Archosauromorph

Disputed members

Apart from these four groups, Archosauromorpha is sometimes considered to encompass several additional groups of reptiles. One of the most common additions is Choristodera, a group of semiaquatic reptiles with mysterious origins. Although choristodere fossils are only known from the Jurassic through the Miocene, it is theorized that they first appeared during the Permian alongside the earliest archosauromorphs. Choristoderes share numerous otherwise unique traits with archosauromorphs, but they share an equal or greater number of unique traits with lepidosauromorphs as well, so there is still some debate over their inclusion within either group. The chameleon- or tamandua-like drepanosaurs are also semi-regularly placed within Archosauromorpha, although some studies have considered them to be part of a much more basal lineage of reptiles. The aquatic thalattosaurs and gliding kuehneosaurids are also irregularly considered archosauromorphs.