Tanyka amnicola is a newly identified ancient tetrapod known from unusual twisted jawbones adapted for grinding plants. This rare herbivorous “living fossil” helps scientists better understand early evolution and ecosystems in Gondwana.
In a dry riverbed in Brazil, deep within a forest near the Amazon, paleontologists uncovered a fossilized jawbone from an unknown ancient animal. Continued fieldwork revealed eight more similar bones, each about six inches (15 cm) long. However, no additional remains were found that could be confidently assembled into a complete skeleton.
Even with only jawbones, researchers determined the fossils belonged to a species that would have been considered a “living fossil” during its time, around 275 million years ago. The jaws showed an unusual twist, with some teeth angled outward and sideways, while many smaller teeth lined the inner surface. This structure suggests these animals were among the earliest vertebrates capable of grinding plant material.
In a study published in Proceedings of the Royal Society B, scientists introduced the new species as Tanyka amnicola. The name Tanyka comes from the Indigenous Guaraní language and means “jaw,” while amnicola translates to “living by the river.”
Evolutionary Background of Tetrapods and the Concept of Living Fossils
“Tanyka is from an ancient lineage that we didn’t know survived to this time, and it’s also just a really strange animal. The jaw has this weird twist that drove us crazy trying to figure it out. We were scratching our heads over this for years, wondering if it was some kind of deformation,” says Jason Pardo, the study’s lead author, who worked on this project as part of his post-doctoral fellowship at the Field Museum in Chicago. “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 belongs to a broader group known as tetrapods, which are four-limbed vertebrates that include reptiles, birds, mammals, and amphibians. Early in their history, stem tetrapods split into two major groups. One group evolved to lay eggs on land, while the other continued laying eggs in water.
Modern reptiles, birds, and mammals descend from the lineage that developed watertight eggs suited for land. Amphibians such as frogs and salamanders trace back to the group that remained dependent on moist environments for reproduction.
Survival of Ancient Lineages and Modern Comparisons
Even after this evolutionary split, some stem tetrapods persisted. Tanyka was one of these survivors.
Older evolutionary lineages can continue alongside more recently evolved groups. Mammals provide a clear example. Early mammals laid eggs, but later species evolved live birth. While most mammals today reproduce this way, a few, such as platypuses, still belong to the older egg-laying lineage.
“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. It was a living fossil in its time,” says Pardo, who is now a research associate at the Field Museum while working on a postdoctoral fellowship through the University of Vilnius in Lithuania.
Physical Characteristics and Ongoing Scientific Uncertainty
Much about Tanyka remains unknown, especially its overall body structure. “We found these jaws in isolation, and they’re really weird, and they’re very distinctive. But 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,” says Ken Angielczyk, a curator of paleomammalogy at the Field Museum in Chicago, who served as Pardo’s advisor during his post-doctoral fellowship there and a co-author of the paper.
“We can say, by comparison with close relatives, that Tanyka might have looked kind of like a salamander with a slightly longer snout,” says Pardo. Its size is uncertain, but estimates suggest it could have reached up to three feet (0.9 meters) in length. Fossil evidence also indicates it likely lived in lake environments.
Even without a full skeleton, the jaw alone reveals how unusual this animal was.
Unique Jaw Structure and Feeding Adaptations
If you run your tongue across your lower teeth, you will notice they face upward toward the roof of your mouth. In Tanyka, the lower jaw was twisted so the teeth pointed outward to the sides instead. At the same time, the inner surface of the jaw, which faces the tongue in humans, was oriented upward. This surface was covered in small teeth called denticles, forming a rough grinding surface similar to a cheese grater.
Although the upper jaw has not been found, scientists believe it likely had a matching structure. “We expect the denticles on the lower jaw were rubbing up against similar teeth on the upper side of the mouth. The teeth would have been rasping against each other in a way that’s going to create a relatively unique way of feeding,” says Pardo.
Teeth adapted for grinding are typically associated with plant consumption. “Based on its teeth, we think that Tanyka was a herbivore and that it ate plants at least some of the time,” says Juan Carlos Cisneros, an author of the paper at the Federal University of Piauí (UFPI) in Brazil. This is unusual because most stem tetrapods are believed to have been carnivorous.
Importance of the Discovery for Gondwana’s Fossil Record
The discovery of Tanyka helps fill important gaps in the fossil record. Around 275 million years ago, present-day Brazil was part of the supercontinent Gondwana, which also included regions that are now South America, Africa, Australia, and Antarctica. Compared to fossil sites in the Northern Hemisphere, relatively few animals from this period have been found in Gondwana.
“The Pedra de Fogo Formation in Brazil is one of the only windows we have into Gondwana’s animals during the early Permian Period of Earth history, and Tanyka is telling us about how this community actually worked, how it was structured, and who was eating what,” says Angielczyk.
Reference: “An aberrant stem tetrapod from the early Permian of Brazil” by Jason D. Pardo, Claudia A. Marsicano, Roger Smith, Juan Carlos Cisneros, Kenneth D. Angielczyk, Jörg Fröbisch, Christian F. Kammerer and Martha Richter, 1 March 2026, Proc Biol Sci.
DOI:10.1098/rspb.2025.2106
Never miss a breakthrough: Join the SciTechDaily newsletter.
Follow us on Google and Google News.