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During the 1995-1996 austral summer, exposures of the Fremouw and Falla Formations near the Shackleton Glacier were searched for fossil vertebrates. Initially, helicopter aerial reconnaissance was used to determine the best potential sites. Localities selected for field study included Collinson Ridge, Shenk Peak, and Halfmoon Bluff in the Cumulus Hills at the junction of the Shackleton and McGregor Glaciers; Schroeder Hill and Ellis Bluff farther up the Shackleton Glacier; and Kitching Ridge and Layman Peak on the opposite side of the Shackleton.
Only the lower portion of the Fremouw Formation (Early Triassic) produced vertebrates at any of the localities. In total, 120 specimens were collected from a number of places; however, the most productive site by far was Collinson Ridge. Numerous specimens were also collected at Halfmoon Bluff, and fewer came from Kitching Ridge and Shenk Peak. Only a single specimen was found at Layman Peak. Exposures at Schroeder Hill and Ellis Bluff were both stratigraphically higher than the other sites. Field analysis indicated that only the upper part of the Fremouw Formation and the lowest part of the Falla Formation were present in these sections. Although both Schroeder Hill and Ellis Bluff had an abundance of carbonized plant material, no vertebrates were found. The upper part of the Falla Formation that had produced Early Jurassic dinosaur material near the Beardmore Glacier (Hammer and Hickerson 1994; Hammer, Hickerson, and Slaughter 1994) was not found at any site near the Shackleton Glacier. Apparently sediments that young occur only on the highest peaks in the southern portion of the Transantarctic Mountains, which are all closer to the Beardmore area.
Although preparation of the vertebrates has just begun, preliminary analysis indicates the presence of both carnivorous and herbivorous therapsids. Small skulls and skeletons of diapsids (possibly eosuchians) as well as anapsids (including at least one type of procolophonid) have also been recognized. Finally, several taxa of small temnospondyl amphibians occur, including at least one lydekkerinid and a brachyopid (see table).
Collections made in previous years from the antarctic Fremouw Formation have included the therapsids Lystrosaurus, Myosaurus, Ericiolacerta, Pedaeosaurus, Rhigosaurus and Thrinaxodon, the eosuchian Prolacerta, the anapsid Procolophon, the lydekkerinid Cryobatrachus, the brachyopid Austrobrachyops, indeterminant rhytidosteid temnospondyls, and an indeterminant thecodont (Colbert 1982, pp. 11-35; Cosgriff and Hammer 1984; Hammer 1990, pp. 42-50). Whereas some specimens collected this past season appear to belong to these previously described taxa (particularly Lystrosaurus), others appear to represent new genera and/or genera not previously reported from Antarctica. In particular, the abundant amount of small anapsid, diapsid, and temnospondyl material includes specimens that do not belong to known antarctic genera.
As the table illustrates, the vertebrates were collected from more than one stratigraphic horizon at Kitching Ridge, Collinson Ridge, and Halfmoon Bluff. Although previous field seasons have shown vertebrates also occur in several horizons at Shenk Peak (Cosgriff and Hammer 1982), an unusually large portion of that section was under snow cover this past season, and the snow restricted collecting to a single horizon. The table also shows that the vertebrates occur in different facies. This study will include a faunal analysis of each horizon to determine if certain depositional settings preferentially preserve certain taxa, and/or if the distribution of some taxa are related to climate.
This research was supported by National Science Foundation grants OPP 93-15830 and OPP 93-15826 and by the Augustana Research Foundation. We wish to thank Rob Andress and Jason McKirahan for their help in the field.
References
Colbert, E.H. 1982. Triassic vertebrates in the Transantarctic Mountains. In M.D. Turner and J.F. Splettstoesser (Eds.), Geology of the central Transantarctic Mountains (Antarctic Research Series, Vol. 36). Washington, D.C.: American Geophysical Union.
Cosgriff, J.W., and W.R. Hammer. 1984. New material of labyrinthodont amphibians from the Lower Triassic Fremouw Formation of Antarctica. Journal of Vertebrate Paleontology, 4(1), 47-56.
Cosgriff, J.W., and W.R. Hammer. 1982. The pangean reptile Lystrosaurus McCaigi in the Lower Triassic of Antarctica. Journal of Paleontology, 56(2), 371-385.
Hammer, W.R. 1990. Triassic terrestrial vertebrate faunas of Antarctica. In T.N. Taylor and E.L. Taylor (Eds.), Antarctic paleobiology: Its role in the reconstruction of Gondwanaland. New York: Springer-Verlag.
Hammer, W.R., and W.J. Hickerson. 1994. A crested theropod dinosaur from Antarctica. Science, 264, 828-830.
Hammer, W.R., W.J. Hickerson, and R.W. Slaughter. 1994. A dinosaur assemblage from the Transantarctic Mountains. Antarctic Journal of the U.S., 29(5), 31-32.