1,721,001 research outputs found
Rare earth element systematics of fossil bone revealed by LA-ICPMS analysis
No full textIntra-bone rare earth element (REE) fractionation trends were studied by LA-ICPMS analysis to put constraints on (1) the mechanisms controlling REE fractionation within fossil bones; (2) the relative timing of REE uptake in various parts of fossil bone and (3) the origin of REE in fossil bones. We have evaluated REE bone profiles across 54 fossil bones from a broad range of well-characterised taphonomic settings ranging in age from Triassic to early Medieval. REE patterns and concentration gradients are highly variable and intra-bone fractionation trends in (La/Yb)(N) vs. (La/Sm)(N) space of few specimens cover almost the entire range previously observed for bulk samples. Intra-bone variability of Ce anomalies, as well as variable Y/Ho and (La/La ) N is also observed. Sometimes, diagenetic fluids with fractionated, HREE enriched compositions have entered the bone from the marrow cavity, producing secondary REE uptake profiles. Theoretical intra-bone fractionation trends, modelled using lattice strain theory, concur with most REE data but some trends cannot be modelled using realistic boundary conditions. This fact, as well as the occurence of positive and negative Ce anomalies within the same fossil sample, hint towards changing REE compositions of diagenetic fluids over the timescales of REE uptake. Because apparent Ce anomalies frequently evolve over bone profiles and Ce anomalies can be inherited from previous fractionation events, Ce anomalies are a highly ambiguous tracer for constraining ambient redox conditions. In general, bioapatite REE signatures may not always reliably reflect ambient taphonomic or redox conditions and diagenetic fluid compositions. Therefore REE patterns and Ce anomalies of fossil bones must be interpreted cautiously as they vary spatially within skeletal remains and are affected by intra-bone fractionation processes as well as changing compositions of the diagenetic fluid. (C) 2012 Elsevier Ltd. All rights reserved.German National Science Foundation (DFG) [TU 148/2-1
Figure 1 in A new species of Cymbospondylus (Diapsida, Ichthyosauria) from the Middle Triassic of Nevada and a re-evaluation of the skull osteology of the genus
No full textFigure 1. Holotype of Cymbospondylus nichollsi sp. nov., specimen FMNH PR2251 in lateral (A), dorsal (B) and ventral (C) view. C shows the upper surface of the specimen as found in the field. Note the sharp bend in the cervical vertebral column. Scale bar = 20 cm.Published as part of <i>Fröbisch, Nadia B., Sander, P. Martin & Rieppel, Olivier, 2006, A new species of Cymbospondylus (Diapsida, Ichthyosauria) from the Middle Triassic of Nevada and a re-evaluation of the skull osteology of the genus, pp. 515-538 in Zoological Journal of the Linnean Society 147 (4)</i> on page 518, DOI: 10.1111/j.1096-3642.2006.00225.x, <a href="http://zenodo.org/record/10114562">http://zenodo.org/record/10114562</a>
Figure 12 in A new species of Cymbospondylus (Diapsida, Ichthyosauria) from the Middle Triassic of Nevada and a re-evaluation of the skull osteology of the genus
No full textFigure 12. Strict consensus of three most parsimonious trees reflecting the hypothesized phylogenetic relationships of Cymbospondylus nichollsi sp. nov. to a selection of mainly Triassic ichthyosaurs. Based on the data matrix of Nicholls & Manabe (2001). After inclusion of C. nichollsi, 15 taxa and 44 characters were considered in the analysis.Published as part of <i>Fröbisch, Nadia B., Sander, P. Martin & Rieppel, Olivier, 2006, A new species of Cymbospondylus (Diapsida, Ichthyosauria) from the Middle Triassic of Nevada and a re-evaluation of the skull osteology of the genus, pp. 515-538 in Zoological Journal of the Linnean Society 147 (4)</i> on page 535, DOI: 10.1111/j.1096-3642.2006.00225.x, <a href="http://zenodo.org/record/10114562">http://zenodo.org/record/10114562</a>
Cymbospondylus Leidy 1868
No full textCymbospondylus Leidy, 1868 (14) Type species Cymbospondylus piscosus Leidy, 1868 (14) Referred species Cymbospondylus petrinus Leidy, 1868 (14); Cymbospondylus buchseri (15); Cymbospondylus nichollsi (16); *Corresponding author. Email: [email protected] (P.M.S.); [email protected] (E.M.G.); [email protected] (L.S.) Cymbospondylus duelferi (17); Cymbospondylus youngorum sp. nov. Genus diagnosis For a recent detailed diagnosis of the genus, see (17). In addition, the results of the phylogenetic analysis in this study offer an apomorphy-based diagnosis.Published as part of Sander, P. Martin, Griebeler, Eva Maria, Klein, Nicole, Juarbe, Jorge Velez, Wintrich, Tanja, Revell, Liam J. & Schmitz, Lars, 2021, Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans, pp. 1-15 in Science (New York, N. Y.) (New York, N. Y.) 374 (6575) on pages 1-2, DOI: 10.1126/science.abf5787, http://zenodo.org/record/580532
A new species of Cymbospondylus (Diapsida, Ichthyosauria) from the Middle Triassic of Nevada and a re-evaluation of the skull osteology of the genus
No full textFigure 6. Drawing of the skull of Cymbospondylus nichollsi sp. nov. (FMNH PR2251) in ventral view. See Appendix for explanation of abbreviations. Scale bar = 10 cm.Published as part of Fröbisch, Nadia B., Sander, P. Martin & Rieppel, Olivier, 2006, A new species of Cymbospondylus (Diapsida, Ichthyosauria) from the Middle Triassic of Nevada and a re-evaluation of the skull osteology of the genus, pp. 515-538 in Zoological Journal of the Linnean Society 147 (4) on page 526, DOI: 10.1111/j.1096-3642.2006.00225.x, http://zenodo.org/record/463473
Fig. 6 in Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans
No full textFig. 6. The adaptive landscape of body-size evolution. (A and B) Ichthyosaurs (A) feature two early adaptive shifts toward larger skull length, whereas cetaceans (B) entered selective regimes that promoted larger skull width much later in their evolution.Published as part of Sander, P. Martin, Griebeler, Eva Maria, Klein, Nicole, Juarbe, Jorge Velez, Wintrich, Tanja, Revell, Liam J. & Schmitz, Lars, 2021, Early giant reveals faster evolution of large body size in ichthyosaurs than in cetaceans, pp. 1-15 in Science (New York, N.Y.) 374 (6575) on page 6, DOI: 10.1126/science.abf5787, http://zenodo.org/record/580532
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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