sentences:  As the name implies, they tend to be found in the open seas, unlike the river dolphins, although a few species such as the Irrawaddy dolphin are coastal or riverine.The Delphinidae are characterized by having distinct beaks (unlike the Phocoenidae), two or more fused cervical vertebrae and 20 or more pairs of teeth in their upper jaws.None is more than 4 m long.