A bizarre prehistoric creature with a twisted jaw and sideways-facing teeth was already a “living fossil” when it swam the ancient waters 275 million years ago.
Paleontologists have introduced Tanyka amnicola, an unusual early tetrapod—a broad group that today includes reptiles, birds, mammals, and amphibians. The find was described in a study published March 4 in the Proceedings of the Royal Society B.
Lead author Jason Pardo, a research associate at the Field Museum in Chicago, notes that Tanyka hails from an ancient lineage that didn’t disappear as later, more modern tetrapods emerged. In some ways, the animal resembles a platypus—a living fossil in its own time.
The new species is known from nine fossilized lower jawbones, each about 6 inches (15 centimeters) long, uncovered in a dry riverbed in northeastern Brazil. The fossils clearly indicate a new species, but the lack of other remains leaves many questions about the animal’s full appearance and lifestyle.
It’s not a deformity. The jaw shape is an inherent feature of the creature.
Based on what researchers know about close relatives, T. amnicola might have looked like a salamander with a slightly extended snout and could have reached roughly 3 feet (about 91 centimeters) in length. The geological context suggests the animal lived in lake environments and likely led an aquatic lifestyle.
A striking finding is the lower jawbone’s twist: the teeth pointed outward to the sides rather than upward as is typical for most four-legged vertebrates. The jaw’s interior surface, which would face the tongue in humans, was rotated upward and lined with small denticles that would have formed a grinding surface. These traits point to a distinctive feeding method.
The researchers propose that T. amnicola fed on small invertebrates, or perhaps even some plant material. This would be unusual among stem tetrapods, which are generally thought to have been carnivorous.
At the time, Brazil was part of the ancient supercontinent Gondwana. The discovery provides a snapshot of Gondwana’s animal life during this period, offering clues about how these communities were structured and who ate whom.
Co-author Ken Angielczyk of the Field Museum emphasizes that Tanyka helps illuminate the ecology of its ecosystem, revealing the interactions within this ancient community.
Article details: Pardo, J.; Marsicano, C.; Smith, R.; Cisneros, J.; Angielczyk, K.; Fröbisch, J.; Kammerer, C.; Richter, M. (2026). An aberrant stem tetrapod from the early Permian of Brazil. Proceedings of the Royal Society B. https://doi.org/10.1098/rspb.2025.2106
Note: The article includes background on Aristos, a freelance science reporter contributing to discussions on archaeology and paleontology, among other topics.
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