Earlier and a day before that we looked at the problems posed by Brouffia, which two earlier workers, Brough and Brough (1967) and Carroll and Baird (1972) interpreted significantly different from each other. Both sets of workers had direct access to the fossil and presumably looked at it with binocular microscopes. The two authors did not agree on the placement of the pineal opening, the presence or absence of intertemporal bones and several other distinctions, including the number of sacrals present. Ironically, the Brough and Brough team found an intertemporal and thus determined the specimen was pre-reptilian, but then decided there were two sacrals present, which is a reptilian trait. The Carroll and Baird team found no intertemporal, but only one sacral, a pre-reptilian trait.
Today we’ll do our best to make sense of this mess without seeing the actual fossil, or even a photo of the fossil (yes, I’m peering over the abyss). Instead we’ll pull clues from the only available data, drawings (Fig. 1) by the above two studies.
The first thing I note is that neither prior study found large palatal fangs. So that puts us over the pre-reptile/reptile divide on the reptile side. The prefrontal and postfrontal just barely did not touch. That is also a reptilian trait. The Carroll and Baird (1972) study found only one sacral, but the evidence indicated the earlier Brough and Brough (1967) study was correct in finding two sacrals. The posterior rim of the squamosal was straight, lacking an otic notch, which is another reptilian trait.
A new reconstruction of the skull (Fig. 1) is based on the anterior data provided by Brough and Brough (1967) because the the Carroll and Baird (1972) study failed to provide data here. The posterior data is based on Carroll and Baird (1972) because it is more reptilian and we’re leaning that way due to the lack of palatal fangs, last seen in Gephyrostegus. Brough and Brough (1967) also interpreted some strange processes on the dorsal jugal that probably represent the ventral postorbital/postfrontal suture.
With the reconstruction of the skull in hand the data nested Brouffia at the most basal position in the new Archosaurmorpha branch of the large reptile tree (it’s not listed there yet, but will be before year’s end). It shares a few traits with gephyrostegids and new lepidosauromorphs that no other archosauromorph shared. I suspect that more of the palatine is hiding beneath the mandibles. The premaxilla/maxilla connection is more fragile than in any other basal reptile. Overall the skull resembles gephyrostegids and coelostegids and paleothyrids. The premaxilla dipped as in captorhinids.
I will be relaying out the appropriate pages on reptileevolution.com to make room for this key taxon at the very base of the Reptilia. This moved Cephalerpeton over to the new lepidosauromorpha, so we no longer have a single most basal reptile following Gephyrostegus.
Still looking for photos of the specimen, if available. We’ll have one more post on this series detailing some of the traits this new taxon nesting sheds light on.
As always, I encourage readers to see specimens, make observations and come to your own conclusions. Test. Test. And test again.
Evidence and support in the form of nexus, pdf and jpeg files will be sent to all who request additional data.
Brough MC and Brough J 1967. The Genus Gephyrostegus. Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences 252 (776): 147–165. doi:10.1098/rstb.1967.0006
Carroll RL and Baird D 1972. Carboniferous Stem-Reptiles of the Family Romeriidae. Bulletin of the Museum of Comparative Zoology 143(5):321-363. biodiversitylibrary