Predator with toilet seat-shaped head ruled Antarctic swamps in the Ice Age

Forty million years before the first dinosaurs, a formidable predator prowled the swampy waters with a skull over two feet long. Known as Gaiasia jennyae , this ancient creature had a distinctive toilet seat-shaped head and would lie in wait with its jaws agape, ready to ensnare any prey that ventured too close.

Describing this newly discovered fossil, co-lead study author Jason Pardo says, “ Gaiasia jennyae 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.” Pardo talked about Gaiasia jennyae in detail with Interesting Engineering .

The name Gaiasia jennyae honors both the Gai-as Formation in Namibia, where it was discovered, and Jenny Clack, a paleontologist renowned for her work on the evolution of early tetrapods—the four-limbed vertebrates that evolved from lobe-finned fishes and eventually led to amphibians, reptiles, birds, and mammals.

The ice age messenger

Claudia Marsicano from the University of Buenos Aires, the other co-lead author of the study, and her colleagues discovered the fossil. “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.”

Three hundred million years ago, Namibia was situated close to the northernmost point of present-day Antarctica, during the tail end of an ice age . While equatorial swamps were drying and becoming forested, swamps near the poles persisted. In these colder regions, older forms of life like Gaiasia thrived.

When asked about what this fossil tells us about the ecosystems that existed 300 million years ago, Pardo tells IE , “Large animals need a lot of food. Gaiasia shows that there must have been well-established ecosystems even in these colder areas in the far south.”

The top predator in its ecosystem

Pardo describes Gaiasia as a “stem tetrapod,” telling IE, “ Gaiasia has some particular bones and other features that are lost soon after tetrapods evolved. So, the lineage leading to Gaiasia must have gone its own way long before the lineages leading to modern mammals, reptiles, and amphibians evolved .”

The tetrapod, although an ancient holdover, was a dominant and abundant predator in its habitat. Pardo explains , “Europe and North America were tropical at that time and, in those ecosystems, most archaic tetrapods became rare or extinct starting 307 million years ago as the climate became warmer and drier and as relatives of modern amphibians, reptiles, and mammals became more abundant.”

“Where archaic tetrapods survive, they’re normally small, rare, and highly specialized. Gaiasia is different: it’s common, and it’s the top predator in its environment. That’s unexpected.”

Expanding upon the predatory advantage that the animal’s toilet seat-shaped head provided, Pardo says, “In modern animals, a round flat head allows predators to create a vacuum when they open their mouth, pulling food into it. The huge teeth would have been for grabbing and killing prey: fish, freshwater sharks, other tetrapods, and perhaps even smaller Gaiasia .”

This discovery offers significant insights into the changing world during the Permian period. “When Gaiasia was alive, the southern hemisphere was just coming out of a major ice age . The fact that Gaiasia is so large shows that when the ice melted, these regions immediately became home to diverse ecosystems rather than remaining barren,” Pardo concludes.

The study was published in Nature .