- Response: Commentary: A Reassessment of the Taxonomic Position of Mesosaurs, and a Surprising Phylogeny of Early Amniotes

Mesosaur lateral temporal fenestra. (A) FC-DPV 1462, right jugal, probably of a newborn individual showing the typical triradiate structure normally associated with a temporal fenestra. (B) FC-DPV 1083, right jugal of a juvenile individual showing the same typical triradiate structure. (C) FC-DPV 2534B, partial skull of an adult Mesosaurus tenuidens showing a well-preserved temporal region. Some of the bones that delimit the lateral temporal fenestra (jugal and quadratojugal) are partly disarticulated. However, the jugal displays the typical triradiate structure commonly associated with the presence of a temporal fenestra. (D) Schematic drawing of the FC-DPV 2534B left postorbital region as it was preserved, showing the jugal and quadratojugal partially disarticulated. (E) Schematic reconstruction of the possible natural anatomical configuration of the FC-DPV 2534B left postorbital region. The jugal-postorbital contact and the position of the quadratojugal relative to the jugal are approximate given that the skull bones were compressed by sediment deposition, disrupting their original three dimensional arrangement. However, the proposed configuration is the most plausible one given the morphology observed in other specimens, and the general anatomy of the bones in question. Scale: (A,B) 5 mm; (C) 10 mm.