MARINE MAMMAL SCIENCE, 22(4): 910–932 (October 2006) C 2006 by the Society for Marine Mammalogy DOI: 10.1111/j.1748-7692.2006.00080.x THE PHYLOGENETIC RELATIONSHIPS AND BIOGEOGRAPHY OF TRUE PORPOISES (MAMMALIA: PHOCOENIDAE) BASED ON MORPHOLOGICAL DATA LILIANA FAJARDO-MELLOR1 ANNALISA BERTA San Diego State University, Department of Biology, 5500 Campanile Drive, San Diego, California 92182, U.S.A. E-mail:
[email protected] ROBERT L. BROWNELL JR. Southwest Fisheries Science Center, 1352 Lighthouse Avenue, Pacific Grove, California 93950, U.S.A. CLAUDIA C. BOY R. NATALIE P. G OODALL Centro Austral de Investigaciones Cientıficas´ (CADIC), C.C. 92, 9410 Ushuaia, Tierra del Fuego, Argentina and Museo Acatushun´ de Aves y Mamıferos´ Marinos Australes, Estancia Harberton, 9410 Ushuaia, Tierra del Fuego, Argentina ABSTRACT Prior studies of phylogenetic relationships among phocoenids based on morphol- ogy and molecular sequence data conflict and yield unresolved relationships among species. This study evaluates a comprehensive set of cranial, postcranial, and soft anatomical characters to infer interrelationships among extant species and several well-known fossil phocoenids, using two different methods to analyze polymorphic data: polymorphic coding and frequency step matrix. Our phylogenetic results con- firmed phocoenid monophyly. The division of Phocoenidae into two subfamilies previously proposed was rejected, as well as the alliance of the two extinct genera Salumiphocaena and Piscolithax with Phocoena dioptrica and Phocoenoides dalli. Extinct phocoenids are basal to all extant species. We also examined the origin and distri- bution of porpoises within the context of this phylogenetic framework. Phocoenid phylogeny together with available geologic evidence suggests that the early history of phocoenids was centered in the North Pacific during the middle Miocene, with 1 Current address: East Carolina University, Brody School of Medicine, Department of Anatomy and Cell Biology, 600 Moye Boulevard, Greenville, North Carolina 27834, U.S.A.