Osteology and skeletal development of Phyllomedusa vaillanti (Anura: Hylidae: Phyllomedusinae) and a comparison of this arboreal species with a terrestrial member of the genus.

Few descriptions of skeletal development and morphology exist for neobatrachians, despite their abundance and diversity. Herein, the adult morphologies of Phyllomedusa vaillanti and P. atelopoides are described and compared and the ontogeny of the larval skeleton of P. vaillanti is described and compared with those of Hyla lanciformis (the only hylid for which a detailed cranial and postcranial osteological ontogenesis has been described) and P. trinitatis (the only other member of this genus for which the larval skeleton has been described). These descriptions and comparisons are made on the basis of cleared and double-stained, dry skeletal, and alcohol-preserved specimens. In P. vaillanti, the first elements that ossify are the neural arches of the presacral vertebrae (Gosner Stage 34), followed by the parasphenoid, occipital condyles, exoccipitals, and prootics at Stage 38; many elements of the postcranial skeleton ossify contemporaneously with the first cranial elements. Major modifications of the chondrocranium begin at Stage 44. In adults, the skulls of P. vaillanti and P. atelopoides do not seem atypical of hylid frogs, and their elements are gracile and unornamented. Although P. atelopoides is a terrestrial species, the morphology of its hands and feet does not seem to differ dramatically from that of other phyllomedusines, which are arboreal; however, the relative lengths of the appendages and vertebral column are shorter and more robust than those of all other Phyllomedusa.