New fossil vertebrates from Seymour Island, Antarctic Peninsula
• A number of ammonites were collected above the KIT boundary as defined by dinocysts. This apparent diachroneity of the KIT boundary between different groups of marine organisms highlights the problem of no formalized definition of the KIT boundary and illustrates the problem of defining the KIT boundary in a section where there was continuous deposition. This research was supported by National Science Foundation grant DPP 84-16783.
New fossil vertebrates from Seymour Island, Antarctic Peninsula MICHAEL 0. WOODBURNE and JUDD A. CASE, Department of Earth Sciences University of California Riverside, California 92521
DAN S. CHANEY U.S. National Museum Smithsonian institution Washington, D.C. 20560
The 1986-1987 field season on Seymour Island (figure 1) yielded new remains of an extinct whale, a large flightless
SOBRAL FM
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RV-82001
SEYMOUR IS.
A.
I
L/ MESETA + + FM.
/ RV-8405 CROSS VALLEY FM
LOPEZ de BE RTODANO FORMATION SOBR NNNNNNNNN FM
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Figure 1. Map of Seymour Island and the Antarctic Peninsula region. The La Meseta Formation is of late Eocene age. All other rock units are older (Late Cretaceous to Paleocene). Fossil localities produced marsupials, crocodiles, and plants (RV-8200) and the phororhacoid bird (RV-8405). The whale site is just below the "F" in La Meseta Formation. ("Km" denotes "kilometer?' "Fm?' denotes "formation.")
References Zinsmeister, W.J. 1982. First U.S. expedition to the James Ross Island area, Antarctic Peninsula. Antarctic Journal of the U.S. 17(5), 63-64. Zinsmeister, W.J. 1985. 1985 Seymour Island Expedition. Antarctic Journal of the U.S. 19(5), 41-42.
terrestrial bird, the first postcranial skeleton of a penguin-like bird, and a lower mandible of a small crocodilian. All of the 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 vertebrae 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. According to Ewan Fordyce, University of Otago, New Zealand, who collected the specimens, these remains constitute the best documentation of this kind of whale in the Southern Hemisphere. The animal, which apparently lived in shallow marine waters, may have been about 10 meters long. The specimens are now under study by Fordyce. A wide variety of nominally marine penguin-type birds has been recovered in this and past seasons from Seymour Island. The partial postcranial skeleton recovered this time will enhance functional comparisons between these ancient birds and their modern counterparts. A large (about 2 meters tall), predaceous terrestrial (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 the Oligocene to the present (Marshall 1978). Although modern representatives are about the size of a road-runner, the ancient birds were of large size and apparently filled the ecological niche of a large carnivore in the Eocene and Oligocene. Although the legs were relatively slender, the body and head were massive, as shown in reconstructions based on South American fossils (figure 2). The Seymour Island material pre-dates the known age of the group in South America, and some of the bird footprints reported from yet earlier Eocene (approximately 46 million years ago) rocks on King George Island (Covacevich and Rich 1982; 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 birds requires a solid overland pathway by which they dispersed between South America and peninsular Antarctica. This strengthens the proposals made earlier (Woodburne and Zinsmeister 1984; Case, Woodburne, and Chaney in press-b) for the existence of such a land connection, based on the presence in La Meseta rocks of two kinds of marsupials and Not hofagus (southern beech) plants. The presence in these same deposits of small crocodiles is consistent with this proposal, ANTARCTIC JOURNAL
although the marine habitus of some modern crocodiles renders the proposed terrestrial adaptation for the Seymour crocodile a little more speculative. The Seymour Island form is, however, the first crocodilian known from Antarctica (Gasparini 1980). This work is partially supported by National Science Foundation 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.)
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Figure 2. Reconstruction of an extinct phororhacoid bird similar to the Seymour Island form (adapted from Sinclair and Farr, 1932, Plate A).
Late Cretaceous fossils from Cockburn Island collected during the 1986-1987 expedition to the Antarctic Peninsula
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. A y es 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. Woodburne, MO., and W.J. Zinsmeister. 1984. The first land mammal from Antarctica and its biogeographic implications. Journal of Paleontology, 58(4), 913-948.
The Cretaceous strata is exposed on the steep slopes below the basaltic flows that cap the island. Talus from overlying basalts cover most of the flanks of the island. The Cretaceous sediments are exposed only in the small gullies cut through the 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, Nordenskjoid (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°13'S 56°50'W) is only approximately 3.2 kilometers from Seymour Island, virtually no systematic work has been done on the island since Andersson's 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 and paleontology of the Cretaceous and Tertiary strata. 1987 REVIEW
Figure 1. Cockburn Island, Antarctic Peninsula. James Ross Island in background. View to the south. 5
New fossil vertebrates from Seymour Island, Antarctic Peninsula MICHAEL 0. WOODBURNE and JUDD A. CASE, Department of Earth Sciences University of California Riverside, California 92521
DAN S. CHANEY U.S. National Museum Smithsonian institution Washington, D.C. 20560
The 1986-1987 field season on Seymour Island (figure 1) yielded new remains of an extinct whale, a large flightless
SOBRAL FM
H1
RV-82001
SEYMOUR IS.
A.
I
L/ MESETA + + FM.
/ RV-8405 CROSS VALLEY FM
LOPEZ de BE RTODANO FORMATION SOBR NNNNNNNNN FM
I I I I I 0 I 2 3 4 5 K
Figure 1. Map of Seymour Island and the Antarctic Peninsula region. The La Meseta Formation is of late Eocene age. All other rock units are older (Late Cretaceous to Paleocene). Fossil localities produced marsupials, crocodiles, and plants (RV-8200) and the phororhacoid bird (RV-8405). The whale site is just below the "F" in La Meseta Formation. ("Km" denotes "kilometer?' "Fm?' denotes "formation.")
References Zinsmeister, W.J. 1982. First U.S. expedition to the James Ross Island area, Antarctic Peninsula. Antarctic Journal of the U.S. 17(5), 63-64. Zinsmeister, W.J. 1985. 1985 Seymour Island Expedition. Antarctic Journal of the U.S. 19(5), 41-42.
terrestrial bird, the first postcranial skeleton of a penguin-like bird, and a lower mandible of a small crocodilian. All of the 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 vertebrae 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. According to Ewan Fordyce, University of Otago, New Zealand, who collected the specimens, these remains constitute the best documentation of this kind of whale in the Southern Hemisphere. The animal, which apparently lived in shallow marine waters, may have been about 10 meters long. The specimens are now under study by Fordyce. A wide variety of nominally marine penguin-type birds has been recovered in this and past seasons from Seymour Island. The partial postcranial skeleton recovered this time will enhance functional comparisons between these ancient birds and their modern counterparts. A large (about 2 meters tall), predaceous terrestrial (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 the Oligocene to the present (Marshall 1978). Although modern representatives are about the size of a road-runner, the ancient birds were of large size and apparently filled the ecological niche of a large carnivore in the Eocene and Oligocene. Although the legs were relatively slender, the body and head were massive, as shown in reconstructions based on South American fossils (figure 2). The Seymour Island material pre-dates the known age of the group in South America, and some of the bird footprints reported from yet earlier Eocene (approximately 46 million years ago) rocks on King George Island (Covacevich and Rich 1982; 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 birds requires a solid overland pathway by which they dispersed between South America and peninsular Antarctica. This strengthens the proposals made earlier (Woodburne and Zinsmeister 1984; Case, Woodburne, and Chaney in press-b) for the existence of such a land connection, based on the presence in La Meseta rocks of two kinds of marsupials and Not hofagus (southern beech) plants. The presence in these same deposits of small crocodiles is consistent with this proposal, ANTARCTIC JOURNAL
although the marine habitus of some modern crocodiles renders the proposed terrestrial adaptation for the Seymour crocodile a little more speculative. The Seymour Island form is, however, the first crocodilian known from Antarctica (Gasparini 1980). This work is partially supported by National Science Foundation 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.)
-
Figure 2. Reconstruction of an extinct phororhacoid bird similar to the Seymour Island form (adapted from Sinclair and Farr, 1932, Plate A).
Late Cretaceous fossils from Cockburn Island collected during the 1986-1987 expedition to the Antarctic Peninsula
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. A y es 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. Woodburne, MO., and W.J. Zinsmeister. 1984. The first land mammal from Antarctica and its biogeographic implications. Journal of Paleontology, 58(4), 913-948.
The Cretaceous strata is exposed on the steep slopes below the basaltic flows that cap the island. Talus from overlying basalts cover most of the flanks of the island. The Cretaceous sediments are exposed only in the small gullies cut through the 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, Nordenskjoid (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°13'S 56°50'W) is only approximately 3.2 kilometers from Seymour Island, virtually no systematic work has been done on the island since Andersson's 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 and paleontology of the Cretaceous and Tertiary strata. 1987 REVIEW
Figure 1. Cockburn Island, Antarctic Peninsula. James Ross Island in background. View to the south. 5
