Fig. 1. Schematic dorso-ventral representation of the tongue of Python molurus and its extrinsic muscles. (A) Abbreviations: cbr, ceratobranchial; m, mandible; dsh, distal tongue ensheathing; ggl, m. genioglossus; hgl, m. hyoglossus; psh, proximal tongue ensheathing; sh, tongue sheet. The dental bone forms the local coordinate system of the head. Although the head is highly deformable during feeding, the lower jaws do not deform during tongue flicking. The position of the ceratobranchials is assumed to be fixed to the skull during tongue flicking (e.g. Bels et al., 1994). The mm. genioglossi and the mm. hyoglossi are able to protract and retract the tongue relative to the mandibles and ceratobranchials. Proximally on the tongue, the mm. hyoglossi are ensheathed. This tubular tongue sheet encloses the tongue distally up to the tongue tips, inverts into itself and connects to the tongue at the distal tongue ensheathing (McDowell, 1972). The outer tongue sheet is connected to the muscles and connective tissue of the mouth floor. The inverted inner part is protruded while the tongue elongates. (B) Radio-opaque marker positions at rest: 1–5, local coordinate system fixed (glued) to the jaws (skin); 6, fold of the tongue sheet at maximum tongue retraction – the outer layer of the tongue sheet is fixed to the connective tissue of the mouth floor; 7, point of bifurcation (marker injected); 8, proximal tongue ensheathing (marker glued after manual protrusion of the tongue); 9, 10, tongue base (markers injected). (C) Hypothetical displacements of the markers indicating the relative translation and elongation of the soft tissues.