Restricted structural diversity in the angelfish feeding apparatus drawn from clear-stained and dissected specimens (Table 1).

A, Pomacanthus [Arusetta] semicirculatus; B, Chaetodontoplus duboulayi; C, Pygoplites diacanthus; D, Genicanthus melanospilos; E, Centropyge [Xiphypops] bispinosa; F, Centropyge [Centropyge] bicolor. Bone labelling in A (B–F follows): art, articular; d, dentary; ect, ectopterygoid; hyom, hyomandibular; ihy, interhyal; iop, interoperculum; mpt, metapterygoid; mx, maxilla; nc, neurocranium; op, operculum; pal, palatine; pmx, premaxilla; pop, preoperculum (in fine stippling); q, quadrate; sop, suboperculum; supcl, supracleitrum; sym, symplectic; lc, lachrymal; v, vomer. Shading denotes space not occupied by bone; ligaments are shown in black. Black shapes with white margin, as indicated with black arrowheads in C–F, are cartilaginous discs unique to the pygmy angelfish clade (Figure 2). Note the reduced suspensoria in Genicanthus (C) and C. [Xiphypops] (D). For clarity, drawings only include cranial structures, except in (B), where the positions of reflective markers glued to the skin of kinematics study animals are indicated: 1, tip of anterior-most lower jaw; 2, base of pectoral fin; 3, anterior-most upper jaw; 4, mandibular (ancestral) lower jaw joint; 5, posterior joint between cheek region and (suspensorium) and neurocranium; 6, reference point in front of eye; 7, base of first dorsal spine; 8, intramandibular (derived) lower jaw joint; 9, ligamentous link between bones of the gill cover. Scale bar, 5 mm.