The Cetacea order includes whales, porpoises and dolphins. It includes 90 species, some known only by a single specimen. The whales are the most popular, so this title focuses on them. By not including the porpoises and most of the dolphins, this poster is able to present larger images and informative facts about all whale species, such as the estimated world population. The false whales, such as the Killer Whale are also included, even though they are biologically classified as dolphins. Although whales are mammals, this poster does not show all of the Cetacean orders, thus it is not considered part of the Mammal series. Rather, it is part of our Sea Life Series.