"Anatomical relationships of the jaws and chondrocranium of living hyostylic sharks based on Scyttium and Carcharhinus. (a) Lateral and corss-sectional views of the head skeleton of Scyttium with the jaws closed. (b) Dorsal view of Carcharhinus. (c) During jaw opening and upper jaw protrusion the hyomandibula rotates from a position parallel to the long axis of the cranium to a position nearly perpendicular to that axis. S, spiracle; Q, quadrate region or the palatoquadrate; H, hyomandibula; M, mandible" (from Pough et al. 1993).

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