BERGMANN, P.J.*; RUSSELL, A.P.; University of Calgary, Calgary; University of Calgary, Calgary: Growth of the original tail in iguanian lizards: Are segmental patterns of growth conserved?

The original tail of lizards is composed of discrete, serially repeating vertebrae. Segmental (vertebral) patterns of tail growth were modeled using principal component analysis and compared to geometric mean regression slopes for the whole tail. Despite different allometric patterns of entire tail growth between species, segmental growth followed a conserved pattern in four species of iguanian lizard with highly divergent caudal functions. Specifically, segmental growth patterns were very similar for the arboreal, quadrupedal Anolis grahami and the terrestrial, semi-bipedal Callisaurus draconoides, which both have autotomic tails; as well as for the prehensile tailed Chamaeleo dilepis and extremely long tailed Calotes versicolor, which have non-autotomic tails. Patterns of tail growth are characterized by proximal vertebrae exhibiting positive allometry, and distal vertebrae growing in a negatively allometric fashion. A middle transitional region approximating isometry is also evident, but differs in extent between species. This pattern was mirrored by the scleroglossan gecko Pachydactylus turneri, which represents the sister group of the iguanians and further attests to the generality of the pattern observed. However, the pattern breaks down in Phrynosoma coronatum, an iguanian with a highly reduced tail. In this species the proximal portion of the tail shows negative allometry, while the distal portion grows positively allometrically. From the six species examined, it appears as though the pattern of segmental caudal growth is generally conserved in lizards, but may be modified in association with tail reduction.