Adaptation and Evolution in the Hand Muscles of Australo-Papuan Hylid Frogs (Anura: Hylidae: Pelodryadinae)

Abstract

Members of the Pelodryadinae possess a hitherto undescribed set of distal extensor muscles to the ultimate phalanges; this set is found also in the hyline frogs that formed an outgroup for this study, and also in scansorial but not terrestrial microhylids. The M. palmaris longus of Cyclorana consists of two slips, whereas in most other pelodryadines the division is three-fold. The problematic species Litoria alboguttata and L. dahlii exhibit the Cyclorana condition. The hand musculature of Litoria infrafrenata is typical of its genus, and this study gives no support to the hypothesis that this species has evolved independently of the other pelodryadines; however, there is support for the hypothesis that montane New Guinean Litoria are closely related to some members of the freycineti assemblage of mostly terrestrial frogs. The hand musculature of Nyctimystes possesses no features to distinguish it from that of a generalised Litoria species, and sheds no light on the origins of Nyctimystes.