SOME PHARYNGEAL JAW MUSCLES OF CALOTOMUS JAPONICUS (SCARIDAE, PISCES)

Abstract

The pharyngeal jaw muscles of Calotomus japonicus were examined. The structure of the infra pharyngeal crusher is similar to that of cichlids and labrids. That is, the fourth levator externus inserts on the lower pharyngeal bone, and the levator posterior is composed of two heads, one inserting on the fourth epibranchial and the other on the lower pharyngeal bone. The origin of the fourth levator externus is very specialized, being from a deep concavity on the neurocranium. It is conceivable that this specialization is correlated with the change of functional pattern of the pharyngeal jaw apparatus, and increases the relative importance of the fourth levator externus acting on the lower pharyngeal bone. The influence of this specialization on the shape of tbe brain, especially of the cerebellum, is discussed.