The phylogeny of the living and fossil Sphenisciformes (penguins)

KSEPKA, D.T.; BERTELLI, S.; GIANNINI, N.P.; CLARKE, J.A.

Otawa

Congreso; 66th Annual Meeting of the Society of Vertebrate Paleontology; 2006

Society of Vertebrate Paleontology

We present the first phylogenetic analysis of the Sphenisciformes that extensively samples fossil taxa. Combined analysis of 182 morphological characters and sequence fragments from two mitochondrial genes (12S rDNA and cytochrome b) yields a largely resolved tree. The most basal sphenisciform taxa are relatively small fossil penguins, a result congruent with a volant ancestry for the clade. 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 paleogeographical reconstructions of the Southern continents positions. The breeding distribution of the ancestral node Sphenisciformes is reconstructed as occupying the Antarctic Peninsula. We stress that this area was located at significantly higher latitudes and closer to Tierra del Fuego during the Eocene than it is today. 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 be explained by dispersal along the paths of major ocean currents and the emergence of new islands due to tectonic events.