Thecodonts are extinct reptiles that lived during the Mesozoic era. These reptiles were characterized by their unique dental structure, which included teeth that were set deeply in the jawbone. Synonyms for Thecodonts include primitive archosaurs, basal archosaurs, and early archosaurs. These terms refer to the evolutionary position of Thecodonts as a primitive group of reptiles that gave rise to the more advanced archosaurs such as crocodiles, dinosaurs, and birds. Other synonyms for Thecodonts include phytosauromorphs, proterosuchids, and erythrosuchids, which describe specific subgroups within this extinct group of reptiles. Though they are no longer with us, Thecodonts are an important part of our understanding of the evolution of reptiles and other animals.