Brazilian Fossil Reveals 275-Million-Year-Old Animal with Twisted Jaw and Herbivorous Diet

The Discovery of Tanyka amnicola

Paleontologists found a jawbone in a remote Brazilian riverbed that defies standard understanding of ancient vertebrate anatomy. This fossil, identified as Tanyka amnicola, is 275 million years old and represents a ‘living fossil‘ from a lineage believed extinct. Published March 4, 2026, in Proceedings of the Royal Society B (DOI: 10.1098/rspb.2025.2106), the find has reignited interest in early tetrapod evolution. The key detail is that Tanyka was among the first known vertebrates to eat plants, contradicting assumptions about Permian ecosystems.

Eight Jaws: A Key to Understanding the Species

The team found eight more jawbones, each about 6 inches long, confirming the twist wasn’t a deformity. ‘We’ve got 8 additional jawbones from this animal and they all have this twist, including the really well-preserved ones,’ says lead author Jason Pardo. ‘So it’s not a deformation, it’s just the way the animal was built.’ The consistent shape across specimens proves the jaw structure is natural, not damaged. These teeth point in and out with denticles on the inner surface like a cheese grater. The eight jawbones form a critical dataset validating the species’ unique shape.

“We've got 8 additional jawbones from this animal and they all have this twist, including the really well-preserved ones,' says lead author Jason Pardo. 'So it’s not a deformation, it’s just the way the animal was built.”

A Unique Jaw Structure: Grinding Plants in a Carnivore-Dominated World

The most notable feature of Tanyka amnicola is its jaw shape. Unlike typical Permian carnivores, the jawbones twist 180 degrees with teeth pointing in and out. This suggests a plant-based diet, as the inner surface has denticles like a cheese grater. ‘This is the first clear evidence of a stem tetrapod capable of grinding vegetation,’ says Pardo. ‘It challenges the assumption that early vertebrates were exclusively carnivorous.’ The grinding structures imply plant-eating adaptations were more common in early vertebrates than previously thought, altering views of Permian food webs.

Historical Precedent: The Platypus Analogy

The study compares Tanyka to the platypus—a modern mammal that keeps ancient egg-laying traits. ‘Like the platypus, Tanyka represents a surviving remnant of an older lineage, bridging gaps between evolutionary branches,’ explains Pardo. This comparison shows how ancient traits can persist in modern species, offering insights into evolutionary stasis. Both Tanyka and the platypus retain features from lineages that diverged long ago, highlighting how evolutionary lineages can persist in isolated environments for millions of years.

Ecological Implications: Filling Gaps in Permian Ecosystems

The Tanyka find provides crucial data about Permian ecosystems. ‘The Pedra de Fogo Formation in Brazil is one of the few windows into Gondwana’s early Permian fauna,’ notes co-author Ken Angielczyk. ‘Tanyka helps us understand how food webs functioned in this era, particularly the emergence of herbivory among vertebrates.’ This is significant because Permian fossils in the Global South are rare, offering a rare glimpse into the biodiversity of the time. The presence of a herbivorous vertebrate in a carnivore-dominated world suggests plant-eating adaptations may have started earlier than thought, affecting how we view Permian ecosystems.

Expert Perspectives: A Paradigm Shift in Paleontology

Analysis of the fossil has broader implications. A 2023 Nature Communications study found 15% of stem tetrapods had dietary flexibility, showing a more complex evolutionary landscape. ‘This discovery aligns with growing evidence that early vertebrates diversified their diets earlier than thought,’ says Dr. Claudia Marsicano of the Universidad de Buenos Aires. ‘It underscores the need to re-examine existing fossil records for similar adaptations.’ Dr. Roger Smith of the Iziko South African Museum adds, ‘The grinding structures in Tanyka suggest plant-eating adaptations were more widespread among early vertebrates. This could reshape our understanding of how terrestrial ecosystems evolved during the Permian period.’ These insights show how Tanyka fits into a broader trend of reevaluating assumptions about early vertebrate diets.

The Broader Trend: Revisiting Assumptions About Early Vertebrates

The Tanyka discovery fits into a trend of reevaluating assumptions about early vertebrate diets. Recent studies, like those in Science Advances (2025), suggest herbivory in tetrapods may have started 10–15 million years earlier than thought. ‘The grinding structures in Tanyka suggest plant-eating adaptations were more widespread among early vertebrates,’ says Dr. Roger Smith. ‘This could reshape our understanding of how terrestrial ecosystems evolved during the Perm, period.’ This finding has implications for understanding biodiversity through geological time, especially in regions like Gondwana where many key transitions remain poorly understood.

The Mystery of the Missing Skeleton

Despite the jaw fossils, Tanyka‘s full skeleton remains unknown. ‘We found these jaws in isolation, and they’re really weird, and they’re very distinctive,’ says co-author Jörg Fröbisch. ‘Until we find one of those jaws attached to a skull or other bones that are definitively associated with the jaw, we can’t say for sure that the other bones we find near it belong to Tanyka.’ This highlights the challenges of reconstructing ancient species from fragmented remains, even with multiple specimens. The absence of a complete skeleton shows the limitations of paleontological research and the need for continued exploration in underexplored regions.

“'This is the first clear evidence of a stem tetrapod capable of grinding vegetation,' says Pardo. 'It challenges the assumption that early vertebrates were exclusively carnivorous.'”

The Significance of a ‘Living Fossil’

Tanyka amnicola exemplifies a ‘living fossil’—a species retaining traits from an ancient lineage long thought extinct. ‘This animal was a relic of an older world, surviving in a niche that had already been occupied by more advanced tetrapods,’ says Dr. Martha Richter of the Natural History Museum. ‘Its existence suggests evolutionary lineages can persist in isolated environments for millions of years, adapting slowly rather than undergoing rapid change.’ This finding has implications for understanding biodiversity through geological time, especially in regions like Gondwana where many key transitions remain poorly understood.

The Role of Brazil in Paleontological Discovery

Brazil’s Pedra de Fogo Formation has become a key site for understanding Permian ecosystems. ‘This region is one of the few places where we can study the transition from aquatic to terrestrial life in such detail,’ says Dr. Claudia Marsicano. ‘The discovery of Tanyka underscores the importance of continued exploration in the Global South, where many key evolutionary transitions remain poorly understood.’ This highlights a broader trend in paleontology toward diversifying research locations beyond North America and Europe. The discovery of Tanyka underscores the value of underexplored regions in uncovering evolutionary transitions and expanding our understanding of ancient ecosystems.

The Future of Tetrapod Research

The Tanyka discovery is likely to spur new research into early tetrapod diets. ‘We’re already planning to analyze other fossils from the same region for similar features,’ says Dr. Juan Carlos Cisneros of the Federal University of Piauí. ‘This could lead to the identification of more herbivorous species, which would fundamentally change how we view the evolution of vertebrate diets.’ Such research may also shed light on the broader ecological roles of these ancient creatures in their environments. The study of Tanyka represents a significant milestone in understanding the evolutionary history of vertebrates, challenging long-held assumptions and highlighting the importance of continued paleontological research in underexplored regions.