Thecodontia (thecodonts) ‘Tooth-in-socket’ reptiles, and the most primitive order of the Archosauria (‘ruling reptiles’), ranging from the Upper Permian to the Upper Triassic. They were ancestral to the dinosaurs, pterosaurs, and crocodiles. One of the first thecodonts was Thecodontosaurus browni which flourished during the Early Triassic. It grew to 2–3 m in length and had a small head and neck. Essentially it was a quadruped, but it could walk on its hind legs.

Thecodontia (class Reptilia, subclass Archosauria) An order of ‘tooth-in-socket’ (i.e. thecodont) reptiles, and the most primitive of the archosaurs, that ranged from the Upper Permian to the Upper Triassic. Thecodontosaurus browni was one of the first of the group. It grew to 2–3 m in length and had a small head and neck. Essentially it was a quadruped, but it could walk on its hind legs. The Thecodontia were ancestral to the dinosaurs, pterosaurs, and crocodiles. Apart from a limited number of primitive features in the skull, Euparkeria, a thecodont from the Lower Triassic, is a likely ancestor for most archosaurian stocks. It was a small reptile, only 60–100 cm in length.