ABSTRACTTooth attachment and implantation are two classical descriptors of dental anatomy. Tooth attachment distinguishes between teeth that are either fused to the jaw by bone, or suspended within a socket by a periodontal ligament. Tooth implantation describes the geometry of this attachment and has been broadly divided into acrodonty, pleurodonty, and thecodonty. Among extant amniotes, only mammals and crocodilians are considered truly thecodont, because they possess a complex attachment system that includes a periodontal ligament and true tooth sockets. These two amniote groups diverged from a common ancestor over 300 million years ago and are thought to have evolved thecodonty independently. This view has recently come under a great deal of scrutiny with the discovery of complex tooth attachment systems, including the presence of a ligamentous tooth attachment in numerous non-mammalian, non-crocodilian amniotes. This has spurred debate and inconsistencies over the conventional usage of tooth attachme...