A Tale of Appendages: Investigating Limb and Tail Variation in Salamanders

The evolution of limbs and tails in tetrapods has been widely studied as key traits for locomotion, balance, and evolutionary biology, but only under a "life-history" perspective, which may not explain all the morphological differences observed within this group. In this context, leveraging a dataset covering 44% of salamander species, we compared appendage proportions across families, ecological groups, and sexes within a phylogenetic framework. Plethodontidae showed shorter limbs compared to other families, while aquatic species had the opposite trend. Basal families had the shortest tails, while terrestrial species had the widest ones. Furthermore, some families showed divergence in limb proportions: Ambystomatidae had shorter forelimbs than hindlimbs, while Salamandridae had longer forelimbs than hindlimbs. Phylogeny explained most variation, but ecological adaptation and convergence also played roles. Our study confirms that animal body form is probably driven by a combination of evolutionary history and ecological drivers. We think that expanding this multi-disciplinary phylogenetic perspective to other elements of interest, such as caudal vertebral number and foot shape, may help to better understand the evolution and adaptation of appendages in Caudata.