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Return to the Sea

Return to the Sea: The Life and Evolutionary Times of Marine Mammals

Annalisa Berta
James L. Sumich
Carl Buell
Copyright Date: 2012
Edition: 1
Pages: 224
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  • Book Info
    Return to the Sea
    Book Description:

    Return to the Seaportrays the life and evolutionary times of marine mammals-from giant whales and sea cows that originated 55 million years ago to the deep diving elephant seals and clam-eating walruses of modern times. This fascinating account of the origin of various marine mammal lineages, some extinct, others extant but threatened, is for the non-specialist. Set against a backdrop of geologic time, changing climates, and changing geography, evolution is the unifying principle that helps us to understand the present day diversity of marine mammals and their responses to environmental challenges. Annalisa Berta explains current controversies and explores patterns of change taking place today, such as shifting food webs and predator-prey relationships, habitat degradation, global warming, and the effects of humans on marine mammal communities.

    eISBN: 978-0-520-95144-0
    Subjects: Zoology

Table of Contents

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  1. Front Matter
    (pp. i-vi)
  2. Table of Contents
    (pp. vii-x)
    (pp. xi-xii)
    (pp. xiii-xiv)
  5. CHAPTER ONE Marine Mammals An Introduction
    (pp. 1-28)

    Mammals, like nearly all other tetrapods (or four-legged animals), evolved on land. Marine mammals are a diverse assemblage of at least seven distinct evolutionary lineages of mammals that independently returned to the sea and include whales, dolphins, and porpoises (Cetartiodactylans); seals, sea lions, and walruses (Pinnipedia); sea cows (Sirenia); extinct sea cow relatives (Desmostylians); polar bears; sea and marine otters; and extinct aquatic sloths. The secondary adaptation of mammals to life in water required various morphological specializations, including for some lineages dramatic changes in body size and shape compared to their terrestrial relatives. Marine mammals are relatively large, with streamlined...

  6. CHAPTER TWO Past Diversity in Time and Space, Paleoclimates, and Paleoecology
    (pp. 29-50)

    In this chapter, I begin by introducing fossils and a geologic time frame and providing a context for interpreting marine mammal fossils and possible causes of their origin and diversification. Next, I consider the evolution of marine mammal communities through space and time and examine what may have led mammals back to the sea. Finally, I consider the use of a new technology, stable isotopes, for ecologic studies ranging from reconstructing paleotemperatures and climate change to documenting diet and foraging ecology among both extant and extinct marine mammals.

    In order to know where and when marine mammals originated and diversified,...

  7. CHAPTER THREE Pinniped Diversity, Evolution, and Adaptations
    (pp. 51-78)

    In this chapter, I trace the origin and evolutionary history of the major lineages of fossil and living pinnipeds and the major structural and functional innovations that shape their biology and behavior.

    Pinnipeds, or “fin-footed” carnivores, are divided into three groups: seals (phocids), fur seals and sea lions (otariids), and walruses (odobenids). There are 34–36 extant species of pinnipeds, excluding the Caribbean monk seal (Monachus tropicalis) and the Japanese sea lion (Zalophus japonicus), which only recently went extinct. Both species vanished due to human activities. The largest pinnipeds are elephant seals,Miroungaspecies, with males reaching more than 5...

  8. CHAPTER FOUR Cetartiodactylan Diversity, Evolution, and Adaptations
    (pp. 79-126)

    The name Cetartiodactyla reflects new discoveries that have revealed that whales are nested within even-toed ungulates (artiodactyls) such as hippopotamuses, giraffes, and deer. Two major groups of crown whales, or Cetacea (from the Greek wordcetusmeaningwhale), are recognized: toothed whales, or Odontoceti, and baleen whales, or Mysticeti. Toothed whales are considerably more diverse, with approximately 73 known species, compared to 14 mysticete species. Whales display considerable diversity in size (fig. 4.1), ranging from the blue whale, the largest animal on Earth (33 m or more than 100 ft in length, weighing 150 tons) to the vaquita (1.4 m...

  9. CHAPTER FIVE Diversity, Evolution, and Adaptations of Sirenians and Other Marine Mammals
    (pp. 127-150)

    Sirenians or sea cows include manatees (Trichechidae), comprising three species, and the Dugongidae, with a single species, the dugong. Sirenians derive their name from mermaids of Greek mythology, known as sirens. Although clearly not the original sirens discussed in the classic poemThe Odyssey, as the Greeks are unlikely to have encountered manatees or dugongs, early accounts of Columbus on a voyage in the Caribbean in 1493 described manatees as “sirens.” Sirenians are unique among living marine mammals by having an herbivorous diet, feeding almost entirely on aquatic plants. Like whales, they are totally aquatic but their ancestors had four...

  10. CHAPTER SIX Ecology and Conservation
    (pp. 151-174)

    Broad aspects of the biology of marine mammals are correlated with their ecological role—that is, how they make a living—and respond to the distribution of resources (for example, food and territory) and competitors in a community. This ecological role, explored in this chapter, includes food and the feeding relationship of marine mammals and the effects of change on the dynamics of marine ecosystems. Also considered is the influence of humans on marine mammal communities, ranging from oil spills and contamination of the ocean with heavy metals to diseases and global climate change and loss of habitat. Finally, conservation...

    (pp. 175-184)
    (pp. 185-190)
    (pp. 191-194)
  14. INDEX
    (pp. 195-206)
  15. Back Matter
    (pp. 207-207)