FIGURE 7.

Typical morphological variants of lumbosacral and sacrococcygeal transitions in isolated sacra. Entire spine (left panels), isolated sacrum in ventral view (mid panels), and dorsal view (right panels). (a). Complete lumbarization with detachment of the first sacral element (S1; Castellvi Type IA) and partial sacralization of the coccyx. (b). Partial lumbarization of S1 with complete coccyx sacralization (Castellvi Type IV). (c) Partial sacralization of L5 (Castellvi Type IIIA). (d) Complete sacralization of L5 (Castellvi Type IIB). (e, f) Different stages of incomplete lumbarizations, which were always paired with coccyx sacralizations (Castellvi Type IIIB). Note that we did not find a morphologically corresponding case of lumbar sacralization. (g, h) Sacra without morphological evidence for a lumbosacral transitional vertebra, classified as numeric (meristic) aberrations. (g) Sacrum with four sacral elements and coccyx sacralization. (h) Sacrum with six sacral vertebrae and no indication of coccyx sacralization