The phylogeny of the living and fossil Sphenisciformes (penguins)

We present the first phylogenetic analysis of the Sphenisciformes that extensively samples fossil taxa. Combined analysis of 181 morphological characters and sequence fragments from mitochondrial and nuclear genes (12S, 16S, COI, cytochrome b, RAG-1) yields a largely resolved tree. Two species of the New Zealand Waimanu form a trichotomy with all other penguins in our result. The much discussed giant penguins Anthropornis and Pachydyptes are placed in two clades near the base of the tree. Stratigraphic and phylogenetic evidence suggest that some lineages of penguins attained very large body size rapidly and early in the clade's evolutionary history. The only fossil taxa that fall inside the crown clade Spheniscidae are fossil species assigned to the genus Spheniscus. Thus, extant penguin diversity is more accurately viewed as the product of a successful radiation of derived taxa than as an assemblage of survivors belonging to numerous lineages. The success of the Spheniscidae may be due to novel feeding adaptations and a more derived flipper apparatus. We offer a biogeographical scenario for penguins that incorporates fossil distributions and paleogeographic reconstructions of the Southern continent's positions. Our results do not support an expansion of the Spheniscidae from a cooling Continental Antarctica, but instead suggest those species that currently breed in that area are the descendants of colonizers from the Subantarctic. Many important divergence events in the clade Spheniscidae can instead be explained by dispersal along the paths of major ocean currents and the emergence of new islands due to tectonic events. (c) The Willi Hennig Society 2006.