Three-Dimensional Reconstruction of the Xenarthrous Process of the Thoracic and Lumber Vertebrae in the Giant Anteater

Abstract

The presacral vertebra of anteaters was examined by three-dimensional CT image analysis of the xenarthrous processes peculiar to the Order Xenarthra. The anteater is equipped with two following articulations in addition to the normal zygapophysial articulation. The dorsal xenarthrous process of the former vertebra articulates to the ventral area of the base of the mammillary process in the later vertebra. The pocket-like structure in the ventral area of the mammillary process receives the dorsal and ventral xenarthrous processes of the former vertebra. The complicated articulations do not obstruct the ability of the giant anteater to flex dorsally and laterally, however aids flexibility and strengthens the caudal thoracic and lumber regions of the animal. The xenarthrous processes and articulations may function as a supporter of the body weight during the bipedal standing posture when the anteater destroys the nests of ants and termites and protects itself from the enemies.