In a dry riverbed deep within a forest near the Amazon in Brazil, paleontologists discovered the fossilized jawbone of a previously unknown ancient animal. As their excavation continued, the team found eight more identical jaw bones, each about six inches long. However, they did not find any additional bones that could be clearly matched to the complete skeleton.
Still, these isolated jaws revealed something remarkable. These fossils belonged to a species that lived approximately 275 million years ago and would have been considered a “living fossil” even in its time. The jaws were also highly unusual with a curved shape. Some teeth protruded outward and to the sides, while rows of smaller teeth lined the inner surfaces. This structure suggests that this animal may have been the first of its kind to grind plant material.
Naming a strange new species
In a study published in Proceedings of the Royal Society BResearchers formally described the species and named it Tanyca amnicola. The name Tanyaka comes from the indigenous Guarani language and means “jaw”, while Amnicola translates to “living by the river”.
“Tanyaka is from an ancient lineage that we didn’t know was alive until all this time, and it’s also a very strange animal. It has this weird bend in the jaw that has driven us crazy trying to understand it. We’ve been scratching our heads over it for years, wondering if it was some kind of deformity,” says study lead author Jason Pardo, who worked on the project during 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 this really, really well-preserved one. So it’s not a deformity, it’s just the way the animal was made.”
an ancient branch of tetrapods
Tanyka belongs to a broad group of vertebrates known as tetrapods, which includes animals with all four limbs and a backbone, such as reptiles, birds, mammals and amphibians. The oldest tetrapods, called stem tetrapods, eventually split into two major branches. One group evolved to lay eggs on land, giving rise to reptiles, birds, and mammals. The second group continued to lay eggs in water, giving rise to modern amphibians such as frogs and salamanders.
Even after this split, some stem tetrapods continued to exist along with their more recently evolved relatives. Tanyaka was one of these holdovers from the old lineage.
A similar pattern can be seen in mammals also. Early mammals laid eggs, while later groups developed live birth. Most modern mammals reproduce by giving birth, but some species, such as the platypus, still retain the old egg-laying trait.
“In the sense that Tanyka was a remaining member of the stem tetrapod lineage, even after newer, more modern tetrapods evolved, Tanyka is 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 Vilnius University in Lithuania.
What did Tanyka look like?
Much is unknown about Tanyka, especially her full body size. “We found these jaws isolated, and they’re really weird, and they’re very distinctive. But until we find one of those jaws attached to the skull or other bones that are definitely associated with the jaw, we can’t say for sure that the other bones we found near it belong to Tanyka,” says Ken Engelsky, curator of paleomammology at the Field Museum in Chicago, who did his post-doctoral fellowship there. Pardo, and co-authored a paper.
Based on comparisons with related species, researchers believe Tanyka may have resembled a salamander with a slightly longer snout. Its size is uncertain, but it is estimated that its length could be up to three feet. The surrounding rock indicates that it probably lived in freshwater environments such as lakes.
a jaw designed for grinding plants
Although the rest of its body is still a mystery, the jaw provides a clear clue to how Tanika fed.
If you run your tongue over your bottom teeth, you can feel how they point upward toward the roof of your mouth. This system was completely different in Tanyaka. Its lower jaw was bent in such a way that the teeth were protruding outwards instead of upwards. At the same time, the inner surface of the jaw, which faces the tongue in humans, was oriented upward.
This inner surface was covered with tiny teeth, called denticles, which created a rough grinding area similar to a cheese grater. Scientists believe that the structure of the upper jaw was probably similar.
“We expect that the teeth in the lower jaw would be rubbing against the same teeth in the upper part of the mouth. The teeth would be rubbing against each other, creating a relatively unique way of feeding,” says Pardo.
This type of tooth-to-tooth grinding is typically associated with animals that process plant material. “Based on its teeth, we think Tanica was a herbivorous animal, and that it ate plants at least some of the time,” says paper author Juan Carlos Cisneros, of the Federal University of Piauí (UFPI) in Brazil. The researchers note that this is surprising, as most stem tetrapods are known to be carnivorous.
Filling gaps in ancient ecosystems
The discovery of Tanyka helped scientists better understand life during the early Permian period. About 275 million years ago, the area that is now Brazil was part of Gondwana, a supercontinent that included South America, Africa, Australia, and Antarctica. Fossils from this time and place are relatively rare compared to areas of the Global North.
“The Pedra de Fogo Formation in Brazil is one of the only windows we have into the animals of Gondwana during the early Permian period of Earth’s history, and Tanyka is telling us how this community really worked, how it was structured, and who was eating what,” says Angielczyk.
Study co-authors were Jason Pardo (Field Museum, Vilnius University), Claudia Marsicano (Universidad de Buenos Aires, CONICET), Roger Smith (Iziko South African Museum, University of the Witwatersrand Johannesburg), Ken Angelski (Field Museum), Jörg Frobisch (Museum für Naturkunde – Leibniz-Institut für Physiology or Medicine). Evolutions- und Biodiversitatsforschung), Christian Kammerer (North Carolina Museum of Natural Sciences), and Martha Richter (Natural History Museum, London).