Prehistoric aquatic freak with sideways teeth and twisted jaw was already a ‘living fossil’ 275 million years ago

Paleontologists have revealed a strange prehistoric creature with a twisted jaw and sideways teeth. This strange underwater creature was already a “living fossil” when it existed 275 million years ago.

The newly described species, named Tanica amnicola, is an ancient member of the Tetrapoda, a large group of tetrapod 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.

Although older than dinosaurs, T. amnicola was already an evolutionary relic during the Permian period. Many of the earliest tetrapod lineages, known as pedunculated tetrapods, had already disappeared by that time. However, while the lineage to which T. amnicola belongs appears to have persisted, tetrapods as a group have diversified.

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“Tanica belongs to an ancient lineage that we have not yet survived, and it is also a truly bizarre animal,” study lead author Jason Pardo, a researcher at Chicago’s Field Museum, said in a statement. “Tanika is a bit like the platypus in the sense that it is a remaining member of the pedunculate tetrapod lineage, even after newer, more modern tetrapods evolved. At the time, it was a living fossil.”

Researchers identified the new species from nine fossilized mandibles, about 6 inches (15 centimeters) long, found in a dry riverbed in northeastern Brazil. The creature’s lower jaw bones were unique enough for the researchers to determine that the fossil was a new species, but the lack of other fossilized remains means much remains unknown about the animal.

However, given what is known about its relatives, T. amnicola may have resembled a salamander with a slightly longer snout. It could have grown up to about 3 feet (91 centimeters) long, Pardo said. The paper said the type of rock in which the fossil was found suggests the creature lived in a lake environment and probably had an “aquatic habit.”

Analysis of the lower jaw bone revealed some interesting features. Primarily, the lower jawbone is twisted, meaning the creature’s teeth point outward and to the sides, rather than upwards, as they do in virtually all quadrupeds.

“There’s a weird twist in the jaw, and we went crazy trying to figure it out,” Pardo said. “We’ve been puzzled for years that this might be some sort of deformity. But at this point, this animal has nine jaws, and they all have twists, including some that are very well preserved. So this is not a deformity, it’s just the way this animal was built.”

Additionally, the inner surface of the mandible facing the human tongue was rotated upward. According to the study, it was covered with a “remarkable” set of tiny tooth-like structures called dentata, which would have formed the grinding surface. These characteristics suggest the animal had a “relatively unique” feeding method, Pardo said.

The authors suspect that T. amnicola may have adapted to eating small invertebrates, or potentially some plant material. The researchers said this was unusual, given that there is no evidence of plant-eating or omnivorous diets in other stalked quadrupeds, which are thought to have been carnivores.

When T. amnicola was alive, Brazil was part of the Gondwana supercontinent. The discovery provides clues to the fauna of Gondwana during this period, the statement said. “Tanika is telling us how this community really functioned, how it was organized, and who ate what,” study co-author Ken Angielczyk, curator of paleontology at the Field Museum, said in a statement.