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The skull of Teyujagua paradoxa. From Pinheiro et al., 2016.

Paleo Profile: Teyú Yaguá

Do a Google Image search for the word “Triassic” and you’re going to see variations of the same scene over and over again. Svelte little dinosaurs snap and squawk around an ancient lake or river, with the also-rans of their era – such as the armored aetosaurs and superficially-crocodile-like phytosaurs – shuffling through the undergrowth and basking at the water’s edge. Such vignettes are classic Triassic imagery, and yet they’re only a narrow view of one part of the opening chapter in the Age of Reptiles triology. There’s far more to the Triassic story than Coelophysis and its neighbors, with the latest wrinkle to the tale arriving in the form of a beautiful skull found in Brazil.

The fossil, described by paleontologist Felipe Pinheiro and colleagues, was that of an archosauromorph. This was a line of reptiles that first evolved back in the Permian, when the protomammals held sway, and underwent explosive diversification during the Triassic, eventually sprouting branches that would include dinosaurs, pterosaurs, and crocodiles.

Named Teyujagua paradoxa by the researchers, the 251 million year old animal lived just before the great reptilian radiation really took off. So while not necessarily the ancestor of the various lineages that would come later, Pinheiro and coauthors point out that the skull of Teyujagua is a significant part of the story given that it exhibits some characteristics of older forms of reptiles as well as novelties that would come to mark the “ruling reptiles” such as serrated teeth and an opening in the sidewall of the lower jaw. When you look at the skull of Teyujagua, you’re looking at a face that helped set evolutionary trends from the dawn of the Triassic until today.

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A close-up of Teyujagua. From Pinheiro et al., 2016.

Fossil Facts

Name:Teyujagua paradoxa

Meaning: The genus was named after Teyú Yaguá, a dog-headed lizard in Guarani mythology, while paradoxa underscored the “unusual” combination of characteristics.

Age: Around 251 million years ago.

Where in the world?: Southern Brazil.

What sort of critter?: An archosauromorph, or an ancient member of the lineage that includes dinosaurs, pterosaurs, crocodiles, and their relatives.

Size: The skull is about four and a half inches long.

How much of the creature’s body is known?: A nearly-complete skull and several neck vertebrae.


Pinheiro, F., França, M., Lacerda, M., Butler, R., Schultz, C. 2016. An exceptional fossil skull from South America and the origins of the archosauriform radiation. Scientific Reports. doi: 10.1038/srep22817

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