440 Piotr Jadwiszczak

EARLY EVOLUTION OF PENGUINS Summary

Penguins (Sphenisciformes) are extremely spe- America (Argentina, Chile and Peru). Significant cialized seabirds from the Southern Hemisphere. or dominant component of the fossil assemblages The fossil record of this order covers most of the were species characterized by large body size, of- Cenozoic. The oldest representatives of Sphenisci- ten clearly exceeding in this respect their modern formes come from the Paleocene of New Zealand relatives (fossil genera Anthropornis, Palaeeudyptes, (Waimanu manneringi and W. tuatahi) and the Pachydyptes, Icadyptes and Inkayacu). The consider- Antarctic Peninsula (Crossvallia unienwillia). These able body size was in some cases accompanied by archaic penguins were large flightless birds differing intriguing, from a functional point of view, mor- in terms of body shape from their modern counter- phological features, e.g. within the wing skeleton of parts. Moreover, several lines of evidence indicate the Antarctic Anthropornis. Interestingly, the only a lack of some adaptations within their locomotor penguin feather fossils (assignable to the Peruvian functional morphology and physiology that are typi- Inkayacu paracasensis) are Eocene in age. Climate cal of recent penguins. The next epoch, Eocene, was change, particularly severe cooling at the Eocene/ characterized by a remarkable morphological, taxo- Oligocene boundary, may have led to the disappear- nomic and ecological diversity of early Sphenisci- ance of penguins, for some 20 million years, from formes. The most numerous penguin remains have the known fossil record of Antarctic faunas. The been found in the Antarctic Peninsula. So far, four actual nature of this hiatus remains unknown, how- genera and ten species (excluding debatable taxa) ever. Oligocene penguins are known almost exclu- have been described. During Eocene, the recognized sively from New Zealand. range of this order expanded to Australia and South