Can. J. Zool. (1992)

DOI: 10.1139/z92-283


Structural modifications of the odontocete skull and nasal passages have shifted the position of the facial bones and associated soft anatomy to the dorsal aspect of the head. The facial structures of true porpoises, Phocoenidae, are highly specialized. Facial regions of 18 Phocoena phocoena and 3 Phocoenoides dalli specimens were dissected and described. In addition, heads of three phocoenid specimens were serially sectioned. Comparison to delphinid facial anatomy demonstrates that nasal passages, associated diverticula, and facial muscles of these phocoenid species are homologous to facial structures of delphinids, with several notable exceptions. The blowhole ligament and its posterior septum appear to be separate branches of the same structure; the structure of the blowhole ligament of delphinids may be a derived condition associated with the loss of the posterior septum. The potential functions of phocoenid facial structures are examined. Phocoenid nasal passages are capable of complex airflow. Sound transmission in phocoenids is suggested to be different from that in delphinids.