Paleontologists have revealed a bizarre prehistoric creature with a twisted jaw and sideways teeth, and the aquatic oddity was already a “living fossil” when it existed 275 million years ago.
The newly described species, named Tanyka amnicolais an archaic member of the tetrapods — a large group of four-legged vertebrates that today includes reptiles, birds, mammals and amphibians, according to a study published Wednesday (March 4) in the journal Proceedings of the Royal Society B.
“Tanyka is from an ancient lineage that we didn’t know survived to this time, and it’s also just a very strange animal,” lead study author Jason Pardoa research associate at the Field Museum in Chicago, said in a statement. “In the sense that Tanyka was a residual member of the stem tetrapod lineage even after newer, more modern tetrapods evolved, Tanyka is a bit like a platypus. It was a living fossil in due time.”
Scientists identified the new species from nine fossilized lower jaw bones, each about 15 centimeters long, recovered from a dry riverbed in northeastern Brazil. Although the creature’s lower jaw bones were distinctive enough for the team to determine that the fossils represented a new species, the lack of other fossilized remains means much about the animal remains remains unknown.
So it’s not a deformation, it’s just the way the animal was made.
Jason Pardo, research assistant at the Field Museum
Given what is known about its close relatives, however T. amnicola may have resembled a salamander with a slightly longer snout. It possibly measured up to about 3 feet (around 91 centimeters) in length, Pardo said. The type of rock in which the fossils were found also indicates that the creature lived in lake environments and probably had “water habits”, according to the paper.
Analysis of the mandible revealed some intriguing features—mainly that they were twisted so that the creature’s teeth pointed outward to the sides, rather than upward as seen in virtually all other tetrapods.
“Keven has this weird twist that drove us crazy trying to figure it out,” Pardo said. “We scratched our heads over this for years and wondered if it was some kind of deformation. But at this point we’ve got nine jaws from this animal, and they all have this twist, including the really, really well-preserved ones. So it’s not a deformation, it’s just the way the animal was made.”
Furthermore, the inner surface of the mandible, which faces the tongue in humans, was rotated upwards; it was covered in a “remarkable” set of tiny, tooth-like structures called denticles that would have formed an abrasive surface, according to the study. These features suggest the animal had a “relatively unique way” of foraging, Pardo said.
The authors suspect so T. amnicola was adapted to munching on small invertebrates or, potentially, some plant material. This would be unusual, given the lack of evidence for herbivorous or omnivorous diets in other tribal theropods, which are thought to have been carnivores, the team said.
When T. amnicola lived, Brazil was a part of supercontinent Gondwana. According to the statement, the find provides a window into Gondwana’s animals during this period. “Tanyka tells us about how this community actually worked, how it was structured and who ate what,” co-author of the study Ken Angielczyka curator of paleomammology at the Field Museum, said in the statement.
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
