The 21 Basic Mammal Groups
Whales, Dolphins, and Porpoises (Order Cetacea)
Comprising close to a hundred species, cetaceans are divided into two main groups: toothed whales (which includes sperm whales, beaked whales, and killer whales, as well as dolphins and porpoises), and baleen whales, which includes right whales, bowhead whales, and the biggest cetacean of them all, the 200-ton blue whale. These mammals are characterized by their flipper-like forelimbs, reduced back limbs, nearly hairless bodies, and the single blowhole on top of their heads. The blood of cetaceans is unusually rich in hemoglobin, an adaptation that allows them to stay underwater for long periods of time.
The 21 Basic Mammal Group caches were placed for HNY21.