Comparaison de la structure et du volume squelettiques entre un delphinidé (Delphinus delphis L.) et un mammifère terrestre (Panthera leo L.)

The weight and structural characteristics of bones (density, ash content, and structural compactness) were compared between a small delphinid (Delphinus delphis L.) and a terrestrial mammal (Panthera leo L.). The aim of this comparison was to show the morphological correlates of the steep reduction in skeletal mass, which is a characteristic of dolphins. The lightness of the bones in the thoracic limbs of these animals is due to a reduction of both the volume and the density of bones. In the cephalic and thoracic regions, the loss in mass of the delphinid skeleton is due only to the reduction of bone volume. Dolphin vertebrae show no modification of weight or structure, as compared with those of lions. The functional hypotheses suggested by these results are discussed in relation to aspects of bone pathology induced by disuse or abnormal gravitational conditions.