Figure 6.

Skull and jaw joint morphology in the psittaciform bird Ara ararauna (blue and yellow macaw; University of Chicago Research Collection, UCRC R1). (a) Skull in lateral view. (b) Disc-shaped left quadrate condyle in posteroventral view. (c) Trough-shaped socket in left lower jaw for quadrate condyle in dorsal view. Skull morphology highlighted: 1, small, elevated external nares; 2, short, deep snout; 3, coossified cranial vault; 4, pendant, elongate pterygoid flanges for enhanced pterygoideus musculature; 5, jaw joint allowing fore-aft movement; 6, short, deep dentary ramus fused at the symphysis. Scale bars, 5 cm in (a) for enlarged view, 2 cm in (b) and (c). Abbreviations: adm, attachment for the depressor mandibulae; aqco, articular surface for quadrate condyles; oc, occipital condyle; pt, pterygoid; qco, quadrate condyle; rap, retroarticular process.