Heterochronous Changes Among Australian Leptodactylid Frogs

This investigation has been carried out in order to estimate the extent to which osteological differences normally used as a basis for generic distinction among certain anurans may be explained on the basis of heterochronous changes in bone formation. Representative species of fourteen Australian genera of the family Leptodactylidae were compared, and an osteological survey was carried out on alizarin transparencies of sexually mature and juvenile specimens. As a basis for description, a little known and somewhat neotenic Western Australian anuran, Glauertia russelli Loveridge, was selected. Bone, as a tissue, is a useful index of heterochronous change. It gives a clear indication of the extent to which the developmental processes leading to its formation have proceeded. It often provides a reliable guide to the degree of general development attained by the time an animal reaches sexual maturity. The study of heterochrony indicates the evolutionary importance of this phenomenon in the establishment of certain species and genera. Skeletal distinctions among the Australian Leptodactylidae are readily explained, even at the generic level, in terms of such time‐axis or heterochronous changes. These, through shortening or lengthening the time of development of particular bones, or by altering the speed of their ossification, lead to differences of phylogenetic significance. The fact that not only individual variations but also specific and generic distinctions may arise in this way in certain groups of animals has an important bearing on problems of their distribution.