![]() ![]() These are clear signs of their mammalian heritage.Ĭetaceans are unrelated to other marine mammals, the sirenians (manatees and dugongs) and the pinnipeds (seals, sea lions, walruses). In spite of this, some species retain a few hairs on their face and in others the fetus has whiskers (Fig. ![]() However, all modern cetaceans lack a hair coat, presumably an adaptation to reduce friction and improve locomotion. The presence of hair or fur, for instance, is characteristic of mammals. Many features that are common in land mammals have changed in the evolutionary process that led to cetaceans. In spite of the variation in body size, all modern Cetacea are relatively similar in shape: they have a horizontal tail fluke used in swimming their forelimbs are flippers there are no external hind limbs their neck is short, and their body is streamlined.Ĭetaceans originated from land mammals (Thewissen and Williams 2002 Fordyce and Muizon 2001). ![]() Like other mammals and unlike other vertebrates, they nurse their young they have three ear bones that are involved in sound transmission (hammer, anvil, and stirrup), and their lower jaws consist of a single bone (the dentary).Ĭetacea includes one of the largest species of animal ever, the blue whale (27 m in length, 136,000 kg) but also has some very small modern representatives, e.g., the vaquita (1.4 m in length, 42 kg). All modern Cetacea live in water and cannot survive out of the water. Whales, dolphins, and porpoises together constitute the Cetacea (English: cetaceans). ![]()
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