Morphometric analysis of adult Hippopotamus forelimb bones

Background: Understanding the adaptative changes in bone shapes among animals involves studying bone morphology. We examined adult hippopotamus (Hippopotamus amphibius)forelimb bones at the anatomy laboratory of Patuakhali Science and Technology University, Bangladesh. Samples were collected from Rangpur Recreation Park and Zoo between September 2021 and July 2022. Methods: Bones were processed by removing mud and boiled with water. Subsequently, hydrogen peroxide was used for one and a half hours to remove any remaining muscular tissues from the bones. Following this, the bones were air-dried under sunlight for a month. Measurements of key parameters including length, height, width, circumference, and weight were obtained using calibrated instruments, thereby ensuring precision. Results:The scapula displayed a pronounced and elongated spine – the spina scapulae – that demarcated the lateral surface into two distinct fossae: the supraspinous fossa and the infraspinous fossa. The distal expansion of the spine, known as the acromion process, consisted of the fused hamate process and suprahamate process. The head of humerus was round and featured two undivided tubercles: the greater or major and the lesser tubercle. On the medial surface, a small and shallow radial fossa was observed, while on the opposite side, a large and deep olecranon fossa was present. The proximal surface of the radius head exhibited concave fovea capitis radii, which articulated with the lateral condyle of the humerus. The shaft of the radius was slightly expanded in the cranio-caudal direction. Similarly, the shaft of the ulnahad a somewhat triangular shape, resembling the shape of the radius shaft. Medially, it had a convex facet that articulated with the radius, and cranially, the interosseous space between the radius and ulna was longer than the caudal view. Conclusions: The unique anatomical features and morphometric measurements of the forelimb bones in hippos can be beneficial for identification, radiographic interpretation, and forensic investigation. Furthermore, this study provides essential guidelines and insights for understanding appropriate anatomical parameters.