Elasmosaurid plesiosaur remains containing gastroliths have been recently recovered from the Late Cretaceous Cape Lamb Member of the Snow Hill Island Formation, Antarctic Peninsula, as well as from the Sharon Springs Formation of the Pierre Shale Group, South Dakota. The significance of the Antarctic specimens lies in the large number and relatively small size of the stones, whereas those from South Dakota and elsewhere have larger stones but relatively small numbers. All specimens compared are of relatively large elasmosaurids, and rib diameters indicate similar overall size. One testable hypothesis was whether or not the weight of the gastroliths might be similar among similarly sized individuals. However, comparisons between the gastroliths recovered from an Antarctic specimen and those recovered from the Pierre Shale show great differences in both the size and number of gastroliths. The total mass of the stones collected in the specimen from Antarctica was 3.0 kg, whereas those recovered from the South Dakota specimens totaled 2.2 kg and 8.3 kg, respectively. Perhaps not all stones originally within each plesiosaur were found, but efforts were designed to recover every stone. The number of stones recovered from the Antarctic plesiosaur was exceptionally large (2626) and appears to represent the most gastroliths recovered from a single plesiosaur. Those recovered from South Dakota elasmosaurids totaled only 124 and 253, respectively. Therefore, neither weight nor number of stones corresponds among these large individuals, perhaps mirroring the temporal or behavioral differences. Lack of correspondence among individuals furthers questions concerning the utilization of gastroliths for neutral buoyancy, ballast, or as an aid in digestion. Many parameters remain unexplored, and questions arise not only as to the utilization of the gastroliths but also as to whether physiology of the Antarctic plesiosaurs differs from those at lower latitudes.

Abstract Considerable controversy exists concerning the stability of the Antarctic Ice Sheet during the Neogene Period. The northern Antarctic Peninsula is in a critical position in this debate as it represents a peripheral area of the ice sheet and is therefore likely to have been sensitive to climatic changes. This paper is concerned with Neogene glacial deposits that occur on James Ross and Vega islands. They occur between a thick volcanic sequence, the James Ross Island Volcanic Group, and Upper Cretaceous sedimentary rocks; they also occur within the volcanic sequence itself. The glacial deposits, where dated, give a series of snapshots of glacial conditions in Neogene time. The deposits are characterized by diamictite and sandy mudstone. Published 87 Sr/ 86 Sr ages on shelly fossils in some deposits range from 9.9 to 4.7 Ma, although additional 40 Ar/ 39 Ar ages on interbedded volcanic rocks suggest that younger sedimentary deposits are also present. On James Ross Island the basal diamictite is interpreted as glaciomarine sediment that has undergone subaqueous mass movement, and on Vega Island as basal till originating from the west. Provenance studies indicate that the Antarctic Peninsula Ice Sheet expanded sufficiently to deposit these sediments. These diamictites, in places, are overlain by waterlain tuffaceous rocks that include a minor ice-rafted component. Complex deformation of sedimentary and volcanic deposits and contact-metamorphism relationships confirm that volcanism was contemporaneous with glaciation. Later glacial events (within the volcanic sequence) are characterized by glacial erosion of basalt followed by basal till and, possibly, glaciofluvial deposition. The clasts in the latter are almost exclusively local, hence later glaciation was as a small ice cap constructed on the growing volcanic complex of James Ross Island.

Foraminiferal assemblages consisting of 76 genera and 145 species were recovered from Upper Cretaceous and Paleocene sediments in the James Ross Island region, northeastern Antarctic Peninsula. Open taxonomic nomenclature is used for 37 taxa and 10 new species are described, including Alveolophragmium macellarii, Spiroplectammina vegaensis, Dorothia paeminosa, Buliminella procera, Neobulimina digitata, Bolivina pustulata, Conorbina anderssoni, Cibicides nordenskjoldi, C. seymouriensis, and Anomalinoides larseni. Three biostratigraphic range zones are recognized for interregional and regional correlation: (1) the ?mid- to upper Campanian Gaudryina healyi Zone, used to correlate the Cape Lamb (Vega Island), The Naze (James Ross Island), Snow Hill, and lowermost Seymour Island beds; (2) the upper Campanian through Maastrichtian Hedbergella monmouthensis Zone, occurring only on Seymour Island; and the Danian Globastica daubjergensis Zone, also occurring only on Seymour Island. The foraminiferal transition from Upper Cretaceous to Lower Tertiary sediments on Seymour Island is characterized by extinction of all Upper Cretaceous planktonic species and numerous benthic taxa, a lowermost Tertiary dissolution facies that is barren of calcareous microfossils, and the appearance of the Danian marker species Globastica daubjergensis with low-diversity, high-dominance calcareous assemblages just above the dissolution facies. The stratigraphic distribution of foraminifera on Seymour Island attests to long-term environmental stability in the Upper Cretaceous sequence, in contrast to stressed environmental conditions in the lower Paleocene. Foraminiferal distributions indicate that the lowermost 250 m of the Seymour Island sequence was deposited in an inner neritic environment, and the overlying 950 m of Cretaceous and lower Danian sediments in an outer neritic setting. Foraminifera are absent from the younger Paleocene sequence, which was deposited in a relatively high-energy environment. The foraminiferal assemblages from the James Ross Island region include a mixture of cosmopolitan and provincial species. The Campanian-Maastrichtian fauna is characterized by: (1) the conspicuous absence of specialized benthic and keeled planktonic species, which are used as index fossils in low to middle latitude regions; (2) the predominance of long-ranging, cosmopolitan taxa; and (3) the occurrence of provincial species that were restricted to the southern, extratropical latitudes. These latter taxa are included in the foraminiferal Austral Province. The biogeographic distribution of Austral Province foraminifera supports the postulated trans-Antarctic seaways between East and West Antarctica and/or a marine communication through the Antarctic Peninsula during the Late Cretaceous. The Danian assemblages are characterized by opportunistic, cosmopolitan species and one new buliminellid species, which dominates the calcareous assemblages.

Rich palynomorph assemblages occur throughout the Campanian to Eocene stratigraphic section of Seymour and surrounding islands, northeastern Antarctic Peninsula. The section comprises sediments referred to the López de Bertodano, Sobral, Cross Valley, and La Meseta Formations. Nearshore marine to coastal-deltaic sediments include marine palynomorphs (dinoflagellate cysts, acritarchs, other algae) and diverse land-derived palynomorphs (pollen, spores, fungal spores, fresh-water algae), plus a variety of other organic debris. Palynostratigraphic results are based on a survey of about 530 outcrop samples of Campanian through Paleocene age. Six palynomorph zones, informally designated 1 through 6 and based on dinocyst species, are recognized in the upper Campanian through Paleocene section on Seymour Island. López de Bertodano sediments include zones 1 to 4 of late Campanian to Maastrichtian age. These Cretaceous zones are characterized by an evolving complex of dinocyst species of Manumiella and related genera. Zone 5, of early Paleocene age, occurs in uppermost López de Bertodano Formation sediments and most of the Sobral Formation on Seymour Island. Zone 6, of probable late Paleocene age, occurs in the uppermost Sobral Formation. Paleocene zones 5 and 6 are characterized by dinocysts Spinidinium spp., Deflandrea and Ceratiopsis spp., Microdinium sp.; and Paleoperidinium pyrophorum in zone 5. Two distinct older assemblages of middle to late Campanian age are recognized from The Naze, situated on northeastern James Ross Island, and Cape Lamb, on Vega Island. Upper Cretaceous-Paleocene nonmarine palynomorphs reflect a cool, humid, podocarpaceous conifer vegetation with a varied understory of ferns and highly endemic angiosperms.

Abstract A diverse marine assemblage of vertebrate fossils has been collected in recent years under the auspices of the British Antarctic Survey from Seymour, James Ross and Vega islands east of the Antarctic Peninsula. The specimens were derived from the Late Campanian Santa Marta Formation, Early Maastrichtian Snow Hill Island Formation and the Early–Late Maastrichtian López de Bertodano Formation. Sharks, teleosts, plesiosaurs and mosasaurs are represented, but birds and sea turtles are absent from the BAS collections; neornithine birds have been previously reported from the Late Cretaceous deposits of Antarctica. Shark teeth are relatively abundant, but teleosts are seemingly under-represented. Plesiosaurs (Elasmosauridae) are more abundant and complete than mosasaurs, and juveniles of both marine reptile groups are relatively common. The marine lizards, mosasaurs, are taxonomically diverse as elsewhere in the world, but with relatively few individuals compared to the plesiosaurs, which are taxonomically limited. A converse relationship normally occurs at other lower latitude Late Cretaceous localities. Some of these abundances and appearances may be due to collection bias, particularly due to difficult collecting conditions and weathering, but certain distributions may be the result of high latitudes.

Abstract Field expeditions to Seymour, James Ross and Vega islands, Antarctic Peninsula, have resulted in significant specimens of mosasaurs (marine lizards). Enough taxonomic diversity is now known to allow preliminary biostratigraphic assessment. These specimens were collected from the Late Campanian levels of the Santa Marta Formation and the Late Campanian–Late Maastrichtian López de Bertodano Formation. All specimens are from near-shore marine deposits, and an overall shallowing appears in younger successions. Most mosasaur individuals are represented by single specimens, but, in some cases, jaws and cranial material are preserved. Based on these specimens, tylosaurines appear in the Santa Marta Formation and extend into the López de Bertodano Formation, and Plioplatecarpines and mosasaurines occur in the upper López de Bertodano Formation. Therefore, the extent of mosasaur ranges in Antarctica is similar to that elsewhere in the world where the bulk of mosasaur differentiation occurred in the Campanian and Maastrichtian. Not enough specimens are available from the Campanian sedimentary rocks to determine whether the faunal turnover during the Campanian–Maastrichtian in North America exists in Antarctica. Some differences in taxa occur between Antarctica and elsewhere, but these are at generic levels, not subfamilial. Even so, most genera are similar, but the tylosaurines may be endemic, and, if the Moanasaurus reference is substantiated, this genus is also known only in New Zealand and Antarctica. Therefore, the ranges and occurrences of taxa suggest a mix of endemic and cosmopolitan genera. Additional field investigations are required to refine biostratigraphic ranges, and the ranges of many taxa such as those of Mosasaurus and Plioplatecarpus will be extended into older deposits.