essentially concealed in dorsal view and whose anterior margin only slightly emarginates the skull roof and has wide squamosal-postorbital bars." Hunt and Lucas also extended Colbert and Gregory's analysis that Redondasaurus was the most derived North American phytosaurs, as: "Phytosaurs show an evolutionary trend to displace ventrally the posterior portion of the midline of the skull roof. Redondasaurus represents the most advanced development of this character." Additional diagnostic criteria were introduced in 2012 by J. Spielmann and S.G. Lucas. These include: Reduced antorbital fenestra A prominent pre-infratemporal shelf A septomaxilla forming the anterolateral half of the external naris Thickened rim of the orbit Inflated posterior part of nasal Thickened dorsal osteoderms Historically, studies of Redondasaurus have been hampered by small number of specimens available, of which only four skulls were recognized in literature. Recently, several Norian-Rhaetian phytosaur skulls have been referred to Redondasaurus, which has brought the number of recognized skulls to ten. These new specimens encompass a range of sizes from hatchlings to adults and possibly include the first evidence of sexual dimorphism in the taxon. Sexual dimorphism within Redondasaurus was also recognized by J. Spielman and S.G. Lucas on May 11, 2012, at the 64th Annual Meeting of the Geological Society of America. Disagreement on the validity of Redondasaurus emerged 1995, when Long and Murry did not accept it and referred to the specimen as Pseudopalatus pristinus instead. The reason for this may have been that the type specimen of Redondasaurus is missing the entire narial area, left side of its snout, the anterior two thirds of the right premaxilla, and most of its palate. In addition to this, the term used by Savage to describe the first specimen found in 1939, Machaeroprosopus, continues to be used by some scholars in place of Redondasaurus as the genus name. Hungerbühler et al. argued in 2013 that Redondasaurus should be regarded as a junior synonym of Machaeroprosopus because: Upon a comparison of cranial characters, Machaeroprosopus lottorum is found to bridge the morphological gap between Redondasaurus and Machaeroprosopus in such a way that the distinction becomes arbitrary. According to cladistic analysis, it is unlikely that Redondasaurus is in a basal position compared to other North American pseudopalatine phytosaurs. For R. gregorii and R. bermani to be sister taxa, three additional steps would be necessary for forming a phylogenetic tree. This is the case even if the rostral crest, used by Lucas