Paleontologists in Brazil have identified a previously unknown species of early tetrapod, a four-limbed vertebrate, distinguished by a uniquely twisted jaw and sideways-facing teeth. The discovery, detailed Wednesday in the journal Proceedings of the Royal Society B, suggests the creature, named Tanyka amnicola, was a surviving member of an ancient lineage thought to have largely disappeared by the Permian period, approximately 275 million years ago.
The findings are based on nine fossilized lower jawbones unearthed from a dry riverbed in northeastern Brazil. Each jawbone measures roughly six inches in length and exhibits a pronounced curvature. Researchers initially suspected a deformity, but the consistent presence of the twist across all specimens confirmed it as a defining characteristic of the species, according to Jason Pardo, a research associate at the Field Museum in Chicago and lead author of the study.
“The jaw has this weird twist that drove us crazy trying to figure it out,” Pardo said in a press release. “We were scratching our heads over this for years, wondering 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.”
Tanyka amnicola’s jaw structure isn’t the only unusual feature. The inner surface of the lower jaw, typically facing the tongue, is rotated upward and covered in a series of small, tooth-like structures called denticles. This arrangement would have created a grinding surface, suggesting a unique feeding mechanism. Researchers hypothesize that T. Amnicola may have consumed small invertebrates or even plant material, a dietary habit uncommon among other known stem tetrapods, which are believed to have been primarily carnivorous.
The discovery positions Tanyka as a “living fossil” in its time, akin to the modern-day platypus, which represents a surviving branch of ancient mammals. “Tanyka is from an ancient lineage that we didn’t know survived to this time, and it’s also just a really strange animal,” Pardo explained. “In the sense that Tanyka was a remaining member of the stem tetrapod lineage, even after newer, more modern tetrapods evolved, Tanyka is a little like a platypus.”
The geological context of the fossil find indicates that Tanyka amnicola inhabited lake environments during the Permian period, when Brazil was part of the supercontinent Gondwana. Study co-author Ken Angielczyk, a curator of paleomammalogy at the Field Museum, stated that the discovery offers insights into the ecological dynamics of Gondwana during this era. “Tanyka is telling us about how this community actually worked, how it was structured, and who was eating what,” Angielczyk said.
While the jawbones provide significant clues, the lack of other fossilized remains limits a comprehensive understanding of Tanyka amnicola’s anatomy and lifestyle. Researchers estimate the creature may have reached a length of approximately three feet, based on comparisons with related species.
