Porpoises, Overview
This chapter discusses the origin, morphology, ecology, behavior, and conservation of porpoises. The porpoises are 1 of 10 families that constitute the suborder Odontoceti, or the modern toothed whales. The family Phocoenidae consists of six species, distributed in both hemispheres. The earliest porpoise known is Salumiphocaena stocktoni, discovered in late Miocene strata of southern California, approximately 11 million years ago. Analyses of the genome of living porpoises suggest that the finless porpoise (. Neophocaena phocaenoides) is the most primitive, or basal, member of the family. This view is consistent with morphological evidence. Porpoises share many morphological attributes that distinguish them from other small cetaceans. All six species are small, with no member of the family exceeding 250 cm in body length. Porpoises are stocky, robust animals, and lack the rostrum common to most delphinids. The appendages of most species are relatively small and, in the case of the finless porpoise, the dorsal fin is missing altogether. Porpoises are among the smallest and most paedomorphic cetaceans and these aspects of their biology are manifested in their reproductive biology. © 2009 Copyright © 2009 Elsevier Inc. All rights reserved.