References Clemens, W. A. 1977. Phylogeny of marsupials. In B. Stonehouse and D. Gilmore (Eds.), The biology of marsupials. London: Macmillan Press Ltd. Marshall, L. C. 1980. Marsupial paleobiography. In L. Jacobs (Ed.), Aspects of vertebrate history. Flagstaff: Museum of Northern Arizona Press. Patterson, B., and Marshall, L. C. 1978. The Deseadan, early Oligocene, marsupiaha of South America. Fieldiana (Geology), 41, 37-100.

de Paula Couto, C. 1952. Fossil mammals from the beginning of the Cenozoic in Brazil. Marsupialia: Polydolopidae and Borhyaenidae. American Museum Novitates, 1559, 1-27.

Simpson, C. C. 1948. The beginning of the age of mammals in South America. Part 1. Bulletin of the American Museum of Natural History, 91,

1-232.

Tedford, R. H. 1974. Marsupials and the new biogeography. Society of Economic Mineralogists and Paleontologists Special Paper, 21, 109-126.

Zinsmeister, W. J. 1982. Late Cretaceous-Early Tertiary molluscan biogeography of the southern circum-Pacific. Journal of Paleontology, 56, 84-102.

Late Cretaceous marine vertebrates from Seymour Island, Antarctic Peninsula SANKAR CHATTERJEE

1.

The Museum Texas Tech University Lubbock, Texas 79409 WILLIAM J . ZINSMEISTER

Institute of Polar Studies Ohio State University Columbus, Ohio 43210

Geological fieldwork on Seymour Island during the 1981-82 austral summer led to the discovery of several interesting marine vertebrates from the Late Cretaceous Lopez de Bertodano Formation of the Marambio Group. These include bony fishes, sharks, and the reptilian suborders Plesiosauria and Mosasauria. The Lopez de Bertodano Formation consists of 1,067 meters of gently eastward-dipping, loosely consolidated sandstones and sandy siltstones which crop out in the southern two-thirds of Seymour Island. The invertebrate fauna is varied, consisting of ammonites, echinoids, bivalves, gastropods, and arthropods, and suggests Middle Campanian to possibly Maestrichtian Age (Rinaldi et al. 1978). Fish debris and bone fragments of marine reptiles were encountered occasionally, but due to incompleteness of the material the vertebrate remains, until recently, were not fully diagnostic. Abundant specimens of bony fishes (holosteans), including several skulls, were found for the first time. The shark specimens are represented by isolated teeth, a calcified jaw, and associated calcified vertebrae. The vertebrae are amphicoelous, short antero-posteriorly, showing concentric lamellae. Woodward (1906) referred similar vertebrae to the genus Ptychodus, but the identification has been questioned (Welton and Zinsmeister 1980). The first antarctic plesiosaur, represented by fragmentary material from the Late Cretaceous of James Ross Island, is of limited diagnostic value (del Valle, Medina, and de Brandoni 1977). The new material represents at least two individuals, one perhaps 7.5 meters long and the other up to 15 meters (figure). It consists of articulated vertebrae and associated girdle and limb elements, and we are hopeful that it will allow finer diagnosis. 66

The great marine reptile of the Late Cretaceous; this plesiosaur probably reached a length of 15 meters.

The presence of a mosasaur was also confirmed for the first time from Antarctica, from the Cretaceous of Seymour Island. The material includes a partial skull and associated procoelous vertebrae and limb elements. The abundance of vertebrates at Seymour Island ensures that further intensive collecting would serve both to greatly expand the faunal list and to acquire more morphologic information on the taxa already identified. This research is supported by National Science Foundation grants DPP 80-20096 and DPP 81-07152. We thank Gary P. Wilhite for assistance in the field, Nicholas Hotton for discussion, and Michael Nickell for illustration. References Rinaldi, C. A., Massabie, A., Morelli, J . , Roseman, H. L., and del Valle, R. A. 1978. Ceologia de la Isla Vicecomodoro Morambio. Direccion Nacional del Antarctico, Inst it uto Antarctico Argentino, Contribution 217, 5-43.

del Valle, R. A., Medina, R., and de Brandoni, A. C. 1977. Nota preliminar sobra el hallazgo de reptiles fosiles marinos de subordent Plesiosauria en las islas James Ross y Vega, Antartida. Direccion Nacional del Antarctico, Inst itufo Antarctico Argentino, Contribution 217, 1-13. Welton, B. J., and Zinsmeister, W. J. 1980. Eocene neoselachians from the La Meseta Formation, Seymour Island, Antarctic Peninsula. Contributions in Science, Natural History Museum of Los Angeles, Contribution 329, 1-10. Woodward, A. S. 1906. On fossil fish-remains from Snow Hill and Seymour Islands. Wissenschaftiche Ergebnisse der Schwedischen Shdpolur-

Expedition 1901-1903, 3(4), 1-4. ANTARCTIC JOURNAL