this definition. In 2002, Heckert and Lucas defined Aetosaurinae as "a stem-based taxon containing all taxa more closely related to Aetosaurus than to the last common ancestor of Aetosaurus and Desmatosuchus". The 2012 study placed Aetosaurus at the base of the stagonolepidid clade, with traditional aetosaurine taxa placed in successively more derived positions. In the analysis, these taxa are actually more closely related to Desmatosuchus than to Aetosaurus. Thus, under Heckert and Lucas's definition Aetosaurinae might be restricted to only Aetosaurus itself. Another finding of this study was that Aetosauroides lies outside Stagonolepididae. If this phylogeny is correct, Stagonolepididae and Aetosauria would not be equivalent groupings, and Aetosauroides would be the first non-stagonolepidid aetosaur. The following cladogram simplified after an analysis presented by Devin K. Hoffman, Andrew B. Heckert, and Lindsay E. Zanno. In 2016, William Parker conducted a new phylogenetic analysis of the Aetosauria, proposing an alternative hypothesis of aetosaur relationships. Below is the cladogram: Origin and evolution Although aetosaurs are known exclusively from the Late Triassic, their currently accepted position in archosaur phylogeny indicates that they originated from more basal pseudosuchian archosaurs in the Early or Middle Triassic. Given that aetosaurs are highly specialized with many anatomical features not seen in other pseudosuchians, the group's evolutionary origins are poorly understood. The recent discovery of complete specimens of the Late Triassic pseudosuchian Revueltosaurus callenderi indicate that it may have been close to the ancestry of aetosaurs. Several phylogenetic analyses place it as the sister taxon or closest relative of Aetosauria. Like aetosaurs, Revueltosaurus has two rows of paramedian osteoderms along its back and, in the cheek region of the skull, a maxilla that fits into a groove of the jugal bone. One phylogenetic analysis places Turfanosuchus dabanensis, a Middle Triassic pseudosuchian, as the sister taxon of Revueltosaurus and Aetosauria, potentially making it the earliest known "stem aetosaur" ("stem" meaning that it lies on the branch that includes aetosaurs, but is not itself an aetosaur). However, other studies have considered Turfanosuchus part of a different family of pseudosuchians, the gracilisuchids. In 2012 another "stem aetosaur" was described from the Middle Triassic Manda Beds of Tanzania. It differs from other Middle Triassic pseudosuchians in having a long skull, a small antorbital fenestra that fits into a large antorbital fossa in front of the eye socket, sharp and curved teeth, and osteoderms covering much of its body. Like aetosaurs and Revueltosaurus, it