With 32 species placed in 17 genera, this is by far the largest family of cetaceans. Delphinids are small to medium-sized cetaceans, ranging from about 1.5 m in length and 50 kg weight to almost 10 m in length and 7000 kg.
Males are usually larger than females.
This structure may help focus the sound emitted by these animals in echolocation and feeding. Other delphinids possess a melon, but their rostrum is short and the bulging forehead merely gives the head a squared-off appearance. The bodies of most species are sleek and streamlined. The group includes bottlenose dolphins, killer whales, pilot whales, Pacific striped dolphins, and many more. In the delphinid skull, the facial depression is broadly expanded.