New species of “living fossil” had jaws unlike anything seen before

Fossils discovered in Brazil show that an ancient group of animals survived for much longer than realised.

When researchers digging on the edge of the Amazon rainforest came across an unusually twisted jawbone, they didn’t know what to make of it. However, after eight more turned up over the course of the dig they knew that these fossils weren’t just damaged bones but signs of a new species.

The team have now named this animal Tanyka amnicola, which roughly translates as ‘jaw living next to the river’. It’s thought that the teeth jutting out from its bent jawbone were probably used to grind up plants or small invertebrates, setting it apart from its meat-eating relatives.

Most of these animals, known as stem tetrapods, were long extinct when Tanyka lived 275 million years ago. They’d gradually been replaced by more advanced tetrapods that included the ancestors of living amphibians, reptiles, birds and mammals.

Dr Jason Pardo, the study’s lead author, says that the existence of Tanyka so late in the history of life on Earth is surprising.

“Tanyka is a little like a platypus, in the sense that it was a member of the stem tetrapod lineage that remained even after newer, more modern tetrapods evolved,” Jason says. “It was a living fossil in its time.”

“It’s a really strange animal, and the weird twist in the jaw drove us crazy trying to figure it out. But nine jaws we’ve found have this twist, including the really well-preserved ones, so it’s not a deformation. It’s just the way this animal was.”

The findings of the study were published in the journal Proceedings of the Royal Society B.

How did Tanyka eat?

In most tetrapods, the teeth in both jaws are positioned so that they face each other allowing the animal to cut, slice and grind food when they come into contact. While different species chew in different ways, they tend to follow this same basic rule.

In Tanyka, however, things were different. The lower jaw twists outwards as it runs from back to front so that some teeth point out and to the sides. Meanwhile, the inside of the jawbone is lined with tiny teeth known as denticles that would have been used for grinding.

While Tanyka’s upper jaw hasn’t been found, it’s likely that the teeth and denticles were arranged in a similar way. The denticles in both jaws would have been able rub against each other to grind down foods such as tough plant matter or the hard exoskeletons of invertebrates.

It’s such an unusual way of processing food that the team couldn’t immediately identify what kind of animal Tanyka was. Dr Martha Richter, one of our Scientific Associates that co-authored the paper, says that she was “intrigued” by the structure of the jaws.

“At first, we wondered if these fossils might be the remains of a fish,” Martha recalls. “It was only once the fossils were properly prepared in the lab that the true nature of Tanyka was clearly revealed to us.”

“By comparing its anatomical traits to the characteristics of known species from across hundreds of millions of years, we found that this animal was actually a primitive tetrapod after all.”

While it’s uncertain what Tanyka looked like, the researchers think that it was probably similar to a salamander with a longer snout. Other fossils have been found near Tanyka’s jawbones that might represent other parts of the body, but it’s not certain they came from the same animal.

Finding the jaws associated with other bones would help the team be confident what this animal looked like.

Tetrapod survivors

When Tanyka was alive during the Early Permian Period, almost all of the world’s landmasses were united into one enormous supercontinent known as Pangaea.

For a long time it was assumed that stem tetrapods had largely died out by this point. An event known as the Carboniferous rainforest collapse caused the widespread extinction of these animals as the moist environments they relied on gave way to drier habitats.

However, the discovery of Tanyka builds the case that not all stem tetrapods were affected in the same way. While animals in the northern part of Pangaea appear to have gone extinct, those in the south might have been able to survive due to differences in the climate across the large continent.

Tanyka may also have had adaptations that allowed it to survive in more arid conditions. The area where it lived would have been hot and seasonally dry, similar to the southwest United States today, suggesting that it might have been better able to cope with change.

Finding out why these southern species lived when others died out will mean finding more of their fossils. Those from South America, Africa, Australia and Antarctica will be particularly important to see if the conditions there helped these animals to survive.