Morphological novelty in the limb skeleton accompanies miniaturization in salamanders

Science  30 Aug 1985:
Vol. 229, Issue 4716, pp. 871-874
DOI: 10.1126/science.4023715


Salamanders of the genus Thorius (Plethodontidae) are among the smallest tetrapods. Hypotheses of limb skeletal evolution in these vertebrates were evaluated on the basis of estimates of natural variation, comparisons of skeletal homology, and analysis of molecular phylogeny. Nine carpal arrangements occur in Thorius, more than in all twelve related genera of typically larger salamanders; six of these arrangements are unique. They represent a trend toward a decrease in the number of separate cartilages that is independent of locomotor and ecological specialization. Miniaturization may be an important source of morphological novelty, distinct from local adaptation, in vertebrates.