At over 2.5 m (8.2 feet) in length, the newly-described stem tetrapod Gaiasia jennyae was possibly the largest creature of its kind.
Life reconstruction of Gaiasia jennyae. Image credit: Gabriel Lio.
Gaiasia jennyae lived in what is now Namibia during the Early Permian epoch, some 280 million years ago.
“Most ideas about the early evolution of tetrapods come from fossils discovered from the extensive coal-producing ancient equatorial wetlands of what is now Europe and North America,” said Universidad de Buenos Aires paleontologist Claudia Marsicano and her colleagues.
“But Gaiasia jennyae comes from much further south, living in an area of the southern supercontinent Gondwana at around 55 degrees south.”
The skull and jaw structure indicate that Gaiasia jennyae had a powerful bite capable of capturing large prey.
“Gaiasia jennyae was considerably larger than a person, and it probably hung out near the bottom of swamps and lakes,” said Dr. Jason Pardo, a postdoctoral researcher at the Field Museum.
“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.”
The nearly complete skeleton of Gaiasia jennyae after preparation. Image credit: Claudia Marsicano.
Fossils of at least four individuals of Gaiasia jennyae, including skull fragments and an incomplete vertebral column, were recovered from the Gai-As Formation in northwestern Namibia.
“When we found this enormous specimen just lying on the outcrop as a giant concretion, it was really shocking,” Dr. Marsicano said.
“I knew just from seeing it that it was something completely different. We were all very excited.
“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.”
“We had some really fantastic material, including a complete skull, that we could then use to compare with other animals from this age and get a sense of what this animal was and what makes it unique. It turns out, there’s a lot about the creature that makes it special,” Dr. Pardo added.
Gaiasia jennyae is related to extinct amphibian-like animals called colosteids (family Colosteidae) that are more characteristic of an even earlier age and are thought to have been replaced by more modern amphibians and reptiles in the Late Carboniferous epoch, around 307 million years ago.
“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,” Dr. Pardo said
“Gaiasia jennyae is big, and it is abundant, and it seems to be the primary predator in its 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.”
“The fact that we found Gaiasia jennyae 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.”
The team’s findings were published in the journal Nature.
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C.A. Marsicano et al. Giant stem tetrapod was apex predator in Gondwanan Late Palaeozoic Ice Age. Nature, published online July 3, 2024; doi: 10.1038/s41586-024-07572-0
