Unravelling drivers on the morphological diversification of the terminal phalanx in hyloid frogs.

This article investigates the morphological variation of the terminal phalanges (specifically the fourth digit) in Hyloidea frogs to determine the influence of phylogenetic history, ecological microhabitats, locomotor abilities, and life-cycle constraints on their shape, evolutionary rates, and disparity. Analyzing 424 specimens from 128 species across 17 hyloid families, the study finds a complex pattern where phylogeny exerts a low but significant effect, and certain morphological traits—such as rounded proximal epiphyses and claw-shaped phalanges—converge in arboreal species, suggesting adaptations to climbing niches. Although microhabitat and locomotor categories show some shape differences and disparities, evolutionary rates do not significantly differ among groups, and life-cycle complexity (larval versus adult microhabitat) does not appear to constrain phalangeal morphology. Overall, the findings indicate that terminal phalanx shape in hyloid frogs reflects a multifactorial interplay of evolutionary and ecological factors rather than a single dominant constraint.