Delphinids include such well known dolphins as bottlenose dolphins and common dolphins as well as killer whales and pilot whales. Porpoises belong to their own family, Phocoenidae. Porpoises are different than dolphins. They have shorter snouts, trangular tops fin, and spade-shped teeth. This fact sheet focuses on dolphins in the family Delphinidae .
Streamlined bodies slip through the water.
A dolphin has streamlined body parts that help it swim easily through the water. The dorsal fin , located on the center of its back, is made of dense fibrous connective tissue - there is no bone inside. The dorsal fin acts as a keel, giving the dolphin some stability as it swims. Each lobe of a dolphin's tail is called a fluke . Like the dorsal fin, flukes have no bone or muscle inside.