The skeleton of the green Iguana iguana (Squamata: Iguanidae) and its intraspecific morphological variation.

The green iguana (Iguana iguana) is an iguanine lizard with herbivorous and arboreal habits, whose distribution spans through South America, Central America to the south of North America. Although the genus Iguana is well-known, the species still lacks a comprehensive and up-to-date anatomical study, particularly addressing the axial skeleton, including intraspecific variation. This study provides an anatomical revision of the species, providing a detailed redescription of its cranial skeleton and the first comprehensive analysis of its axial skeleton. Here we use X-ray computed tomography, 3D segmentation and osteological analyses to examine nine specimens. Significant individual variability was observed in the shape and proportions of skull bones, the presence and absence of a neural spine in the atlas vertebra, rib count and caudal vertebrae morphotypes. Notably, the nasal and frontal bones exhibited shape variation related with specimen size. The caudal vertebrae exhibited considerable variation across specimens, presenting seven distinct morphotypes with consistent sequence but individual variation in their quantity and presence. Moreover, the caudal vertebrae variability contrasts with the previously known caudal pattern for the species. These findings expand our understanding of the morphological diversity within I. iguana.