PMC

Growth model plots for angular deviations of the jaws in P. motoro during prey-processing behaviour for three different prey types.

Computed tomography scans of (a) P. motoro teeth (the animal analysed in this study, an insect-feeding generalist predator) and (b) P. orbignyi (a sympatric, insect-feeding specialist). Jaws were protruded normally (as opposed to asymmetrically), flexing the mandibular symphyses. This action pinches the dental ligament, reorienting the teeth in some batoids []. (Online version in colour.)

Functional morphology of asymmetrical jaw protrusion in Potamotrygon motoro. (a) Resting jaw and hyomandibular articulations; (b) asymmetrical protrusion of jaws relative to kinetics of angular cartilage and hyomandibular articulations (inset and pointer: photo of asymmetrical protrusion of live Potamotrygon while feeding on insect larva); (c) medial flexion of mandibular (Meckelian) symphyses; (d) computed tomography scan of Potamotrygon motoro crania (inset: articulation of jaws to hyomandibular cartilage via dual angular cartilages). The number of angular cartilages varies in potamotrygonids, in P. motoro there are two angular cartilages (ii). These angular cartilages bridge the gap between the hyomandibulae (i) and the palatoquadrate (upper jaw; iii) and Meckel's cartilages (lower jaw; iv). (Online version in colour.)