Anatomical, morphometric and radiographic study of the humerus in lesser anteater (Tamandua mexicana Saussure, 1860): terminological and functional analyses

Tamandua is a neotropical mammal genus that belongs to the superorder Xenarthra . The thoracic limbs of Tamandua have anatomical adaptations that widely differ from other mammals, and there are frequently specimens in wildlife care centers with traumas in their limbs. However, there are few studies describing the radiographic and morphometric anatomy of the humerus in Tamandua , or describing partially the bone reliefs. Thus, the main objective of this study was to describe the characteristics of the humerus of Tamandua mexicana based on gross dissections, radiographies and measurements comparing with other studies in the three Vermilingua genera, and establishing more suitable terminology. Twelve thoracic limbs of six death specimens of Tamandua mexicana were analyzed. The bone reliefs, ligaments, muscles and neurovascular structures related to the humerus were identified, and the suitable terminology to the humerus of Tamandua was established. Morphometric measurements of each bone relief were taken, and the data were statistically analyzed with the Wilcoxon non-parametric test for functional proposes. The humerus of Tamandua has anatomical characteristics mainly to offer greater areas to the muscles that act on the shoulder flexion and hand movements. Even the articular reliefs are lesser than the adjacent non-articular reliefs, the muscles and ligaments are the anatomical structures that give more stabilization to the shoulder and elbow joints. The deltosupracondylar ligament can be partially ossified in older adult specimens, and neurovascular structures pass through the supracondylar foramen. These anatomical characteristics must be accounted for in the radiological diagnosis and surgical approaches.