Abstract
Rhacophoridae, a family of morphologically cryptic frogs, with many genetically distinct evolutionary lineages, is understudied with respect to skeletal morphology, life history traits and skeletal ontogeny. Here we analyze two species each from two sister lineages, Taruga and Polypedates, and compare their postembryonic skeletal ontogeny, larval chondrocrania and adult osteology in the context of a well-resolved phylogeny. We further compare these ontogenetic traits with the direct-developing Pseudophilautus silus. For each species, we differentially stained a nearly complete developmental series of tadpoles from early postembryonic stages through metamorphosis to determine the intraspecific and interspecific differences of cranial and postcranial bones. Chondrocrania of the four species differ in 1) size; 2) presence/absence of anterolateral and posterior process; and 3) shape of the suprarostral cartilages. Interspecific variation of ossification sequences is limited during early stages, but conspicuous during later development. Early cranial ossification is typical of other anuran larvae, where the frontoparietal, exoccipital and parasphenoid ossify first. The ossification sequences of the cranial bones vary considerably within the four species. Both species of Taruga show a faster cranial ossification rate than Polypedates. Seven cranial bones form when larvae near metamorphic climax. Ossification of all 18 cranial bones is initiated by larval Gosner stage 46 in T. eques. However, some cranial bone formation is not initiated until after metamorphosis in the other three species. Postcranial sequence does not vary significantly. The comparison of adult osteology highlights two characters, which have not been previously recorded: presence/absence of the parieto-squamosal plates and bifurcated base of the omosternum. This study will provide a starting point for comparative analyses of rhacophorid skeletal ontogeny and facilitate the study of the evolution of ontogenetic repatterning associated with the life history variation in the family.
Highlights
Rhacophoridae (Old World tree frogs), are a monophyletic family [1,2,3,4,5,6,7,8] with a high diversity, constituting ca. 6% of the world’s anuran species [9]
Using an almost complete series of differentially stained tadpoles, metamorphs and adults, we examine the postembryonic skeletal development and adult skeletal osteology of the four species belonging to the two sister lineages of foam nesters: Taruga (T. eques and T. longinasus) and Polypedates (P. cruciger and P. maculatus)
The neurocranium is widest at the midpoint of the arcus subocularis in Taruga eques and T. longinasus but at the posterior end of the arcus subocularis in Polypedates cruciger and P. maculatus (Fig 2)
Summary
Rhacophoridae (Old World tree frogs), are a monophyletic family [1,2,3,4,5,6,7,8] with a high diversity, constituting ca. 6% of the world’s anuran species [9]. Rhacophoridae has been subjected to considerable recent taxonomic revisions, resulting in the recognition of many new independent evolutionary lineages at genus level [5,6,11,12,13,14,15,16]; 11 of the 18 recognized rhacophorid genera are recent descriptions. These new generic descriptions are largely based on molecular data and to a lesser extent on molecular data and morphology [13,14,16]. In recent phylogenetic reconstructions of rhacophorid relationships, adult skeletal data have been sparsely used [13,14], but never skeletal ontogeny
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