The development of the Chondrocranium in two species of the Australian anuran genus Pseudophryne Fitzinger

Abstract

A comparative study has been made of several stages in the chondrocranial development of two species of the Australian anuran genus, Pseudophryne. The material has been studied by microscopic examination and graphic reconstruction of serial transverse sections. In tadpoles of stage 20 (small limb bud) the chondrocranium is very rudimentary, consisting of little more than an open box with a membranous roof. In later development it becomes somewhat more solid but lacks many elements present in most genera, especially in the nasal and orbital regions. It never has a well-developed roof. However, the genus retains a heavy, primitive quadrate. The various processes interconnecting the chondrocranium and the jaw complex are unusual in position and size as a result of the problem of forming a functional unit from the specialized chondrocranium and the primitive quadrate. The evolutionary position of the genus is discussed in the light of these characters compared to other known genera both primitive and specialized. It seems that Pseudophryne, although retaining some primitive characters, is highly specialized.