Epomops franqueti: The mammalian bony thorax built for flight

Abstract

The vertebral column is an important component of the axial skeleton as well as the bony thorax and the appendicular skeleton as they provide support and stability, especially during flight. The bony thorax and vertebral column of avian species have been adequately investigated. However, few works on the osteology of bats relative to their ability to fly have been done. Therefore, to enrich the repertoire of knowledge of how bats osteology enhance and sustain their flight through long distance of several kilometers, the vertebral column and bony thorax of Epomops franqueti was investigated. Ten Epomops franqueti were captured from their roost using mist net. They were anaesthetized using ketamine HCl (Biotechnica Pharma Global (BPG), China) at 25mg/kg body weight intramuscularly on the medial side of the thigh muscle. They were sacrificed, eviscerated, de-fleshed and the bones were prepared using cold water maceration method. The vertebral column in Epomops franqueti presented a cylindrical outlook that was wider at the cervical region but tapers at the lumbar region. The post cranial skeleton in the Epomops franqueti had seven cervical skeletons, twelve-thirteen thoracic vertebrae, three-four lumbar vertebrae, the sacral vertebrae were fused, numbered between two and three. The atlas in the Epomops franqueti was relatively larger than the other cervical vertebrae. The thoracic vertebra lacked mammalian characteristic spinous process. The inconspicuous transverse process was dorso-laterally located on the thoracic body, with a vertical orientation. It possessed a small cranial spine like process that articulated caudally with the preceding vertebra. The rib had two components: The vertebral and sternal ribs. The vertebral rib was oriented caudo-ventrally with the thoracic vertebrae. The head of the rib articulated with the costal facets, cranially and caudally, between two adjacent thoracic vertebrae. The tubercle of the rib articulated with the transverse costal facets, dorso-laterally. The sternal rib had ossified costal cartilage similar to the reports on the avian species. The sternebrae were fused with a bilaterally 
flattened process that projected ventrally like the keel in the avian species. The lumbar vertebra lacked the characteristic mammalian plate-like transverse process. The lumbar was fused with the sacrum which continued with the small coccygeal bones. Although the atypical mammalian vertebral column did not share tremendous similarities with that of avian vertebral column, the bony thorax in the Epomops franqueti had some similarities with that of the avian species. They vertebral column and bony thorax in the Epomops franqueti provided structural platform for flight muscles, and support and stability during flight.