Dolphins, whales, and seals belong to two orders of mammal adapted to living in water. Dolphins and whales make up the order Cetacea. Typical cetacean features include a streamlined, fishlike shape; forelimbs in the form of flippers; no visible hind limbs; a horizontally flattened tail; and thick blubber under the skin. There are two groups of cetaceans: toothed whales, including sperm whales, white whales, beaked whales, dolphins, and porpoises; and the larger whalebone (baleen) whales, including rorquals, gray whales, and right whales. The blue whale—a rorqual—is the largest living animal: an adult may be up to 100 ft (30 m) long and weigh 145 tons (130 metric tons). Seals and their relatives—sea lions and walruses—make up the order Pinnipedia. Characteristically, they have a streamlined, torpedo-shaped body; forelimbs and hind limbs modified as flippers; thick blubber; and no external ears.
Dolphins, whales, and seals belong to two orders of mammal adapted to living in water. Dolphins and whales make up the order Cetacea. Typical cetacean features include a streamlined, fishlike shape; forelimbs in the form of flippers; no visible hind limbs; a horizontally flattened tail; and thick blubber under the skin. There are two groups of cetaceans: toothed whales, including sperm whales, white whales, beaked whales, dolphins, and porpoises; and the larger whalebone (baleen) whales, including rorquals, gray whales, and right whales. The blue whale—a rorqual—is the largest living animal: an adult may be up to 100 ft (30 m) long and weigh 145 tons (130 metric tons). Seals and their relatives—sea lions and walruses—make up the order Pinnipedia. Characteristically, they have a streamlined, torpedo-shaped body; forelimbs and hind limbs modified as flippers; thick blubber; and no external ears.
