FGFR2 and Apert syndrome: Covariation analyses of skull regions defined by alternative developmental criteria to partition the skull, such as the embryological origin (neural crest/mesoderm derived bones) or the mode of ossification (endochondral/intramembranous ossification) did not reveal any significant effects of FGF/FGFR alteration on patterns of skull morphological integration in Fgfr2+/S252W and Fgfr2+/P253R Apert syndrome mouse models (Supporting Information S2).