Evolution of the jaw apparatus in pythons

摘要

Principal component analysis of 17 measurements of the jaw apparatus in seven species of pythons and Boa constrictor reveals that variation in these data was largely size-related (variation along PC1 = 95.0%) and species discrimination was limited due to confounding within- and among-species size effects. Discriminant function analysis of size-corrected data indicate that (1) these species are distinguishable on the basis of jaw apparatus morphology and (2) these differences broadly correspond with habitat preference (arboreal, semiarboreal, terrestrial). Arboreal/semiarboreal species have an elongate braincase that is widened anteriorly, and elongate quadrates and pterygoid bones, traits most pronounced in the most arboreal species, Morelia vividis. Terrestrial species, in contrast, have a widened premaxilla and elongate snout, maxillae, palatines, supratemporals, and mandibles, traits most pronounced in Python molurus and P. sebae. These differences appear to be functionally correlated, suggesting that the evolution of individual elements of the jaw apparatus have been constrained to maintain the functional integrity of the system. These differences are also highly congruent with current phylogenetic hypotheses of these python species.