Functional relationships in the jaw apparatus of the chameleons and the evolution of adaptive complexes

Abstract

The distinctive features of the jaw apparatus in chameleons (hyperstreptostyly, amphikinetism reduction, transformation of the cranial roof into a “casque,” the jugo-mandibular ligament, the shape and position of quadrate bones, and the structure of jaw adductors) emerged as adaptations for the refinement of the mechanism of prey capture by the tongue. The development of another group of features (loss of the epipterygoid, m. levator pterygoidei, and structures associated with the middle ear) was an indirect consequence of the adaptations listed above. The formation of a specialized mechanism for prey capture by the tongue played a role of a key innovation (macromorphosis) in the phylogeny of chameleons. The ontogenetic relationships between the aforementioned features of the jaw apparatus of the chameleons are adaptive correlations, and the evolutionary transformations of these correlations correspond to biological coordinations. The evolutionary mechanisms underlying the formation of correlation and coordination interrelations in the organism are considered.