General Information
The dolphin is a typical representative of the mammals of the cetacean class, which, despite living underwater, do not have gills for underwater breathing. In fact, the aquatic lifestyle has influenced the body shape of these mammals: dolphins have a dorsal fin and a streamlined long body shape. In addition, dolphins have no external ears, and the role of “hearing” is performed by a strongly developed inner ear, which allows the mammal to use echolocation.
The range of animals is wide: dolphins can live in any body of water and quickly adapt to the salinity and temperature of the water. Fish, plankton, and small crustaceans, migrating in flocks, make up the central part of the diet of these mammals. The study of the social behavior of dolphins remains a big question: it is believed that whales have a developed intellect and are able to make weighted decisions, almost like a man (Hill et al. 1). In addition, dolphins often play with swimmers, which indicates the cognitive thinking capabilities of these mammals.
Skull structure
The structure of the skull of dolphins is well studied: the underwater lifestyle should be taken into account in the study. The skull of dolphins contains all those bony formations which are characteristic of the skulls of most mammals. A considerable length of the skull consists of a dolphin’s beak, which is formed by the extension of the bones of the nasolabial zone. Along with the entire elongated dolphin, the visor has tiny teeth, and closer to the outer part of the jaw, teeth are minor. In dolphins, clearly distinguished are all areas of the skull, with the frontal area being more developed, which contributes to the increased massiveness of the skull. The cerebellum almost entirely overlaps with the front of the brain but performs all the same functions as in other cetaceans and mammals in general. The nasal foramen is shifted backward.
Structure of the postcranial skeleton
It is noteworthy that the dolphin, as a representative of mammals, is not a true tetrapod because, as a result of evolution, hind limbs have been reduced for the unnecessary. At the same time, the forelimbs eventually turned into wedge-shaped flippers, which allow steering of the body’s movement underwater. Each of the flippers consists of five rudimentary fingers of different lengths. In addition, dolphins have evolved a locomotor organ of the caudal fin that also allows them to balance during movement. The dorsal fin is composed of fibrous tissue and has no bones, and its purpose is to provide additional body thermoregulation. The dolphins’ spine is elongated, but the cross-section is reduced, which was a necessary sacrifice to allow the free body movement characteristic of underwater life.
Works Cited
Hill, Heather M., et al. “More Than a Fluke: Lessons Learned from a Failure to Replicate the False Belief Task in Dolphins.” International Journal of Comparative Psychology, vol. 31, 2018, pp. 2-23.