This study examines morphological features of the postcranial skeleton in a sample of modern anurans of known locomotor style within the context of a recent phylogenetic hypothesis. Non-destructive methods for collecting skeletal morphometric data from alcohol preserved anuran specimens are herein proposed and tested. Analysis of covariance (ANCOVA) is used to compare morphological structures taking into account differences in body size (SVL) among taxa.
Results of this study differ from previous studies in that the patterns of morphological correlates in anurans may not span the entire anuran clade, but are identifiable within phylogenetically focused comparisons. Manus size was predicted to be larger in arboreal than non arboreal anurans, a pattern supported by comparisons within the family Hylidae, and in the derived group Natatanura. Arboreal bufonid species exhibit wider sacra and longer fore- and hind limbs relative to SVL than do terrestrial species. natatanurans capable of long distance jumping exhibit a larger pes (wider and longer) relative to SVL than do arboreal species. Sacral diapophyseal angle (SDA) provides a method of separating walking/running species from all other locomotor groups examined with the exception of members of the strictly aquatic family Pipidae.
Fossil anuran specimens recently discovered in Oligocene deposits in the Rukwa Rift Basin of Tanzania preserve pelvic anatomy associated with forceful jumping in modern forms. An estimated sacral diapophyseal angle (SDA) for RRBP 04101 of 21.409° is consistent with this locomotor assessment.