overlaps overlaps vertebra plane of autotomy fracture plane vertebral fracture plane plane of autotomy bisecting vertebral bone Interestingly, zones of cartilage or connective tissue do not demarcate the fracture planes in A. carolinensis, as seen in other lizard taxa (Cox, 1969a; Hoffstetter and Gasc, 1969)[PMID:22753107] Many authors (e.g., Holder, 1960; Mufti and Hafiz, 1972; Bellairs and Bryant, 1985; Russell and Bauer, 1992) have referred to the more proximal caudal vertebrae that lack fracture planes as 'pygal vertebrae' and the more distal caudal vertebrae that possess fracture planes as 'postpygal vertebrae' However, many lizard taxa lack fracture planes in their caudal vertebrae altogether, making this classification difficult to apply in these cases (Etheridge, 1967; Bellairs and Bryant, 1985). Furthermore, in some species (including A. carolinensis) the most distal of the transverse process-bearing vertebrae may possess fracture planes and should technically be called postpygal vertebrae, despite the fact that they more closely resemble the more proximal, non-fracture plane-bearing vertebrae in overall morphology (Cox, 1969a)[PMID:22753107] UBERON:0035088 A plane of autotomy that divides an appendage through a vertebral bone.