Ancient swamp creature with a toilet seat-shaped head was a top predator before the dinosaurs

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A massive, fanged creature with a head shaped like a toilet seat lurked in swamps near the edge of the world 280 million years ago, long before the first dinosaurs appeared, new research has found.

Now, scientists who made the surprising discovery of its fossils in Namibia and Brazil want to know why the archaic salamander-like predator seemed to flourish millions of years after its relatives near the equator went extinct.

They reported their study’s findings, the result of work that began in 2018, on Wednesday in the journal Nature.

“Gaiasia jennyae was considerably larger than a person, and it probably hung out near the bottom of swamps and lakes,” said co-lead study author Jason Pardo, a National Science Foundation postdoctoral fellow at the Field Museum of Natural History in Chicago, in a statement. “It’s got a big, flat, toilet seat-shaped head, which allows it to open its mouth and suck in prey. It has these huge fangs, the whole front of the mouth is just giant teeth. It’s a big predator, but potentially also a relatively slow ambush predator.”

So far, paleontologists have uncovered a well-preserved skull and spine, some partial skulls, vertebrae and jaw pieces after conducting two seasons of fieldwork. The largest skull is more than 2 feet (0.6 meters) long.

“When we found this enormous specimen just lying on the outcrop as a giant concretion, it was really shocking,” said co-lead study author Claudia Marsicano, a researcher and professor in the department of geology at the University of Buenos Aires, in a statement. “I knew just from seeing it that it was something completely different.”

Ancient polar creatures

Together, the fossil pieces tell the story of a creature that defied all expectations based on the evolutionary paths of better-known animals from the time, which mostly lived closer to the equator.

Creatures living in the far south have been harder to pin down, and less is known about the animals that lived closer to the poles.

Gaiasia lived in the middle of the Permian period, which spanned 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, according to the study.

At the time, the planet was dominated by a supercontinent called Pangea, 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.

Currently, Namibia is north of South Africa. But 300 million years ago, what is now Namibia was much farther south and located near the northernmost point of Antarctica today.

As the Permian period began, the planet was warming after the end of an ice age. While wetlands near the equator dried up and became forests, cold swamps closer to the poles remained and were framed 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 were doing their own thing, Pardo said.

“Gaiasia is a stem tetrapod — it’s a holdover from that earlier group, before they evolved and split into the groups that would become mammals and birds and 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 went extinct probably 40 million years prior.”

An unrivaled predator

Part of the reason Gaiasia is so surprising to researchers is because it was so large and dominant.

“There are some other more archaic animals still hanging on 300 million years ago, but they were rare, they were small, and they were doing their own thing,” Pardo said. “Gaiasia is big, and it is 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 about 10 feet (3 meters) in length. But it could have been twice that length, Pardo said.

Fossils of Gaiasia’s limbs, if it had any, or its tail, have yet to be found, but the researchers know where the creature fits into the tree of life, and Gaiasia’s ancestors and distant relatives had limbs. Discovering more fossils during future fieldwork could help researchers improve body size estimates, Pardo said.

What they have found so far paints a portrait of a terrifying creature you wouldn’t want to encounter, he said.

Gaiasia’s wide, flat skull was like putting two massive plates on top of each other. As the creature opened its mouth, a natural suction would occur, pulling in fish, sharks or any other nearby prey. Inside, fangs measuring 3 inches (7.6 centimeters) long were waiting to pierce prey so Gaiasia could swallow its meals whole, Pardo said.

“After examining the skull, the structure of the front of the skull caught my attention,” Marsicano said. “It was the only clearly visible part at that time, and it showed very unusually interlocking large fangs, creating a unique bite for early tetrapods.”

The research team suspects Gaiasia went extinct about 268 million years ago, but it’s unclear what caused the tetrapod to disappear.

A far south mystery

The discovery of Gaiasia is forcing scientists to ask new questions, such as how it persisted for so long in such a cold environment. Typically, such an animal would adapt to become an endotherm, a warm-blooded animal able to regulate body temperature by producing its own heat.

But Gaiasia was an ectotherm, which relied on its external environment to regulate its body temperature.

“She’s a large aquatic animal, very essentially something between a fish and an amphibian, and achieving very large body sizes,” Pardo said. “If you’re cold-blooded, that’s really hard because you have to eat a lot of food and survive for a long period of time to get big.”

It’s possible that Gaiasia lived to be 20 to 40 years old to reach such massive sizes, but researchers can’t be sure, Pardo said.

In addition to seeking more fossil examples of the species, the researchers are also curious to find other animals that lived in this far south 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 really important because there were a lot of groups of animals that appeared at this 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 flourishing ecosystem that could support these very large predators,” he added. “The more we look, we might find more answers about these major animal groups that we care about, like the ancestors of mammals and modern reptiles.”

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