The origin and evolutionary history of sirenians (manatees and dugongs) and their extinct relatives are reviewed in this chapter, in addition to sea and marine otters, polar bears, and evolutionary dead ends—aquatic sloths and desmostylians. Among structural and functional innovations and adaptations covered are the presence of body hairs and a lateral line sensory system in sirenians and the thick, dense fur of sea otters, which resulted in near extinction of the species. As the only herbivorous marine mammals, sirenians possess mobile lips and long digestive tracts, specialized for grazing on sea grasses. Various sirenian life history parameters, such as the longer time to reach sexual maturity and interbirth intervals of several years, have important conservation implications.
Keywords: manatees and dugongs; sea otters; polar bears; desmostylians; aquatic sloths; lateral line systems; herbivores; life history parameters and conservation implications
Chapter. 5356 words. Illustrated.
Subjects: Evolutionary Biology
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