Morphology of the cranial system of Platyclarias machadoi: interdependencies of skull flattening and suspensorial structure in Clariidae

Abstract

The African catfish Platyclarias machadoi stands out from other clariid species by its extremely dorsoventrally flattened skull. This paper focuses on the spatial constraints and consequent functional interde- pendencies in this very low skull (average skull height of 27.5±3.0% skull length); such as the medial position of the retroarticular process on the lower jaw, the hori- zontal position of the suspensorium, the lateral tilting of the pterygoid bones and the anterior part of the quad- rate with regard to the suspensorial transverse long axis. These characteristics can be presumed to have major influences on the capacity of suspensorial adduction, influencing the feeding and respiratory mechanisms. A comparison with other clariid species showed that one of the apomorphies is the presence of an extra muscle (musculus adductor mandibulae A3¢¢ pars levator tend- inis) in the adductor mandibulae complex. This extra muscle lifts the tendon complex of the adductor man- dibulae, resulting in a higher moment on the lower jaw. Some comments on the original species/genus descrip- tions are given.