FIGURE 6.

Morphological features in sacra with transitional vertebrae. (a) Typical morphology of the cranial most sacral element in frontal view, whose supra‐adjacent segment shows complete lumbarization. Note that this segmentation anomaly leads to smooth and elongated sacral alae without apparent indentation between the prominent tip of the transverse (yellow) and the costal process, while the sacral base (red) is set deep between the sacral alae. Extra joint facets (nearthroses) on the alae articulating with the costal process of the supra‐adjacent vertebra might be present. (b–d) Sacrum with partial lumbarization of S1. (b) Cranial view showing dorsal displacement of the first sacral costal process (blue) with respect to S2. (c) Frontal view showing the highly positioned sacral base with respect to the sacral alae and a well‐developed transverse process (yellow) that is set apart from the costal process (marked blue in b). (d) Dorsal view of the incomplete fusion of the first segment of the median crest