The jaws of the river - Tanyka amnicola

A fascinating discovery from the Pedra de Fogo Formation, Lower Permian in Northeast of Brazil: Tanyka amnicola, a stem-tetrapod that extends the record of a lineage primarily known from the Carboniferous, and shows adaptations to a peculiar niche that exploited a herbivorous or omnivorous diet.

The name "Tanyka" comes from Guarani, local indigenous language, and the word means "jaw"; from Latin, "amnicola" means "that lives in/near the river". The fossils are all of jaws, most of them approximately 17 cm long (one of them being 25% larger), and the animal would have reached ~1 m in length.

Known from 9 jaws, Tanyka had teeth turned outwards, as if its mouth were twisted. What seemed like a deformation due to injury or fossilization proved to be a feature of the species as more and more specimens were found, some very well preserved. The strange shape is probably due to a slight rotation that the jaw makes on its own axis when opening the mouth. The posterior portion of mandible also had a curious trianglular flange pointing outwards.

In addition to the main teeth row, next to it there were remarkable pads full of denticles that would have acted like a grinder. With them, Tanyka possibly scraped and crushed algae, plants, and/or hard-shelled invertebrates, being a herbivore or omnivore. This is something super rare among amphibians, extinct or extant, and shows us how these ancient tetrapods explored unusual niches.

Tanyka is not a close relative of contemporary Permian temnospondyl amphibians, but it is part of a group of stem-tetrapods that originated in the Carboniferous, the baphetids. A lost survivor, compared to what the platypus represents for mammals today.

At the invitation of Dr. Juan Cisneros, I had the pleasure of creating the illustration for the media release of the research! In the scene, Tanyka feeds on algae and conchostracans that hide among them.

Check the paper: Pardo, J. D., Marsicano, C. A., Smith, R. M. H., Cisneros, J. C., Angielczyk, K. D., Fröbisch, J., Kammerer, C. F., & Richter, M. (2026). An aberrant stem tetrapod from the early Permian of Brazil. Proceedings of the Royal Society B: Biological Sciences. DOI: doi.org/10.1098/rspb.2025.2106

*Update 27/08/2026: The background fish were a species still under study at the time the painting was made, and they have just been officially described! Meet Nazaria limnica!