Nine jawbones pulled from a Brazilian riverbed don’t sound like much of a discovery at first. No complete skeleton. No skull. Just nine twisted pieces of bone, each about six inches long, buried in rock that’s been sitting there for 275 million years. Yet these fragments belong to a creature so strange and so anachronistic that it’s forcing scientists to reconsider what they thought they knew about early vertebrate evolution.
The animal is called Tanyka amnicola, and it shouldn’t have existed when it did. According to research published in Proceedings of the Royal Society B, this thing was essentially a fossil living in its own time, clinging to a lineage that should have been extinct millions of years before it was even born.
A Jaw That Drove Scientists Crazy
Jason Pardo, the study’s lead author, spent years staring at these jawbones trying to figure out what was wrong with them. The twist in the bone was so pronounced and so consistent across all nine specimens that he and his team couldn’t initially accept it was natural. “We were scratching our heads over this for years, wondering if it was some kind of deformation,” Pardo recalls. But there’s no deformation here. Nine samples don’t lie.
The twist isn’t just odd. It’s geometrically bizarre. In humans, your lower teeth point upward toward the roof of your mouth. In Tanyka, the entire jaw was rotated so that the teeth pointed outward to the sides instead. Meanwhile, the inner surface of the jaw, which would normally face your tongue, was oriented upward like the inside of a spoon.
This inner surface was covered with tiny teeth called denticles that formed a rough grinding surface. Think of it like a biological cheese grater.
An Herbivore When Herbivores Shouldn’t Exist
Here’s where it gets really interesting. The grinding arrangement suggests Tanyka used its teeth to process plant material. This is surprising because most stem tetrapods, the ancient group Tanyka belongs to, were carnivorous hunters. An herbivorous stem tetrapod this far back in evolutionary history doesn’t fit the expected pattern.
Juan Carlos Cisneros, one of the paper’s authors, says the evidence is clear: “Based on its teeth, we think that Tanyka was a herbivore, and that it ate plants at least some of the time.” The denticles on the lower jaw would have rubbed against similar teeth on the upper jaw, creating a rasping motion perfect for breaking down vegetation. It was a feeding strategy fundamentally different from anything else in its ecological community.
A Living Fossil Before “Living Fossils” Were Famous
Tanyka belongs to the tetrapods, the broad group that includes all four-limbed backbone animals like reptiles, birds, mammals, and amphibians. Early on, tetrapods split into two major branches. One group evolved to lay eggs on land, eventually leading to modern reptiles and birds. The other kept laying eggs in water, eventually giving rise to modern amphibians.
But here’s the thing: not all the old lineages disappeared after that split. Some ancient stem tetrapods kept existing alongside their newer, more evolved cousins. Tanyka was one of these holdovers. It was a survivor from an older chapter of vertebrate history, persisting long after newer models had already evolved.
Pardo draws a useful comparison: “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.” The platypus is a modern mammal that still lays eggs, a trait most mammals abandoned millions of years ago. Tanyka occupied a similar role in the Permian Period, 275 million years ago, representing an older way of being.
Glimpses Into a Lost World
We don’t know what Tanyka looked like beyond its jaw. Based on comparisons with related species, researchers estimate it may have resembled a salamander with a slightly longer snout, possibly reaching up to three feet in length. Ken Angielczyk, a curator at the Field Museum who advised on the research, is cautious about speculation. “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.”
The rocks surrounding the fossils suggest Tanyka lived in freshwater environments, likely lakes and rivers. These remains come from the Pedra de Fogo Formation in Brazil, one of the few windows we have into the animal communities of Gondwana, the massive supercontinent that once contained South America, Africa, Australia, and Antarctica.
Fossils from this region and era are rare compared to those from the Global North, which means Tanyka’s discovery is more than just a curiosity. Angielczyk explains why this matters: “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.”
What Remains Unknown
The problem with nine isolated jawbones is obvious: they tell us how Tanyka ate but almost nothing about how it moved, what size it really was, or how it reproduced. We’re looking at a creature through a keyhole, seeing only the mechanism of its mouth but not the animal itself. This is the reality of science sometimes. We find fragments and build theories around them, knowing full well that the next discovery might require us to revise everything.
What makes Tanyka worth the scientific effort is precisely this: it represents something we didn’t know existed. An ancient branch of vertebrate life that persisted when it shouldn’t have, that ate in ways its relatives didn’t, that survived in the ecological shadow of newer, supposedly superior competitors. It’s a reminder that evolution isn’t a single story marching toward inevitable progress but a complicated landscape where old solutions sometimes keep working long after they’re supposed to be obsolete.
The question now is whether Tanyka was unique, or whether similar creatures are waiting to be discovered in other ancient riverbeds around the world. What other evolutionary leftovers are we still waiting to find?
