Fossil remains of strange creature with twisted jaw and sideways teeth discovered

A group of paleontologists working in a dried riverbed in Brazil have uncovered jaw bones that rewrite a corner of early tetrapod diversity. The fossils — nine pieces in total — belong to an animal with a strikingly twisted lower jaw and teeth that point outward instead of straight up and down, an arrangement unlike anything seen in its relatives.

Researchers say the remains belong to a previously unknown species, and the odd dental layout points to a feeding style built for grinding plants. The find sheds new light on life in Gondwana during the early Permian and hints at how some ancient lineages persisted alongside more modern tetrapods.

New species named Tanyka amnicola: what the name means and where it was published

The team described the species in Proceedings of the Royal Society B under the scientific name Tanyka amnicola. The genus name, drawn from the local Guaraní language, refers to the jaw, while the species name means “river-dweller,” a nod to the fossils’ riverbed origin.

The discovery was made by an international research team digging through the Pedra de Fogo Formation in northeastern Brazil, a rare fossil window into life in Gondwana hundreds of millions of years ago.

Unusual jaw structure and sideways teeth: key anatomical features

The most remarkable characteristic of the bones is a consistent twist in the lower jaw. Multiple specimens show the same deformation, indicating that the twist is an inherited anatomical feature rather than post-burial damage.

• Twisted lower jaws: all nine specimens display a pronounced torsion along the jaw margin.
• Sideways-directed teeth: several larger teeth are angled outward and to the sides, not vertically.
• Dense denticles: rows of much smaller teeth line the inner surfaces of the jaws, forming a rough, grinding surface.

How these parts probably worked together

Although bones from the upper jaw have not yet been found, researchers infer that the denticles on the lower jaw likely contacted similar structures above, producing a rasping or grinding motion. This arrangement would have been efficient for breaking down plant material — a sharp contrast with the primarily carnivorous diets of many related early tetrapods.

Where Tanyka fits in the tetrapod family tree

Scientists classify this animal among stem tetrapods — early members of the four-limbed vertebrate lineage that existed before the major branches that led to modern amphibians, reptiles, birds and mammals had fully diverged. Some stem tetrapods eventually gave rise to the land egg–laying lineages, while others remained tied to watery environments.

Tanyka appears to be a holdover lineage, a kind of evolutionary throwback that persisted alongside newer tetrapods. Researchers compare its persistence to that of a living fossil: retained ancestral traits that remained successful in specific habitats long after related forms evolved more modern anatomies.

Size, likely habitat, and diet suggested by the fossils

From the available material, paleontologists estimate the animal’s total length at up to about three feet. The geological context of the finds — sediments deposited in lake and river environments — supports the idea that this species spent much of its life in freshwater settings.

• Estimated length: up to ~3 feet (about 1 meter)
• Habitat: freshwater lakes and river systems
• Diet: likely herbivorous or omnivorous, using denticles and outward-pointing teeth to process plants

Researchers note that the grinding surface formed by denticles would have allowed this animal to handle tougher vegetation than many of its contemporaries.

Geological and paleogeographic context: Pedra de Fogo Formation and Gondwana

The Pedra de Fogo Formation records an early Permian landscape in what was then part of Gondwana — the southern supercontinent that included present-day South America, Africa, Australia and Antarctica. Fossils from this formation provide rare insight into southern hemisphere ecosystems of the period.

Tanyka adds a new piece to that puzzle, revealing a niche occupied by herbivorous stem tetrapods in aquatic or semi-aquatic settings and helping reconstruct food webs from a time when terrestrial faunas were undergoing major evolutionary shifts.

Who worked on the study and what comes next for the research

The study was led by paleontologists collaborating across institutions, including specialists at a major natural history museum in the United States and researchers in Brazil. Because bones beyond the jaws are fragmentary or absent, the team stresses that many aspects of Tanyka’s anatomy and lifestyle remain uncertain.

• Specimens analyzed: nine jaw bones recovered from the same locality
• Primary limitation: lack of associated upper jaw and postcranial material
• Next steps: targeted fieldwork to find more complete skeletons and detailed comparative analysis with related stem tetrapods

Scientists say a more complete skeleton would be needed to pin down body shape, locomotion, and precise relationships within the stem tetrapod group. Until then, the twisted jaw and grinding denticles remain the most distinctive clues to how this animal lived and fed.

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Michael Thompson

Michael Thompson is an experienced journalist covering U.S. and global news. With ten years on the front lines, he breaks down political and economic stories that matter. His precise writing and keen attention to detail help you grasp the real‑world impact of every event.