Evolution of dermatocranial elements.
(A) Traditional scheme of the dermal skull roof, based on the head segmentation scheme of Jollie (1981) . (B) Schematized prototype of the arthrodire dermal skull roof as suggested by Heintz (1932) . Homologies between various dermal elements in B and F are indicated by color. (C-F) Dermatocranium of Eustenopteron
(C and D) and Entelognathus
(E and F), lateral (C and E) and dorsal (D and F) views. Thick red lines represent lateral lines that correspond to patterns of some dermal elements. Presumed homologous dermal elements are shown in the same color in C and E and the left halves of D and F. On the right side of D and F, neural crest- and mesoderm-derived elements are differently colored according to assumptions that the crest–mesoderm interface is primarily found between the frontal and parietal bones (as in the mouse) and that postparietal homologues are consistently derived from the neural crest in sarcopterygians (including tetrapods). C-F, redrawn from .