鸣谢照片版权持有人

照片按页中出现次序排列

American Museum of Natural History, New York, courtesy of: 58.

Animals Animals/OSF, New York: 143; Animals Animals/E. R. Degginger, 144 (1).

British Museum, London, courtesy of: 210 (1), 213 (1) (2), 219 (1); Reproduced by courtesy of the Trustees of the British Museum: 210 (2), 213 (3).

French National Museums, Louvre Museum, Paris: 212 (2).

© 1982 Ira Block/THE IMAGE BANK, New York: 12, 13.

Kentucky Department of Travel Development: 67.

Land Management, Bureau of, Washington, D.C.: 69 (2).

National Aeronautics and Space Administration, Washington, D.C.: 11, 128, 186 (2).

National Archives, Washington, D.C.: 126 (1) (2), 224 (1), 225 (4).

National Park Service, Washington, D.C.: 64 (1) Chukchi Imuruk.

National Zoological Park, Washington, D.C.: 4 (1)and 69 (4) Brandy Clymire.

© Outdoor Pictures, Washington State: 54, 68.

Smithsonian Institution, Washington, D.C.: 203 Photo Number 83-2259.

U.S. Fish & Wildlife Service, Washington, D.C.: 3 (3) Dean Biggins, 4 (2) William Hartgroves, 63 (2) Dean Biggins (3) Glen Smart, 64 (2) Dean Biggins (3) Dan Pfitzer, 68 (4) William Hartgroves, 69 (1) (3)Dean Biggins.

U.S. Geological Survey, Washington, D.C.: 225 (1).

Walters Art Gallery, Baltimore: 220.

World Health Organization: 224 (2) W. Cutting, 225 (2) Eric Schwab.