Cetacean Evolution

Abstract

Observations on living and fossil whales and dolphins allow many inferences about cetacean evolution and extinction. Molecular phylogenetic methods cluster living species into clades, generally given formal taxonomic names. Fossils span 50+ million year, and reveal many extinct groups that helped shape the evolution of living lineages. Fossils indicate at least three major radiations—evolutionary changes in diversity, geographic distribution, feeding mode, and habitat. Functional studies of modern and fossil species help to understand such evolutionary-ecological changes. Cetacean evolution has been fine-tuned by natural selection operating on biological processes such as sexual selection and mimicry. Evolution has also been governed by physical aspects of the oceans, as revealed by, e.g., north-south, polar, and riverine distribution patterns. For living Cetacea, odontocetes are markedly more diverse than mysticetes; the ocean dolphins (Delphinidae) dominate diversity, followed by beaked whales and by rorquals.