects that Gaiasia went extinct around 268 million years ago, but it is not yet known why the tetrapod went extinct.
A mystery in the far south
Gaiasia’s discovery is forcing scientists to ask new questions, such as how it was able to survive in such a cold environment for so long. Typically, such an animal would have adapted to be an endotherm, a warm-blooded animal that can regulate its body temperature by generating its own heat.
However, Gaiasia was an ectotherm, dependent on the external environment to regulate its body temperature.
“It’s a big aquatic creature, essentially something between a fish and an amphibian, and it gets to very large body sizes,” Pardo said. “If you’re cold-blooded, it’s really tough because you have to eat a lot of food to grow and survive for a long time.”
It’s possible Gaiasia lived for 20 to 40 years to reach such a large size, but researchers can’t be sure, Pardo said.
In addition to searching for more fossil specimens of the species, the researchers are also curious to find other animals that lived in this far southern ecosystem.
“This tells us that what was happening in the far south was very different from what was happening at the equator. And that’s really important because there were a lot of animal groups that emerged during this period that we don’t really know where they came from,” Pardo said.
“The fact that we found Gaiasia so far south suggests that there was a thriving ecosystem that could support these very large predators,” he added. “The more we look, the more answers we can find about these large groups of animals that we care about, like the ancestors of mammals and modern reptiles.”
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