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Dolphins (Delphinidae), commonly known as ocean dolphins (unlike the river River dolphin or dolphins) are a family of toothed whales quite heterogeneous, which houses some 34 species.

They arebetween 2 and 9 meters long, fusiform body and large head, elongated snout and a single blowhole on top of the head (respiratory openings that many marine animals have as air or water contact with therespiratory system internally). They are carnivores.

Live relatively close to shore and often interact with humans. Like other whales, dolphins use sound, dance and jump to communicate, navigate andreach their prey, they also have a sixth sense of echolocation, emitting sounds in their environment and interpret the echoes generated by the objects around them.

Evolution [edit] It has longbeen thought that dolphins, along with the rest of cetaceans, were descendants of terrestrial mammals, the mesoniquios, extinct order of carnivorous ungulates. However, it has been shown that in fact thewhales (including dolphins) are closely related to artiodactyls, especially with the hippos. [1] It is estimated that during the Eocene (about fifty million years ago), ancestors of cetaceans tookrefuge in the water, similar to tragúlide [2].

Fossil evidence shows that appeared in the Miocene odontocetes. The first known dolphins belong to the genera and Hadrodelphis Kentriodon,Ketriodontidae family. These primitive dolphins had a developed sense of echolocation and melon body skeletons of modern dolphins have two small bones in the sacral spinal cord, which corresponds to remnants ofthe pelvis. In the ancestors of dolphins, which had been investigated and four legs and has been evolving

Los delfínidos (Delphinidae), llamados normalmente delfines oceánicos (a diferencia de losplatanistoideos o delfines de río) son una familia de cetáceos odontocetos bastante heterogénea, que alberga unas 34 especies.
Miden entre 2 y 9 metros de largo, con el cuerpo fusiforme y la cabeza...