Key points are not available for this paper at this time.
Cetaceans-the whales, dolphins, and porpoises-are the taxonomically most diverse clade of aquatic mammals, with a fossil record going back at least to Middle Eocene time (52 Ma-millions of years before present) (Figure I). There are 75 to 77 living species in 1 3 or 1 4 families and two suborders: Mysticeti (baleen whales) and Odontoceti (toothed whales, dolphins, and porpoises) (Rice 1984, Evans 1 987). The extinct Archaeoceti are a third suborder. Extant cetaceans are ecologically diverse; sizes range from under 2 m to over 25 m, and habitats range from shelf and surface water to abyssal settings in tropical to polar oceans; some species live in fresh water. Living species attract marked public and scientific interest, but fossils also have an important role. The excellent fossil record helps us to understand morphological transition series and homologies of struc tures in living taxa. A resurgence of interest in anatomy has led to pion eering, albeit preliminary, cladistic analyses of fossil and extant Cetacea, with pivotal input from paleontologists. For a discussion of cladistics, see Padian et al ( 1 993) in this volume. Although volatile and clearly needing more study, the resulting classifications provide an adequate foundation for broader studies. Cetacean constructional morphology and related aspects of paleobiology are still in their infancy. Fossil taxa are potentially
Fordyce et al. (Sun,) studied this question.