Anatomy of the External Nasal Passages and Facial Complex in the Delphinidae (Mammalia: Cetacea)

Mead James G. Anatomy of the External Nasal Passages and Facial Complex in the Delphinidae (Mammalia: Cetacea). Smithsonian Contributions to Zoology, number 207, 72 pages, 26 figures, 3 tables, 1975.—This study is concerned with the comparative anatomy of the external nasal passages and associated structures in delphinid odontocetes. It has been possible to assemble detailed anatomical information for nearly all of the delphinid genera. Comparative data for the other small toothed whales is considered in such detail as is available. The function of the structures associated with the external nasal passages has been poorly understood, partly due to a lack of understanding of their anatomy. I have drawn functional conclusions from the basis of this comparative study, but these are largely unsupported by experimental data. The nasal musculature is concerned both with opening and closing the nasal passage during respiration, and with movement of air between the nasal diverticula during sound production. The nasal diverticula are part of the acoustic system of these animals, and function both as air reservoirs and as reflective elements to focus the emitted sound field. The potential area of sound production is limited to the deep structures around the external body nares. The melon probably serves as an acoustic channel. Cranial asymmetry in odontocetes is related to specialized sound-producing mechanisms involving predominantly the right nasal passage. The nasal structures have formed a very important functional complex in the evolution of odontocetes, and are important from a phyletic viewpoint. This study has shown that the genera Tursiops, Stenella, and Delphinus form a relatively generalized group within the Delphinidae. The bulbous-headed genera Grampus, Globicephala, and Pseudorca clearly represent independent specializations. The other families of odontocetes differ considerably from the delphinids in their facial anatomy. The anatomical diversity in this region suggests an acoustic diversity which remains to be demonstrated experimentally. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institution's annual report, Smithsonian Year. SI PRESS NUMBER 5387. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus). Library of Congress Cataloging in Publication Data Mead, James G. Anatomy of the external nasal passages and facial complex in the Delphinidae (Mammalia: Cetacea) (Smithsonian contributions to zoology, no. 207) Supt. of Docs, no.: SI 1.27:207 1. Delphinidae. 2. Nose. 3. Face. 4. Skull. I. Title. II. Series: Smithsonian Institution. Smithsonian contributions to zoology, no. 207. QL1.S54 no. 207 [QL737.C432] 591'.08s [599'.53] 75-619034