Figure 2.

Ideograms showing the relationship between attenuation and vertebral proportions for individuals of three species of plethodontid salamanders. Three specimens displaying different morphologies are shown. Each was radiographed to show the skeleton. (Left) Oedipina stenopodia from Guatemala. (Center) L. lineolus from México. (Right) P. leprosa from Mexico. The two elongate species have the same head + body length, and the major difference between them is that the vertebrae of Lineatriton are longer than those of Oedipina, which are about the same length as those of Pseudoeurycea, a shorter-bodied form with a head slightly larger than the other two individuals illustrated. Every fifth vertebra is shaded, to better display the effect of vertebral lengthening. Each species has a single cervical vertebra (the atlas) and a single sacral vertebra; there are 20 trunk vertebrae in Oedipina but only 14 in Lineatriton and Pseudoeurycea. The transverse processes of the sacral vertebra of Lineatriton are located in an extreme posterior position, and they are directed posteriorly, effectively adding to the relative interlimb distance as compared with the other species. The morphology displayed by Oedipina is a common homoplasy in plethodondontid salamanders, seen for example in the distantly related bolitoglossine genus Batrachoseps from California.