Data from: Lower jaw modularity in the African Clawed Frog (Xenopus laevis) and Fire Salamander (Salamandra salamandra gigliolii)

Modularity describes the degree to which the components of complex
phenotypes vary semi-autonomously due to developmental, genetic, and
functional correlations. This is a key feature underlying the potential
for evolvability, as it can allow individual components to respond to
different selective pressures semi-independently. The vertebrate lower jaw
has become a model anatomical system for understanding modularity, but to
date, most of this work has focused on the mandible of mammals and other
amniotes. In contrast, modularity in the mandible of lissamphibians has
been less well-studied. Here, we used geometric morphometrics to quantify
the static (intraspecific) modularity patterns in
Xenopus laevis and Salamandra salamandra gigliolii. We tested developmental and functional hypotheses of modularity and demonstrate that both species exhibit significant modularity. Functional modularity was supported in Xenopus, yet the lack of definitive support for both the developmental and functional hypotheses in Salamandra suggests influences on modularity are much more complex. Allometry has a small yet significant impact on lower jaw shape in both taxa and sex has a significant effect on shape in Xenopus. The high modularity seen in both species mimics the results of other studies on the amphibian cranium, suggesting that modularity is a ubiquitous feature of the tetrapod jaw.