Wing and tail myology of Tyto furcata (Aves, Tytonidae).

Barn Owls (Tytonidae) are nocturnal raptors with the largest geographical distribution among Strigiformes. Several osteological, morphometrical, and biomechanical studies of this species were performed by previous authors. Nevertheless, the myology of forelimb and tail of the Barn Owls is virtually unknown. This study is the first detailed myological study performed on the wing and tail of the American Barn Owl (Tyto furcata). A total of 11 specimens were dissected and their morphology and muscle masses were described. Although T. furcata has the wing and tail myological pattern present in other species of Strigiformes, some peculiarities were observed including a difference in the attachment of m. pectoralis propatagialis due to the lack of the os prominence, and the presence of an osseous arch in the radius that seems to widen the anchorage area of the mm. pronator profundus, extensor longus alulae, and extensor longus digiti majoris. Furthermore, the m. biceps brachii has an unusual extra belly that flexes the forearm. The interosseous muscles have a small size and lacks ossified tendons. This feature may be indicative of a lower specialization in the elevation and flexion of the digiti majoris. Forelimb and tail muscle mass account for 10.66 and 0.24% of the total body mass, respectively. Forelimb muscle mass value is similar to the nocturnal (Strigiformes) and diurnal (Falconidae and Accipitridae) raptors, while the tail value is lower than in the diurnal raptors (Falconidae and Accipitridae). The myological differences with other birds of prey are here interpreted in association with their "parachuting" hunting style. This work complements our knowledge of the axial musculature of the American Barn owls, and provides important information for future studies related to functional morphology and ecomorphology.