Estudio biomecánico y morfofuncional del esqueleto apendicular de Homalodotherium Flower 1873 (Mammalia, Notoungulata)

Abstract

Abstract. BIOMECHANICAL AND MORPHOFUNCTIONAL STUDY OF THE APPENDICULAR SKELETON OF HOMALODOTHERIUM FLOWER 1873 (MAMMALIA, NOTOUNGULATA). Homalodotherium (Santacrucian- Friasian; early Miocene) is the best represented genus of the Family Homalodotheriidae (Notoungulata). It was proposed as a digging form, browser on trees in food habits, and with potential for adopting bipedal posture. The appendicular skeleton is studied morphometrical and biomechanically, considering proportions, principal bone accidents, and muscular insertions, comparing with extant mammals. Bone elements of the appendicular skeleton are described, the musculature reconstructed, and 10 morphometric measurements used for calculating eight functional indices. Indices include deltoid proportion and epicondilar development of the humerus, ulnar robustness and olecranon proportion, femoral and tibial robustness, and distal extension of the fore and hind limbs. The forelimb preponderates force development in humeral flexion and protraction of the limb, but it can develop speed movements in the distal portion of the limb. The hindlimb lies upon the lateral side of the autopodium, and has an important development of force for body support and ankle stabilization (flexion and adduction of the femur, limb flexion, extension of the pelvic girdle, zeugopodium flexion, and extension, inversion and reversion of the autopodium). Homalodotherium would be able of adopting a bipedal posture. An arboreal browser habit is supported, but digging habit is discarded. Possibility of speed flexion of the zeugopodium could indicate a use of the forelimb for defence.