Sexual Dimorphism

S Vertebrates ” ( J. G. M. Thewissen , and S. Nummela , eds ) , pp. 211 – 224 . University of California Press , Berkeley . Pihlström , H. ( 2008 ). Comparative anatomy and physiology of chemical senses in aquatic mammals . In “ Sensory Evolution on the Threshold Adaptations in Secondarily Aquatic Vertebrates ” ( J. G. M. Thewissen , and S. Nummela , eds ) , pp. 95 – 109 . University of California Press , Berkeley . Reuter , T. , and Peichl , L. ( 2008 ). Structure and function of the retina in aquatic tetrapods . In “ Sensory Evolution on the Threshold. Adaptations in Secondarily Aquatic Vertebrates ” ( J. G. M. Thewissen , and S. Nummela , eds ) , pp. 149 – 172 . University of California Press , Berkeley . Sonntag , C. F. ( 1922 ). The comparative anatomy of the tongues of the Mammalia. VII. Cetacea, Sirenia, and Ungulata . Proc. Zool. Soc. 44 , 639 – 657 . Spoor , F. , and Thewissen , J. G. M. ( 2008 ). Comparative and functional anatomy of balance in aquatic mammals . In “ Sensory Evolution on the Threshold, Adaptations in Secondarily Aquatic Vertebrates ” ( J. G. M. Thewissen , and S. Nummela , eds ) , pp. 257 – 284 . University of California Press , Berkeley . Verheyden , C. , and Jouventin , P. ( 1994 ). Olfactory behavior of foraging procellariiforms . Auk III , 285 – 291 . Wartzok , D. , and Ketten , D. R. ( 1999 ). Marine mammal sensory systems . In “ Biology of Marine Mammals ” ( J. E. Reynolds , III , and S. A. Rommel , eds ) , pp. 117 – 175 . Smithsonian Institution Press , Washington, D.C. . Wilkens , L. A. , and Hofmann , M. H. ( 2008 ). Electroreception . In “ Sensory Evolution on the Threshold, Adaptations in Secondarily Aquatic Vertebrates ” ( J. G. M. Thewissen , and S. Nummela , eds ) , pp. 325 – 332 . Univ. California Press , Berkeley .