Rhynchonkos stovalli (Olson 1970 - originally Goniorhynchus stovalli but renamed by Schultze and Foreman 1981; Early Permian) was originally considered an ancestor to living caecilians but not Eocaecilia has that honor and the traits Rhynchonkos shared with caecilians are here considered convergent. Derived from a sister to Micraroter, Rhynchonkos was evidently the last in this lineage, but was a sister to Batropetes.
Distinct from Micraroter, the skull of Rhynchonkos did not have such a tall cheek emargination and the quadratojugal was deeper. The supratemporal/tabular fused to the squamosal. As in Batropetes, the occiput bulged posteriorly and was visible in lateral view. The premaxilla was not visible in dorsal view. The skull was overall narrower/longer. A small pineal opening remained. In occiput view the sutures between the fused supratemporal/ tabular/ squamosals and the postparietals diverged laterally. The teeth were smaller and sharper.
37 presacral vertebrae were present. The arch of the atlas was attached to the centrum, which bore no ribs, unlike most microsaurs, but like Ptyonius. A lumbar region of shorter ribs appeared in the posterior dorsals. The pectoral girdle was poorly ossified. The pelvis was smaller and narrower. |
