Whales, Dolphins, and Porpoises [Proceedings] (1966)


(…) Flower (1883), in his search for the trenchant characters he needed to reach a decision about the arrangement of the Delphinidae, saw that the configuration of the pterygoid bones could be indicative. He contrasted the small, widely separated pterygoid hamuli of Monodon, Delphinapterus, and Phocoena with the large, inflated, closely juxtaposed hamuli of such forms as Tursiops and Delphinus. He also noted the existence of several intermediate positions. In effect, in the bony pterygoid hamuli he detected an evolutionary series that formed an important strut in the framework of his arrangement. Access to specimens in the flesh has provided some explanation of this progressive specialization in the pterygoid region, and has indeed, for the first time, made understandable the complicated topography of the ventral aspect of the cetacean cranium. From evidence obtained from specimens dissected or injected, the distribution of the middle-ear air sinuses in other forms not yet accessible for such treatment has been interpreted by the impressions made by the sinuses on bones adjacent to them; in some places the impression is no more than a change in the texture of the bone surface, while in others it amounts to partial or complete removal of the bone itself. I do not intend, however, to recapitulate the conclusions indicated in Fraser and Purves (1960), but rather to comment briefly on some of the species included in the arrangement and association of genera. (…)