• A number of ammonites were collected above the KIT References boundary as defined by dinocysts. This apparent di- achroneity of the KIT boundary between different groups of Zinsmeister, W.J. 1982. First U.S. expedition to the James Ross Island marine organisms highlights the problem of no formalized area, Antarctic Peninsula. Antarctic Journal of the U.S. 17(5), 63-64. Antarctic Jour- definition of the KIT boundary and illustrates the problem of Zinsmeister, W.J. 1985. 1985 Seymour Island Expedition. defining the KIT boundary in a section where there was con- nal of the U.S. 19(5), 41-42. tinuous deposition. This research was supported by National Science Foundation grant DPP 84-16783.

terrestrial bird, the first postcranial skeleton of a penguin-like New fossil vertebrates from Seymour bird, and a lower mandible of a small crocodilian. All of the Island, Antarctic Peninsula fossils were recovered from the La Meseta Formation of late Eocene age (approximately 40 million years old). The whale material comprises part of the skull and the ver- MICHAEL 0. WOODBURNE and JUDD A. CASE, tebrae and ribs of much of the thoracic region. The material is well preserved and shows that it pertains to a basiliosaurine, a member of the archaeocete (ancient-toothed whale) group. Ac- Department of Earth Sciences University of California cording to Ewan Fordyce, University of Otago, New Zealand, Riverside, California 92521 who collected the specimens, these remains constitute the best documentation of this kind of whale in the Southern Hemi- sphere. The animal, which apparently lived in shallow marine DAN S. CHANEY waters, may have been about 10 meters long. The specimens are now under study by Fordyce. U.S. National Museum A wide variety of nominally marine penguin-type birds has Smithsonian institution been recovered in this and past seasons from Seymour Island. Washington, D.C. 20560 The partial postcranial skeleton recovered this time will en- hance functional comparisons between these ancient birds and their modern counterparts. The 1986-1987 field season on Seymour Island (figure 1) A large (about 2 meters tall), predaceous terrestrial (flightless) yielded new remains of an extinct whale, a large flightless bird that apparently pertains to the phororhacoid group lived on Seymour Island in the late Eocene, as shown by a portion of its beak recovered this season (Case, Woodburne, and Chaney in press-a). The group is also known from South America, from SOBRAL FM the Oligocene to the present (Marshall 1978). Although modern representatives are about the size of a road-runner, the ancient RV-82001 birds were of large size and apparently filled the ecological SEYMOUR IS. L/ MESETA niche of a large carnivore in the Eocene and Oligocene. Al- I + + FM. though the legs were relatively slender, the body and head were / RV-8405 massive, as shown in reconstructions based on South American fossils (figure 2). A. H1 CROSS VALLEY FM The Seymour Island material pre-dates the known age of the group in South America, and some of the bird footprints re- LOPEZ de BE RTODANO ported from yet earlier Eocene (approximately 46 million years FORMATION SOBR ago) rocks on King George Island (Covacevich and Rich 1982; NNNNNNNNN FM Watts 1982) may pertain to this group, as well. In any case, the presence of such derived birds in the american and antarctic Southern Hemisphere indicates that their ancestors must have inhabited this region well before the time the fossils reported here were preserved. Furthermore, the flightless nature of these I I I I I birds requires a solid overland pathway by which they dis- 0 I 2 3 4 5 K persed between South America and peninsular Antarctica. This strengthens the proposals made earlier (Woodburne and Figure 1. Map of Seymour Island and the Antarctic Peninsula region. The La Meseta Formation is of late Eocene age. All other rock units Zinsmeister 1984; Case, Woodburne, and Chaney in press-b) are older (Late Cretaceous to Paleocene). Fossil localities produced for the existence of such a land connection, based on the pres- marsupials, crocodiles, and plants (RV-8200) and the phororhacoid ence in La Meseta rocks of two kinds of marsupials and bird (RV-8405). The whale site is just below the "F" in La Meseta Not hofagus (southern beech) plants. The presence in these same Formation. ("Km" denotes "kilometer? "Fm? denotes "formation.") deposits of small crocodiles is consistent with this proposal,

ANTARCTIC JOURNAL although the marine habitus of some modern crocodiles ren- ders the proposed terrestrial adaptation for the Seymour croco- dile a little more speculative. The Seymour Island form is, however, the first crocodilian known from Antarctica (Gas- parini 1980). This work is partially supported by National Science Founda- tion grants DPP 82-15493 and 85-21368. -Alm References

Case, J.A., M.O. Woodburne, and D.S. Chancy. In press-a. A gigantic phororhacoid (?) bird from Antarctica. Journal of Paleontology. Case, J.A., M.O. Woodburne, and D.S. Chaney. In press-b. A new genus of polydolopid marsupial from Seymour Island, Antarctic Peninsula; Paleogene differentiation of the land mammal fauna; land mammal dispersal in the southern hemisphere. In R.M. Feldmann and M . O. Woodburne (Eds.), (Geology and Paleontology of Seymour Island, Antarctic Peninsula.) (Geological Society of America, Memoir.) Covacevich, V., and P.V. Rich. 1982. New bird ichnites from Fildes Peninsula, King George Island, West Antarctica. In C. Craddock (Ed), Antarctic geoscience. Madison: University of Wisconsin Press. Gasparini, Z.de. 1980. South American Mesozoic Crocodiles. Mesozoic Vertebrate Life 1, 66-72. Marshall, L.G. 1978. The terror bird. Field Museum of Natural History Bulletin, 49, 6-15. Sinclair, W.J., and M.S. Farr. 1932. Ayes of the Santa Cruz beds. Reports - of the Princeton University Expeditions to Patagonia, q7(2), 157-238. Watts, D.R. 1982. Potassium-argon ages and paleomagnetic results from King George Island, south Shetland Islands. In C. Craddock, (Ed.), Antarctic geoscience. Madison: University of Wisconsin Press. Figure 2. Reconstruction of an extinct phororhacoid bird similar to Woodburne, MO., and W.J. Zinsmeister. 1984. The first land mammal the Seymour Island form (adapted from Sinclair and Farr, 1932, Plate from Antarctica and its biogeographic implications. Journal of Paleon- A). tology, 58(4), 913-948.

Late Cretaceous fossils from The Cretaceous strata is exposed on the steep slopes below the basaltic flows that cap the island. Talus from overlying Cockburn Island collected during the basalts cover most of the flanks of the island. The Cretaceous 1986-1987 expedition to the Antarctic sediments are exposed only in the small gullies cut through the Peninsula talus deposits. A section was measured through the Cretaceous

JEFFREY D. STILWELL and WILLIAM J. ZINSMEISTER

Department of Earth and Atmospheric Sciences Purdue University West Lafayette, Indiana 47907

During the Swedish South Polar Expedition 1901-1903, Nor- denskjoid (1905) and Andersson (1906) reported the occurrence of late Cretaceous and early Tertiary sediments on the flanks of Cockburn Island (figures 1 and 2). Although Cockburn Island (64°13S 56°50W) is only approximately 3.2 kilometers from Seymour Island, virtually no systematic work has been done on the island since Anderssons paper in 1906. During the course of the 1986-1987 expedition to Seymour Island, two excursions were made to Cockburn Island to investigate the stratigraphy Figure 1. Cockburn Island, Antarctic Peninsula. James Ross Island and paleontology of the Cretaceous and Tertiary strata. in background. View to the south.

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