New fossil penguins (Aves, Sphenisciformes) from the Oligocene of New Zealand reveal the skeletal plan of stem penguins

ABSTRACT

Three skeletons collected from the late Oligocene Kokoamu Greensand of New Zealand are among the most complete Paleogene penguins known. These specimens, described here as Kairuku waitaki, gen. et sp. nov., and Kairuku grebneffi, sp. nov., reveal new details of key elements of the stem penguin skeleton associated with underwater flight, including the sternum, flipper, and pygostyle. Relative proportions of the trunk, flippers, and hind limbs can now be determined from a single individual for the first time, offering insight into the body plan of stem penguins and improved constraints on size estimates for ‘giant’ taxa. Kairuku is characterized by an elongate, narrow sternum, a short and flared coracoid, an elongate narrow flipper, and a robust hind limb. The pygostyle of Kairuku lacks the derived triangular cross-section seen in extant penguins, suggesting that the rectrices attached in a more typical avian pattern and the tail may have lacked the propping function utilized by living penguins. New materials described here, along with re-study of previously described specimens, resolve several long-standing phylogenetic, biogeographic, and taxonomic issues stemming from the inadequate comparative material of several of the first-named fossil penguin species. An array of partial associated skeletons from the Eocene–Oligocene of New Zealand historically referred to Palaeeudyptes antarcticus or Palaeeudyptes sp. are recognized as at least five distinct species: Palaeeudyptes antarcticus, Palaeeudyptes marplesi, Kairuku waitaki, Kairuku grebneffi, and an unnamed Burnside Formation species.

ACKNOWLEDGMENTS

Field work was funded by grants to R.E.F. from New Zealand Geological Survey (1977), National Geographic Society (1989), and Otago Research Committee (1997). Thanks to M. A. Fordyce, A. Grebneff, and S. Munro for help in the field, and to the late D. Hulston, and B. and V. Williamson for access to sites and permission to collect. Preparation by C.M.J. and A. Grebneff was supported by Otago Research Grants to R.E.F.; thanks also to H. Pollock, J. A. Jensen, D. Bevin, and A. C. Begg for preparation. We thank P. Capainolo, J. Cracraft, B. Desjardens, M. Florence, C. Fraser, H. James, S. Heath, N. Hiller, C. Mehling, M. Norell, S. Olson, R. Salas, P. Scofield, P. Sweet, and A. Tennyson for access to specimens. Reviews by R. Scofield and P. Jadwiszczak and comments by T. Worthy improved the manuscript. Research was supported by NSF DEB grant 0949899 to D.T.K., an Otago Ph.D. Scholarship to T.A., and a travel grant from the Department of Geology, University of Otago to D.T.K.

Handling editor: Trevor Worthy

Notes

*The hindlimb shows signs of pathology (see text) so this value is considered unreliable.

**This specimen is abraded and so would have been slightly longer when complete.

***This is the largest specimen sufficiently intact to take the relevant measurements from the Seymour Island (Eocene, Antarctica) specimens reported by Jadwiszczak (2006b) who considered it to represent Anthropornis, Palaeeudyptes klekowskii, or Palaeeudyptes gunnari.