Thecodonts (“socket teeth”) were once thought to be a group living from the Late Permian to the end of the Triassic period—a division within the archosaurs that eventually gave rise to the dinosaurs, and perhaps crocodiles, birds, and pterosaurs. It is now considered an obsolete term—and there are definite reasons why.

Just like many fields of science, the study of early dinosaurs constantly changes—not to mention that differences in opinion abound. By the mid-1980s, many scientists proposed that there was not a group called the thecodonts that evolved from the archosaurs. In fact, most scientists now believe Thecodontia as a group does not exist. Scientists cite that some of the animals listed in this group are more closely related to the crocodiles, some to dinosaurs, and some to the entire group of archosaurs. Other scientists believe that while thecodonts may not be a true group, the term was a handy way to describe certain creatures with socketed teeth within the archosaurs.