Tail growth in Chamaeleo dilepis (Sauria: Chamaeleonidae): functional implications of segmental patterns

Patterns of growth of caudal vertebrae in the chameleon Chamaeleo dilepis were determined using principal component analysis, and compared to growth of the entire tail relative to snout-vent length. Despite significant positive allometry of the whole tail, growth rates of vertebrae differed along the length of the tail. Specifically, there was a proximal region that grew positively allometrically, and an extensive distal portion that grew with negative allometry. Intervening, was a short transitional region of approximate isometry. Positive allometry of the entire tail resulted from the extensive proximal region that grew in this manner. Although the region of positive allometry extended further caudad than the in. caudofemoralis longus, in. retractor penis magnus, and in. ischiocaudalis, its extent correlated more closely with the presence of neural spines (which are used as a proxy for the extent of the m. transversospinalis) and with tail coiling in this species. The positively allometric region housed the non-segmental musculature of the tail and did not bend, and the negatively allometric region identified the portion of the tail that was prehensile.