Dolphins have a streamlined fusiform body which has been adapted by evolution to swim fast in the ocean. There is a diversity of sizes which range from 1.7 meters up to 8 meters in length, but they have characteristics that differentiate them from porpoises and other cetaceans.

Dolphins are an informal subset of the order Cetacea. Therefore they share some characteristics, but they also have some significant differences.

Most species have gray skin tones ranging from light to dark gray, but most have whitish bellies. There are some other with black, blue, brown colors with stripes, spots or even huge parts of their bodies. Some river dolphins have pinkish skin combined with different shades of gray or white.

The patterns of these colors in their bodies and the lines and stripes in their skins are also assorted.

Most dolphins have a fin at the top of their back which helps them to balance and direct their body and a horizontal caudal fin that moves from top to bottom that creates the movement. However, to add more variety to dolphin anatomy, not all dolphins have this dorsal fin as a couple of species lack of it. Notice that the caudal fin does not move from side to side as can be observed in fish.

Finally, all Dolphins have a pair of flippers that help to give direction to the movement when swimming.

Dolphins are mammals because they nourish their offspring with milk produced by the mother.

They are also vertebrate, warm blooded and breathe air through their lungs which are common characteristics of mammals.

Although they don’t have long hair like most mammals, some of them they still have tiny hair all over their skin.

There is a vast diversity of colors and patterns in the skins of the different dolphin species. While the most dolphins common species are gray, there are other species with black stripes, spots, scratches or bands. Even more, some species are pink.

Dolphins have a streamlined body which has several important and impressive adaptations to swim efficiently in the ocean.

Another important characteristic about the appearance of dolphins is their top fin, which is very representative of their anatomy, although there are a couple of finless species.

Dolphins breathe through a hole in the top of their head which is called blowhole.

The blowhole can empty and refill the lung in one-fifth of a second through an explosive blow which can reach velocities up to one hundred miles per hour.

The blowhole is closed tightly by a group of strong muscles surrounding it, which avoid water from getting in.

The air introduced through the blowhole, is conducted to the lungs for getting oxygen, which is a huge difference with fishes who use gills to breathe.

Dolphin weight varies from species to species. For the smallest dolphins, the weight can be 50 Kg and the largest species like the orca can weight up to 4 tons.

Bottlenose dolphins weigh between 150 y 650 kg.

Dolphins are cetaceans which are a group of mammals fully adapted to live in the water. While most species live in the oceans and seas, few species dwell in rivers.

However, dolphins are an informal group which is not self-contained taxonomically. They belong to the family Delphinidae which includes the oceanic dolphins, but this group also includes the river dolphins.

Like all mammals, they have warm blood and breathe through lungs. Dolphins are one of the most intelligent animals in the world that have excellent communication capabilities.