Fig. 2. Illustration of the Pomacanthus semicirculatus skull (left lateral view) based on clear-stained preparations. (A) Feeding apparatus when relaxed. (B) Suspensorium and operculum rotated, and jaws protruded. (C) Detail of protruded-closed oral jaws. Osteology labelling: an, angular; art, articular; d, dentary; hyom, hyomandibular; ihy, interhyal; iop, interoperculum; mpt, metapterygoid; mx, maxilla; op, operculum; pal, palatine; pmx, premaxilla; pop, preoperculum; ptr, ectopterygoid; q, quadrate; sop, suboperculum; supcl, supracleitrum; sym, symplectic; urohy, urohyal; lc, lachrymal; points of flexion are indicated in A between hyomandibular with nc, neurocranium (filled circle) and between the palatopterygoid complex of the suspensorium with the lateral ethmoid (open circle). Open circle in C: IMJ, intramandibular joint. Myology labelling: A1 (10% grey); A2 (50% grey, and medial to A1 and A3); A3 (30% grey), adductor mandibulae segments. LOP: levator operculi, DOP: dilator operculi, LAP: levator arcus palatini, AAP: adductor arcus palatini. Ligament labelling (all in 75% grey): EF, naso–premaxilla elastic fibres; DLPM, dorsal premaxilla–maxilla ligament; LIM, interopercular–mandibular ligament; LIS, interopercular–subopercular ligament; ILPM, inner premaxilla–maxillary ligament; LPM, palatine–maxillary ligament; LRDM, articular–dentary–maxillary ligament; VLPM, ventral premaxilla–maxilla ligament. Scale bars, 10 mm.