Regarding to the dermatocranium, the pterygoid starts to ossify (Table 2).
In the dermatocranium, besides the pterygoid, the dentary starts to ossify in the anterior region of Meckel's cartilage.
In relation to the dermatocranium, other bony elements start to ossify; these include the prefrontal, the frontal, the parietal, the supratemporal, the palatine, the dentary and the surangular (Table 2).
Regarding dermatocranium, in this stage all dermal bones are present (Table 2).
Regarding dermatocranium, all bony elements are notably more developed than the stage before except of the frontal and parietal.
In the dermatocranium, frontal bones are not fully differentiated in its posterior region yet.
Also, contact between paraoccipital process and the dermatocranium
, which was previously scored as unknown, was scored as absent (67:4) for Mesosauridae, Eunotosaurus, and Belebey, and changed from '1' (to squamosal and supratemporal) to '4' (absent) for Millerettidae.
The squamosal, pterygoid and maxilla are the first elements of the dermatocranium to begin ossification, which occurs in stage 16 (Figure 3B).
Sheil and Greenbaum (2005) suggest that the bones of the dermatocranium were grouped into elements of the palatum (pterygoid, vomer and palatine), maxillary arch (premaxilla, maxilla, jugal, quadratojugal and squamosal) and the roof of the cranium (prefrontal, postorbital, frontal and parietal).
The bones of the dermatocranium and the mandible are the first to begin the ossification process: squamosal, pterygoid, maxilla, dentary, coronoid, supra-angular and branchial horn I in stage 16, the frontal, jugal, postorbital, parietal, premaxilla and prefrontal in stage 17, and the palatine and quadratojugal in stage 19.