Teyujagua

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Teyujagua is an extinct, small archosauromorph reptile from Brazil that lived in the Early Triassic period. The only described species is Teyujagua paradoxa. It is known from a exceptionally well-preserved skull and a few neck bones, and it was probably a carnivore that hunted near water. The animal may have grown up to about 1.5 meters (4.9 feet) long and likely looked a bit like a crocodile.

Key facts in simple terms:
- Time and place: Early Triassic, Brazil, especially the Sanga do Cabral Formation in the Paraná Basin.
- Size and mix of traits: A small predator with a mix of features that are primitive for archosauromorphs and more advanced traits found in archosauriformes.
- Skull and teeth: The skull is nearly complete and shows a long, broad snout with serrated teeth. It has a forward-facing external mandibular fenestra, an unusual feature beneath the eye when the jaw is closed. Teeth are heterodont (different shapes), up to 15 large maxillary teeth, and the teeth are set in sockets (thecodont) rather than fused to bone.
- Primitive and derived traits: It lacks an antorbital opening (a primitive feature) and has an open lower temporal bar, but it also has archosauriform-like traits such as serrated teeth and a visible mandibular fenestra.
- Lifestyle clues: The eyes and nose placement suggest semi-aquatic habits; the teeth indicate a hypercarnivorous diet. However, the animal’s vision would have been more side-facing than deeply binocular, hinting at a primarily terrestrial, sight-oriented hunter.
- Discovery and name: The holotype is UNIPAMPA 653, found in 2015 and described in 2016 by Pinheiro and colleagues. The genus name Teyujagua comes from Guaraní mythology, referring to a fierce lizard or dog-like lizard, and paradoxa means paradox, highlighting its mix of ancestral and derived features.
- Why it matters: Analyses place Teyujagua as a near relative of Archosauriformes, supporting a mosaic pattern of skull evolution in early archosauromorphs. It contributes to the idea of a two-phase radiation of archosauriforms—one in the late Permian and another after the Permian–Triassic extinction—helping scientists understand how key archosaur features appeared over time.