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Abstrakt

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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Abstrakt

Defining species boundaries, due to morphological variation, often represents a significant challenge in paleozoology. In this paper we report results from multi− and univariate data analyses, such as enhanced clustering techniques, principal coordinates ordination method, kernel density estimations and finite mixture model analyses, revealing some morphometric patterns within the Eocene Antarctic representatives of Palaeeudyptes penguins. These large−sized birds were represented by two species, P. gunnari and P. klekowskii , known mainly from numerous isolated bones. Investigations focused on tarsometatarsi, crucial bones in paleontology of early penguins, resulted in a probability−based framework allowing for the “fuzzy” partitioning the studied specimens into two taxa with partly overlapping size distributions. Such a number of species was supported by outcomes from both multi− and univariate studies. In our opinion, more reliance should be placed on the quantitative analysis of form when distinguishing between species within the Antarctic Palaeeudyptes .
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Abstrakt

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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Abstrakt

The synsacrum is an important element of the axial skeleton in birds, both volant and flightless. Little is known about the maturation of this complex bone in penguins. In this work, the supposedly ontogenetically youngest known synsacrum of early penguins was described. The analysis of this specimen, collected within the Eocene La Meseta Formation of Seymour (Marambio) Island, Antarctic Peninsula, revealed that this bird had attained at least the fledging stage of growth. Studies of three mature synsacra recovered from the same formation focused on the synsacral canals and, using indirect reasoning, their contents. These analyses revealed that the lumbosacral intumescence of the spinal cord and its extensions, the transverse canals, had been developed roughly like those in extant penguins (and also swifts and cormorants). The neural spine extensions (a non−nervous tissue) tracing the transverse grooves of the dorsal wall of the synsacral canal are currently considered as involved in the control of walking. The presented data suggest that such a sense organ gained its current penguin configuration by the late Eocene.
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Abstrakt

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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Abstrakt

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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