Order Rhynchosauria
Order Trilophosauria
Order Prolacertiformes
Division Archosauriformes
Division Archosauria
Archosauromorpha (Greek for "ruling reptiles form") are a diverse group or Infraclass of diapsid reptiles that first appeared during the late Permian, but only became common during the Triassic. Included under this heading are Rhynchosauria , Trilophosauridae , Prolacertiformes , Archosauriformes, and, tentatively, the Choristodera . While superficially these reptiles are all pretty different (and indeed at one time were even included in different subclasses - the Trilophosaurs were considered Euryaspids , and the Rhynchosaurs lepidosaurs and included in the same order as the tuatara - they are actually united by a number of small details in the skull and skeleton, which show that they form a monophyletic clade that descended from a single common ancestor.
Of the five taxa mentioned above, the first three died out at or prior to the end Triassic extinction, the Choristoderans continued as a minor group until the Miocene, and the Archosauriformes were important elements in early Triassic environments, before giving rise to the even more successful Archosauria.
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