THE HEAD SKELETON OF GLYPTOSTERNUM RETICULATUM McCLELLAND & GRIFFITH

Abstract

SUMMARY The genus Glyptosternum is diagnosed osteologically. In the arrangement and topography of bones, the skull shows resemblance to the Siluroid configuration. Reduction in the number of bones is a feature of the catfishes and is farthest reached in G. reticulatum, which tends to lose interhyals, entopterygoids, supratemporals and second hypohyal on each ramus of hyoid arch. The vomer and ectopterygoid are without teeth and the hyomandibula is suspended solely from the sphenotic. Of the two prominent fontanels, the posterior frontoccipital fontanel is confined between the frontals and supraoccipital. An additional bone associated with the orbit is reported in this catfish. The circumorbital ring is divided into many tiny pieces. The posttemporal is unforked, lacks the inferior limb and is suturally united with the posterolateral flank of the skull. The occipital process is quite feeble and the posterior part of the skull is not deeply excavated. Support is cited for splitting up of the composite genus...