Annalisa Berta is Professor in the Department of Biology at San Diego State University. She has served as the President of the Society of Vertebrate Paleontology, and Associate Editor of the scientific journal Marine Mammal Science.

Preface
Acknowledgments

1. Marine Mammals
Major Groups of Marine Mammals
Discovering, Naming, and Classifying Marine Mammals
Reconstructing the Hierarchy of Marine Mammals
Adaptations and Exaptations
What Is a Species and How Do New Species Form?
Where Do They Live and Why Are They Where They Are?

2. Past Diversity in Time and Space,Paleoclimates, and Paleoecology
Fossils and Taphonomy
The Discovery of the First Fossil Marine Mammal (a Whale)
The Importance of Fossils
How Do We Know the Age of a Fossil?
How Do We Know Where Marine Mammals Were?
Marine Mammal Diversity and Communities Through Time
What Led Marine Mammals Back to the Sea?

3. Pinniped Diversity, Evolution, and Adaptations
The Earliest Pinnipeds: Webbed Feet or Flippers?
Crown Pinnipeds
Desmatophocids: Extinct Phocid Relatives
Evolutionary Trends
Structural and Functional Innovations and Adaptations
Mating and Social Systems, Reproduction, and Life History

4. Cetartiodactylan Diversity, Evolution, and Adaptations
Early Whales Had Legs!
Crown Cetacea (Neoceti)
Evolutionary Trends
Structural and Functional Innovations and Adaptations
Mating and Social Systems, Reproduction, and Life History

5. Diversity, Evolution, and Adaptations of Sirenians
and Other Marine Mammals
Walking Sea Cows!
Crown Sirenia
Evolutionary Trends
Structural and Functional Innovations and Adaptations
Mating and Social Systems, Reproduction and Life History
Desmostylians
Aquatic Sloths
Marine Otters
Polar Bears

6. Ecology and Conservation
What Marine Mammals Eat and What Eats Them
Interactions Between Human and Marine Mammals:
Lessons Learned
Extinction: The Rule, Not the Exception

Glossary
Further Reading and Online Sources
Illustration Credits
Index

Return to the Sea portrays 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 nonspecialist. Against a backdrop of geologic time and changing climates and geography, this volume takes evolution as its unifying principle to help us to understand today's diversity of marine mammals and their responses to environmental challenges. Annalisa Berta explains current controversies and explores patterns of change now taking place, such as shifting food webs and predator-prey relationships, habitat degradation, global warming, and the effects of humans on marine-mammal communities.