Article: The origin and intrarelationships of Triassic capitosaurid amphibians

The status of the temnospondyl family Capitosauridae is reviewed. Only by the inclusion of the genera Mastodonsaurus and Eocyclotosaurus can this group be considered monophyletic. This view is based on a range of robust characters which in combination constitute the most parsimonious hypothesis. The traditional view that Mastodonsaurus and Eocyclotosaurus are sister taxa of Benthosuchus is demonstrated to be based on highly variable and/or homoplastic features, whose ancestral condition is moreover uncertain. The Capitosauridae encompasses the following successive sister groups: (1) various species of Parotosuchus (which do not necessarily form a monophylum); (2) the genera Eryosuchus and Mastodonsaurus (which are probably monophyletic); and (3) a range of taxa with semi-closed or entirely closed otic notches, including the genera Wellesaurus, Kupferzellia, Eocyclotosaurus, and Cyclotosaurus. The closure of the otic notch, an oft-cited trend among capitosaurs, is most easily explained to have occurred only once, namely within the more advanced capitosaurids; the stratigraphical significance of this feature is, however, very limited.