In their influential JVP paper, DeBraga and Reisz (1996) nested the tiny, round-head Acleistorhinus (Fig. 1) with the much larger flat-head, Lanthanosuchus (Fig.1 ). They erected the clade Lanthanosuchoidea and defined it as the most recent common ancestor of Lanthanosuchidae and Acleistorhinus. They also defined “Parareptilia” and “Ankyramorphorpha,” none of which makes any sense in the large reptile tree.
Well, one look at these taxa and their closest kin on the large reptile tree falsifies that relationship rather neatly. The details do too.
Parareptilia (Olsen 1947)
We talked about the uselessness of the paraphyletic clade “Parareptilia” before. DeBraga and Reisz (1996) defined it as the most recent common ancestor of millerettids, Acleistorhinus, lanthanosuchids, Macroleter, Procolophonia and all of its descendants. According to the large reptile tree that most recent common ancestor is a sister to Romeria primus, just two nodes away from the most basal reptile known, Cephalerpeton. Delete Procolophon from this list and you get a most recent common ancestor close to the RC14 specimen of Milleretta (Fig. 1). This definition includes all living lizards and snakes as well, so many parareptiles are actually reptiles. Evidently the definition was formulated at a time when all “parareptiles” were thought to have been monophyletic and extinct. That’s no longer the case.
DeBraga and Reisz (1996) defined “Ankyramorpha” as the most recent common ancestor of Procolophonia, Macroleter, Lanthanosuchidae, Acleistorhinus and all its descendants. Unfortunately, according to the large reptile tree, that definition includes the exact same taxa as Parareptilia. Dropping millerettids doesn’t change a thing.
DeBraga and Reisz (1996) defined “Lanthanosuchoidea” as the most recent common ancestor of Lanthanosuchidae and Acleistorhinus. In the large reptile tree that taxon is Milleretta RC14, so sans Procolophon, this clade is the same as the two previous ones since the two defining taxa are in separate clades. Lanthanosuchus belongs with Romeriscus and Macroleter. All have a wide flat skull and several other defining traits. Acleistorhinus belongs with Milleretta RC14 and Eunotosaurus (Fig. 1).
DeBraga and Reisz (1996) analyzed the relationships of Acleistorhinus using 8 taxa and 60 characters. With such a short taxon list they obviously presupposed where Acleistorhinus would nest prior to creating their inclusion set. Their Procolophonia included procolophonids, pareiasaurs and turtles. These are paraphyletic in the large reptile tree (now 338 taxa and growing). Their Millerettidae included Milleretta, Millerosaurus and Milleropsis. These are also paraphyletic. Now Millerettidae includes only Milleretta and desendants (listed above), and no longer includes Millerosaurus and Milleropsis. Those nest on the opposite branch of the Reptilia, the new Archosauromorpha, among the protodiapsids.
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