Wilga, C.D. A functional analysis of jaw suspension in elasmobranchs (2002) Biological Journal of the Linnean Society. 75: 483-502.

The morphology of the jaw suspension and upper jaw are quantified and related to upper jaw protrusion in five elasmobranchs possessing four jaw suspension types: broadnose sevengill, Notorynchus cepedianus, orbitostylic - amphistylic; spiny dogfish, Squalus acanthias, orbitostylic; bonnethead, Sphyrna tiburo, and lemon, Negaprion brevirostris, hyostylic; and Atlantic guitarfish, Rhinobatos lentiginosus, euhyostylic. The results indicate that jaw suspension type is not a good predictor of jaw mobility as previously thought. Instead, the best morphological predictor of jaw mobility appears to be either a long ethmopalatine ligament or no ligament, both of which allow the upper jaw to project further from the cranium. The morphology of the palatoquadrate-cranial articulation is key in determining the mobility of the jaws indicating that it should be included in descriptions of jaw suspension states. One advantage of upper jaw protrusion appears to be a reduction in the time to jaw closure by closing the mouth dorsally by upper jaw protrusion as well as ventrally by lower jaw elevation. A table of revised jaw suspension types is presented to illustrate the phylogenetic differences among gnathostome groups. Jaw suspension types mapped onto a gnathostome phylogeny support the evolution of holostyly and hyostyly from an autodiastylic ancestral condition.