Morphology

Lizards and snakes form a monophyletic group called squamates. Among them, a large number of species have their limbs reduced or absent. On a seemingly unrelated note, the squamates’ head features a structure called chondrocranium: a structural frame made of cartilage - it supplements the skull made of bone. The chondrocranium is also found to be reduced in several species across squamates. It turns out that reductions in limbs and chondrocranium are, for some reason, correlated.

Paper

Limb reduction in squamate reptiles correlates with the reduction of the chondrocranium: a case study on serpentiform anguids. Yaryhin, O., Klembara, J., Pichugin, Y., Kaucka, M., and Werneburg, I. Developmental Dynamics, 2021. (link)