Skeletal Development and Adult Osteology of Bombina orientalis (Anura: Bombinatoridae)

Although the morphology of frogs in the archaeobatrachian genus Bombina has been the subject of several studies, the results of these are difficult to compare. Therefore, the skeletal developmental and adult osteology of these frogs remain poorly understood. We describe the skeletogenesis, chondrocranial development, and the adult skeleton of Bombina orientalis on the basis of cleared-and-stained and dry skeletal specimens. In B. orientalis, the first elements to ossify are the long bones of the hind limb (Stage 36). This is followed by the ossification of the frontoparietals, exoccipitals, parasphenoid, neural arches, ilium, dermal elements of the pectoral girdle, and long bones of the forearm (Stage 37). Metamorphic climax begins at about Stage 41 with major modifications of the chondrocranium. By Stage 46, most of the cranial and postcranial elements are ossified, with the exception of the carpals. Comparisons of the timing of initiation of skeletal ossification among several taxa suggest that this species exhibits variation in ossification sequence that may relate to precocious development of the hind limb or early onset of cranial and axial ossification.