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Number of results: 11
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Abstract

Remains referred to Phorusrhacidae from the Cretaceous and Paleogene of the Antarctic Peninsula, and mainly known through informal and succinct descriptions, are reassigned here to other bird lineages recorded in the Antarctic continent. New records of ratites, pelagornithid birds, and penguins are added to the Upper Eocene avifauna of Seymour Island. Moreover, the original allocation for an alleged cursorial seriema−like bird from the Maastrichtian of Vega Island is refuted, and its affinities with foot−propelled diving birds are indicated. The indeterminate Pelagornithidae specimen represents the largest pseudo−toothed bird known so far. It is concluded that there is no empirical evidence for the presence of terror birds in Antarctica.
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Abstract

Isolated and fragmented jaws, a single basioccipitale and vertebrae of the Gadiformes, indeterminate family and genus, are described from Eocene sediments of the La Meseta Formation, Seymour Island, Antarctic Peninsula. Based on the dentition and other characters of both jaws they are assigned an informal name of „Mesetaichthys". The remaining isolated bones belong probably to the same form.
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Abstract

Early Palaeocene through early Eocene silicoflagellate assemblages were examined from five southern subtropical through subpolar deep-sea sites: DSDP Holes 208 and 524, and ODP Holes 700B, 752A, and 1121B. For each site, the taxonomic composition of the silicoflagellate assemblage is documented in detail; Pseudonaviculopsis gen. nov., Dictyocha castellum sp. nov. and Stephanocha? fulbrightii sp. nov. are proposed, along with several new combinations. More importantly, however, these observations enable a considerable refinement to the existing Palaeocene–Eocene silicoflagellate biostratigraphic zonation that for the first time uses datums calibrated to the Geomagnetic Polarity Timescale. The Corbisema aspera Interval Zone occurs immediately above the K/Pg boundary and is here described from Seymour Island. The Corbisema hastata Partial Range Zone extends from near the K/Pg boundary to late early Palaeocene and has been observed in Hole 208. The Pseudonaviculopsis disymmetrica Acme Zone occurs in Holes 208 and 700B. The Dictyocha precarentis Partial Range Zone, observed in Holes 208, 700B, 752A and 1121B, is subdivided into D. precarentis, Naviculopsis primativa, N. cruciata and Pseudonaviculopsis constricta subzones. The Naviculopsis constricta Partial Range Zone occurs in Holes 524, 700B, 752A and 1121B. This study is also the first to consider syn- and/or diachroneity in Palaeogene silicoflagellate biostratigraphy.
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Abstract

The tarsometatarsus, a compound bone from the lower leg in birds, is the most important skeletal element in fossil penguin taxonomy, especially in the case of early members of this group. However, any attempt to go beyond the problem of mere classification obviously requires the better understanding of osteological traits under consideration. This in turn touches on the issue of interplay between bone and concomitant soft−tissue structures, such as muscles, tendons and vessels. This paper focuses on the more holistic comprehension of the tarsometatarsal section of the Eocene penguin foot, based on the analysis of the myology and the vascular system of its modern counterparts. A number of graphical reconstructions are provided with a discussion of the role of the hypotarsus and inter− metatarsal foramina.
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Abstract

Pyrite framboids occur in loose blocks of plant−bearing clastic rocks related to volcano−sedimentary succession of the Mount Wawel Formation (Eocene) in the Dragon and Wanda glaciers area at Admiralty Bay, King George Island, West Antarctica. They were investigated by means of optical and scanning electron microscopy, energy−dispersive spectroscopy, X−ray diffraction, and isotopic analysis of pyritic sulphur. The results suggest that the pyrite formed as a result of production of hydrogen sulphide by sulphate reducing bacteria in near surface sedimentary environments. Strongly negative #2;34SVCDT values of pyrite (−30 – −25 ‰) support its bacterial origin. Perfect shapes of framboids resulted from their growth in the open pore space of clastic sediments. The abundance of framboids at cer− tain sedimentary levels and the lack or negligible content of euhedral pyrite suggest pulses of high supersaturation with respect to iron monosulphides. The dominance of framboids of small sizes (8–16 μm) and their homogeneous distribution at these levels point to recurrent development of a laterally continuous anoxic sulphidic zone below the sediment surface. Sedimentary environments of the Mount Wawel Formation developed on islands of the young magmatic arc in the northern Antarctic Peninsula region. They embraced stagnant and flowing water masses and swamps located in valleys, depressions, and coastal areas that were covered by dense vegetation. Extensive deposition and diagenesis of plant detritus in these environments promoted anoxic conditions in the sediments, and a supply of marine and/or volcanogenic sulphate enabled its bacterial reduction, precipitation of iron mono− sulphides, and their transformation to pyrite framboids.
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Abstract

The loose, small zooecia of the cheilostome bryozoans have been discovered in the lowermost part of the La Meseta Formation on Seymour (Marambio) Island. They systematically include the representatives of Beanidae Canu et Bassler, Catenicellidae Busk, Savignyellidae Levinsen, and Calwelliidae MacGillivra y. The bryozoan assemblage is comprised of separate, small−sized internal moulds dominated by distinct, boat−shaped zooecia belonging to Beania , scarce, unizooidal internodes tentatively included into a ditaxiporine catenicellid ? Vasignyella , and representative of the family Savignyellidae. A few branched segments composed of multiserial zooecia arranged back to back were tentatively incorporated into ? Malakosaria . Beania , marks the oldest fossil record, whereas representatives of Savignyellidae along with ditaxiporine catenicellid and ? Malakosaria are for the first time reported from Antarctica. The relationship between the taxonomic composition, colony growth−patterns rep− resented by membraniporiform/petraliform, catenicelliform and cellariform, along with associated biota and sedimentary structures of the La Meseta Formation implies nearshore environment, with considerable wave action, and warm climatic conditions.
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Abstract

The only record of the Paleogene Antarctic Sphenisciformes comes from the Eocene La Meseta Formation (Seymour Island, Antarctic Peninsula). The analysis of tarso− metatarsi attributed to the genus Anthropornis (“giant” penguins) from the Argentine, Polish and Swedish collections revealed an intriguing heterogeneity within these taxonomically important elements of the skeleton. The unique hypotarsal morphology challenges the current systematics of large−bodied penguins and sheds new light on their evolution.
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Abstract

The fossil record of Antarctic Sphenisciformes dates as early as the late Palaeocene Cross Valley Formation, Seymour Island, Antarctic Peninsula. However, the best known Antarctic locality for early penguin remains (mainly isolated bones) is the Eocene La Meseta Formation that outcrops in the northeast of Seymour Island. The analysis of an unstudied set of specimens collected there by members of the British Antarctic Survey in 1989 has resulted in identification of a distal humerus from the unit Telm3 (early Eocene) of the formation that is the oldest known bone attributable to a medium−sized (in the context of the entire Cainozoic era) penguin. This find suggests that the origin of these birds, in con− junction with an increase in taxonomic diversity of the Eocene Sphenisciformes, was related to the Early Eocene Climatic Optimum (EECO) or, more probably, the early phase of subsequent cooling.
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Abstract

The fossil record of the Antarctic penguins is dated to the late Paleocene of Seymour (Marambio) Island, but the largest sphenisciforms, genera Anthropornis and Palaeeudyptes , originate from the Eocene La Meseta Formation. Here, the most complete large−scale reconstruction of a limb skeleton (a whole wing and a partial hind leg) of a Paleogene Antarctic penguin is reported. All bones are attributable to a single individual identified as Anthropornis sp. The comparative and functional analyses of the material indicate that this bird was most probably well−adapted to land and sea while having a number of intriguing features. The modern−grade carpometacarpal morphology is unique among known Eocene Antarctic species and all but one more northerly taxa.
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Abstract

Radiometric and geochemical studies were carried out at Red Hill in the southern part of King George Island (South Shetland Islands, northern Antarctic Peninsula) on the Bransfield Strait coast. The rock succession at Red Hill has been determined to represent the Baranowski Glacier Group that was previously assigned a Late Cretaceous age. Two formations were distinguished within this succession: the lower Llano Point Formation and the upper Zamek Formation. These formations have stratotypes defined further to the north on the western coast of Admiralty Bay. On Red Hill the Llano Point Formation consists of terrestrial lavas and pyroclastic breccia; the Zamek Formation consist predominantly of fine to coarse tuff, pyroclastic breccia, lavas, tuffaceous mud− , silt−, and sandstone, locally conglomeratic. The lower part of the Zamek Formation contains plant detritus (Nothofagus , dicotyledonous, thermophilous ferns) and numerous coal seams (vitrinitic composition) that confirm the abundance of vegetation on stratovolcanic slopes and surrounding lowlands at that time. Selected basic to intermediate igneous rocks from the succession have been analysed for the whole−rock K−Ar age determination. The obtained results indicate that the Red Hill succession was formed in two stages: (1) from about 51–50 Ma; and (2) 46–42 Ma, i.e. during the Early to Middle Eocene. This, in combination with other data obtained from other Baranowski Glacier Group exposures on western coast of Admiralty Bay, confirms the recently defined position of the volcano−clastic succession in the stratigraphic scheme of King George Island. The new stratigraphic position and lithofacies development of the Red Hill succession strongly suggest its correlation with other Eocene formations containing fossil plants and coal seams that commonly occur on King George Island.
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Abstract

New evidence of Eocene preglacial environments has been found on the southern coast of Ezcurra Inlet on King George Island, South Shetland Islands, West Antarctica. Plant remains (trunks, leaves, detritus) and carbonaceous seams and beds occur in sedimentary strata in a 4 km long Cytadela outcrop of the Point Thomas Formation. They are an evidence for the presence and diversity of terrestrial vegetation in the northern Antarctic Peninsula region. The forests were composed mostly of Podocarpaceae– Araucaria – Nothofagus , with an undergrowth of hygrophilous and thermophilous ferns, and grew on volcanic slopes and surrounding lowland areas of King George Island during breaks in volcanic activity. The succession that crops out at Cytadela provides a record of changing climatic conditions from a warm and wet climate with extensive vegetation to a much drier climate with limited vegetation and ubiquitous weathering of volcanic bedrock. The geochemical indices of weathering (CIA, PIA and CIW) have narrow and relatively high value ranges (76–88), suggesting moderate to high chemical weathering under warm and humid climate conditions. The decrease in humidity and the decline in plant life through the succession can be related to the gradually cooling climate preceding development of the Oligocene ice cover across the Antarctic continent.
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