This giant tetrapod sucked in prey with its ‘toilet seat-shaped’ head

The salamander-like Gaiasia jennyae stalked the swamps 300 million years ago.
a nearly complete skeleton of a salamander-like creature that lived 300 million years ago. it's head is round and shaped like a toilet seat
The nearly complete and articulated skeleton of Gaiasia jennyae after preparation. Claudia Marsicano

Millions of years before Tyrannosaurus rex stalked the Earth, a salamander-like predator terrorized ancient swamps. Gaiasia jennyae could likely grow to over eight feet long and boasted a set of interlocking jaws to gobble up anything that tried to swim past it. This newly discovered tetrapod with a funky shaped head is described in a study published July 3 in the journal Nature

Gaiasia jennyae was considerably larger than a person, and it probably hung out near the bottom of swamps and lakes. 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,” Jason Pardo, a study co-author and postdoctoral fellow at the Field Museum in Chicago, said in a statement. “It’s a big predator, but potentially also a relatively slow ambush predator.”

An illustration of Gaiasia jennyae in its swampy, Permian home. CREDIT: Gabriel Lio.

It lived during the early Permian period (about 280 million years ago). It was found in the Gai-as Formation in present day Namibia. Gaiasia was an early tetrapod, or a four-limbed land vertebrate. With a skull of almost two feet long itself, Gaiasia is potentially one of the largest creatures of its kind.

“When we found this enormous specimen just lying on the outcrop as a giant concretion, it was really shocking. I knew just from seeing it that it was something completely different. We were all very excited,” study co-author and University of Buenos Aires paleontologist Claudia Marsicano said in a statement. “After examining the skull, the structure of the front of the skull caught my attention. 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.”

[Related: New proto-amphibian species named after Kermit the Frog.]

During the dig, the team found several specimens, including a well-preserved, articulated skull and spine. The complete skull allowed the team to get a strong sense of what it looked like and made it stand out. However, its large noggin is not the only thing that makes Gaiasia an interesting find. 

Most of our knowledge about the early evolution of tetrapods come from fossil specimens discovered in what is now Europe and North America, but Gaiasia was discovered much further south. Namibia is just north of South Africa, but the country was further south about 300 million years ago. It was near the 60th parallel, roughly even with Antarctica’s northernmost point. This giant swamp-dweller lived in an area of the great southern supercontinent Gondwana, when the Earth was getting close to the end of an ice age. Swampy land near the equator was drying up and becoming more covered with trees. However, the areas closer to the poles still had swamps that were potentially alongside patches of ice and glaciers. 

In the warmer, drier parts of the world animals were evolving to new forms. Some early four-legged vertebrates–stem tetrapods–began to diverge and split into separate lineages that would eventually become mammals, reptiles, and amphibians. In places like present-day Namibia, more ancient forms of these animals remained. 

[Related: Mudskippers blink—and that’s a huge evolutionary clue.]

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,” said Pardo. “It’s really, really surprising that Gaiasia is so archaic. It was related to organisms that went extinct probably 40 million years prior.”

The authors also believe that Gaiasia was also doing fairly well for itself as a top predator. More archaic animals were still living 300 million years ago, but they were smaller and in fewer numbers. The fossil record shows that Gaiasia was abundant, large, and likely the ecosystem’s dominant animal. Even though Gaiasia jennyae is one species, it still offers clues about how the Earth was changing during the Permian period

“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,” said Pardo. “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. 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.”