ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    facet.materialart.
    Unknown
    A new basal actinopterygian fish from the Middle Devonian Aztec Siltstone of Antarctica (2008)
    Cambridge University Press
    Details
    Publication Date: 2008-03-27
    Description: A new basal actinopterygian fish, Donnrosenia schaefferi gen. et sp. nov., is described from the Middle Devonian (Givetian) Aztec Siltstone of southern Victoria Land, Antarctica. Donnrosenia gen. nov. is characterized by the large parietals which are of almost equivalent size to the frontals, very small intertemporals, a small accessory operculum situated dorsally to the prominent anterodorsal process of the suboperculum, a deep dentary with anterior flexure, porous ornamentation on the clavicle, an elongate body form with macromeric squamation, an absence of paired fringing fulcra on the fins, and pectoral lepidotrichia which are unsegmented for much of their length. A phylogenetic analysis based on dermal skeletal features of Devonian actinopterygians indicates that Donnrosenia gen. nov. is the sister taxon to Howqualepis from the Middle Devonian of Victoria, Australia, and is embedded within a possible clade containing the actinopterygians from the Gogo Formation, Western Australia. This supports the concept of an endemic radiation of East Gondwanan actinopterygians, and reinforces the already strong biogeographical similarities between the Middle Devonian palaeofaunas of Australia and Antarctica.
    Print ISSN: 0954-1020
    Electronic ISSN: 1365-2079
    Topics: Biology , Geography , Geosciences
    Published by Cambridge University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 2
    facet.materialart.
    Unknown
    Phyllolepid placoderm fish remains from the Devonian Aztec Siltstone, southern Victoria Land, Antarctica (2005)
    Cambridge University Press
    Details
    Publication Date: 2005-08-17
    Description: Phyllolepid placoderm remains from the Aztec Siltstone fish fauna are described as Austrophyllolepis quiltyi sp. nov., Austrophyllolepis cf. A. youngi, Placolepis tingeyi sp. nov., and phyllolepid indet. The new Antarctic species of two genera previously only known from Australia reinforce evidence from other fish taxa of close biogeographic affinity, as part of the eastern margin of Palaeozoic Gondwana. At least three genera and four species gives the Aztec Siltstone fish fauna the most diverse phyllolepid assemblage known, and probably the oldest documented so far (?late Middle Devonian). Specimens of Austrophyllolepis from the type locality at Mount Howitt, Victoria, are refigured for comparison with the Antarctic species. The order Phyllolepida is a key group for understanding Devonian vertebrate biogeography and palaeogeography, with a unique disjunct distribution in both time and space between the Southern and Northern hemispheres. Phyllolepids document one of the major dispersal events in early vertebrate history, which approximately coincided with the Frasnian–Famennian boundary mass extinction during the Late Devonian.
    Print ISSN: 0954-1020
    Electronic ISSN: 1365-2079
    Topics: Biology , Geography , Geosciences
    Published by Cambridge University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 3
    facet.materialart.
    Unknown
    Disarticulated acanthodian and chondrichthyan remains from the upper Middle Devonian Aztec Siltstone, southern Victoria Land, Antarctica (2008)
    Cambridge University Press
    Details
    Publication Date: 2008-09-04
    Description: Well-preserved vertebrate microremains are abundant in the residues from a calcareous grey siltstone in the karawaka biozone (?late Givetian) of the Aztec Siltstone at Mount Crean, Lashly Mountains, Antarctica. Acanthodians are represented by scales of acritolepid Pechoralepis juozasi sp. nov., climatiid Nostolepis sp. cf. N. gaujensis Valiukevičius, diplacanthid Milesacanthus antarctica Young & Burrow, and an undetermined acanthodiform. The acanthodian assemblage resembles those from early Frasnian carbonates of central Iran. Chondrichthyan elements in the fauna include rare teeth of Aztecodus harmsenae Long & Young and Antarctilamna prisca Young, ctenacanthoid-type scales and branchial denticles which are possibly from Antarctilamna, and scales of an indeterminate chondrichthyan. An isolated set of acanthodid acanthodiform jaws from the uppermost ‘phyllolepid’ biozone of the Aztec Siltstone at Mount Ritchie, Warren Range, Antarctica is also described.
    Print ISSN: 0954-1020
    Electronic ISSN: 1365-2079
    Topics: Biology , Geography , Geosciences
    Published by Cambridge University Press
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 4
    facet.materialart.
    Unknown
    Relating microwave backscatter azimuth modulation to surface properties of the Greenland ice sheet (2006)
    Cambridge University Press
    Details
    Publication Date: 2006-01-01
    Description: Azimuth dependence of a normalized radar cross-section (σº) over the Greenland ice sheet is modeled with a simple surface scattering model. The model assumes that azimuth anisotropy in surface roughness at scales of 3–300 m is the primary mechanism driving the modulation. To evaluate the contribution of azimuth anisotropy in surface roughness to the radar backscatter, the model is compared to models based on isotropic surface roughness. The models are inverted to estimate snow surface properties using σº measurements from the C-band European Remote-sensing Satellite advanced microwave instrument in scatterometer mode. Results indicate that the largest mesoscale rms surface slopes are found in the lower portions of the dry snow zone. Estimates of the preferential direction in surface roughness are highly correlated with katabatic wind fields over Greenland, which is consistent with wind-formed sastrugi as the dominant mechanism causing azimuth modulation of σº. The maximum improvement of the azimuth modulation surface model compared to its isotropic counterparts occurs in the lower regions of the dry snow zone where the azimuth variability of σº is the largest. In regions with azimuth modulation over 1 dB, the mean root-mean-square error estimate of the azimuth-dependent surface scattering model is 0.46 dB compared with 0.70 dB for similar models using isotropic roughness.
    Print ISSN: 0022-1430
    Electronic ISSN: 1727-5652
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
  • 5
    facet.materialart.
    Unknown
    Calving and ice-shelf break-up processes investigated by proxy: Antarctic tabular iceberg evolution during northward drift (2008)
    Cambridge University Press
    Details
    Publication Date: 2008-01-01
    Description: Using a combination of satellite sensors, field measurements and satellite-uplinked in situ observing stations, we examine the evolution of several large icebergs drifting east of the Antarctic Peninsula towards South Georgia Island. Three styles of calving are observed during drift: ‘rift calvings’, ‘edge wasting’ and ‘rapid disintegration’. Rift calvings exploit large pre-existing fractures generated in the shelf environment and can occur at any stage of drift. Edge wasting is calving of the iceberg perimeter by numerous small edge-parallel, sliver-shaped icebergs, preserving the general shape of the main iceberg as it shrinks. This process is observed only in areas north of the sea-ice edge. Rapid disintegration, where numerous small calvings occur in rapid succession, is consistently associated with indications of surface melt saturation (surface lakes, firn-pit ponding). Freeboard measurements by ICESat indicate substantial increases in ice-thinning rates north of the sea-ice edge (from 30 m a−1), but surface densification is shown to be an important correction (〉2 m freeboard loss before the firn saturates). Edge wasting of icebergs in ‘warm’ surface water (sea-ice-free, 〉−1.8°C) implies a mechanism based on waterline erosion. Rapid disintegration (‘Larsen B-style’ break-up) is likely due to the effects of surface or saturated-firn water acting on pre-existing crevasses, or on wave- or tidally induced fractures. Changes in microwave backscatter of iceberg firn as icebergs drift into warmer climate and experience increased surface melt suggest a means of predicting when floating ice plates are evolving towards disintegration.
    Print ISSN: 0022-1430
    Electronic ISSN: 1727-5652
    Topics: Geography , Geosciences
    Published by Cambridge University Press on behalf of International Glaciological Society.
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER CURRENT
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...