When the identification of a fossil animal is completely based on a single bone, the design of the bone is important. Another Permian animal with no complete body akin only to the low jaws has a mechanical arrangement quite unlike that of nearly all other vertebrates with four limbs: instead of its teeth being turned inwards to form a typical bite, they are turned outwards, as though the jaws were to grate instead of grab.
The species, Tanyka amnicola, inhabited approximately 275 million years ago, and was an archaic species in the tetrapods- four limbed vertebrates containing modern reptiles, birds, mammals and amphibians. But Tanyka was not one of the more recognizable divisions to spread on land and water through the Permian. The animal itself seems to belong to a older, more ancient, “stem”-tetrapod group which scientists previously believed had become extinct, and is thus a holdout, a fossil of an evolutionary experiment, in a time of experimentation.
The species was found by scientists formed in nine fossilized lower jawbones that were approximately 6 inches (15 centimeters) long and found in a dry riverbed in northeastern Brazil. The repetition was important: the same funny turn was re-employed in the same specimens, time and again, even in the most wonderfully preserved specimens. As author Jason Pardo put it, “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.”
That turn alters the geometry of feeding. In the vast majority of tetrapods, the lower jaw is turned upward to meet the upper jaw in a mere hinge-and-bite/action. In Tanyka the lower jaw turned in such a way that the main teeth stuck outwards and slightly on the side. What is stranger still, the inner surface of the jaw, or rather that which would in human beings lead to the tongue of the human being, was directed vertically upwards, and covered by thick, tooth-like denticles, which made it a grinding field. The organization indicates that rather than puncture and tear, contact surfaces must have been used to crush or shred with the mouth depending on the relative orientation of matching structures of the upper jaw.
The rocks that contained the fossils indicate lake or slow-water environments, which are favourable towards an aquatic lifestyle. The rest of the body has not as yet been established, although again comparison with close relatives indicates a salamander-like shape, with a longer snout and a possible overall length of up to about 3 feet (91 centimeters). The name is based on language and place: “Tanyka” is an Indigenous Guaranin word of the translation of “jaw” and “amnicola” is an indicator of an animal living on a river.
The jaws come into special prominence in diet. The denticles in a rasping pattern are widely regarded to be used on harder material, and the researchers believe that Tanyka was probably feeding on small invertebrates and may have fed on plants. In case plant-eating was its normal practice, it would put herbivory or omnivory in a surprising branch of the tetrapod tree, most tetrapods on the stems being carnivores in broad sense. That difference is further emphasized in conjunction with other Early Permian data that terrestrial food webs were already organized in terms of specialized functions, such as direct tooth impressions on juvenile Diadectes of predators on large herbivores on land.
The value of Tanyka is also geographic. The fossil record of early Permian vertebrates of what is now Gondwana is relatively sparse, the Pedra de Fogo Formation in Brazil being one of the few consistent gaps into that ecosystem in the south. The drawing, with jaws alone, is not a complete one but this is certainly the design: a crooked-sided, toothed engine, which suggests how differently the early tetrapods might have tackled the problem of eating.
