EVOLUTIONARY TRENDS IN FROGS

Fossil evidence concerning the Anura adds guide-lines to phylogeneticinterpretations, but in large part evolutionary informationhas come from comparative studies of moderns. Trends withinthe Anura, established in different lines, provide an importantsource of clues for major phylogenetic interpretations. A numberof such trends, both osteological and non-skeletal, are analyzedand their phylogenetic implications assessed. Two major lines of development are postulated. One branch includesthe notobatrachid-ascaphid and the pipid-rhinophynid sublines.The other major branch includes the advanced frogs with procoelouscentra. The advanced frogs were derived from a primitive stockprior to the development of anything that would be recognizedas a notobatrachid-ascaphid-opisthocoelan line, rather thanfrom such a line.