Clavicle in Carnivorans: A Forgotten Bone.

The clavicle is a bone whose development is related to the versatility of the thoracic limbs in mammals. Studies with vestigial structures are scarce and controversial, especially in the order Carnivora. The objective of this study was to verify the presence and to investigate the shape and constitution of the clavicle in neotropical carnivores. In order to do this, 108 cadavers of 19 different species were collected dead on highways and were analyzed. The clavicles were submitted to dissections, longitudinal length measurements, radiographs, histological sections and, in some cases, diaphanization. Sixteen of the 19 species had clavicles in both sides, being significantly larger (P < 0.05) and distinctly more radiopaque in the felids than in the other families. There were no macro or microscopic evidence of clavicle in the specimens of Nasua nasua (n = 6), Conepatus semistriatus (n = 2), and Conepatus chinga (n = 1). The clavicle of the males of Lycalopex gymnocercus, Galictis cuja, and Leopardus geoffroyi was significantly larger (P < 0.05). The predominating contour of the clavicles was a thin stick with cranial convexity. The histological sections demonstrated compact bone consisting of trabecula and lamellae filled by bone marrow and different levels of occupation by chondroid matrix. It can be proposed the clavicles of the order Carnivora, although vestigial and rarely absent, have their presence, constitution and shape more associated with the phylogenetic proximity and evolutionary history of the species than to the variety of movements the thoracic limbs perform in free-living conditions. Anat Rec, 2019. © 2019 American Association for Anatomy Anat Rec, 303:1831-1841, 2020. © 2019 American Association for Anatomy.