1,721,275 research outputs found
Phylogenetic interpretations of macroevolution in deep-time
Full text linkThe fossil record yields information on macroevolutionary patterns that remains inaccessible from the study of extant organisms alone, presenting a natural laboratory for us to test hypotheses about the long-term drivers and processes of evolution. Fossil data are therefore increasingly incorporated into evolutionary analyses, both on their own and in combination with neontological data. Phylogeny (an explicit hypothesis of the evolutionary relationships between taxa) can be used as a framework to enable direct comparison of results of comparative methods across many different timescales and taxa, and is now commonly used in investigations of fossil data. This represents an important step towards a unified approach, however, it is not yet fully understood what the effect of using fossil data is on the results of downstream phylogenetic comparative methods, which were originally developed with only living taxa in mind. In this thesis I explore the validity of phylogenetic interpretations of fossil record data. I begin with only taxonomic classification and show that this can in some cases substitute for a cladistically inferred phylogeny in phylogenetic comparative methods, without biasing results. Moving on to scenarios where a timescaled phylogeny is available I investigate the relationship between phylogeny and extinction in the geological past, show that phylogenetic clustering of extinction was common in tetrapods, and present a summary of the ways in which fossil data biases this measurement. Finally, with timescaled phylogenies and a detailed continuous trait dataset available, I interrogate the fossil record of Sauropterygia to uncover the processes of evolutionary change in this highly labile clade. By comparing the results of a suite of phylogenetic comparative methods I demonstrate that neck length evolved through changing vertebral counts rather than somite growth; that the clade experienced a release in evolutionary constraint at the Triassic-Jurassic boundary; and that evidence does not support evolution towards a stationary adaptive peak as a suitable model for phenotypic change in the clade
Figure 11. Dorsal fin spines with trailing edge denticles, a in The characters of Palaeozoic jawed vertebrates
No full textFigure 11. Dorsal fin spines with trailing edge denticles, a potential synapomorphy of chondrichthyans. A, Brochoadmones milesi, UALVP 41495, an acanthodian. B, Tristychius arcuatus, NHMUK P.11378-79, a crown chondrichthyan and stem elasmobranch. Scale bars = 10 mm.Published as part of Brazeau, Martin D. & Friedman, Matt, 2014, The characters of Palaeozoic jawed vertebrates, pp. 779-821 in Zoological Journal of the Linnean Society 170 (4) on page 806, DOI: 10.1111/zoj.12111, http://zenodo.org/record/731265
The characters of Palaeozoic jawed vertebrates
No full textBrazeau, Martin D., Friedman, Matt (2014): The characters of Palaeozoic jawed vertebrates. Zoological Journal of the Linnean Society 170 (4): 779-821, DOI: 10.1111/zoj.12111, URL: http://dx.doi.org/10.1111/zoj.1211
Figure 10. Gnathostome dental anatomy. A in The characters of Palaeozoic jawed vertebrates
No full textFigure 10. Gnathostome dental anatomy. A, Torosteus pulchellus, NHMUK P.50966, an arthrodire placoderm. B, Ischnacanthus gracilis, NMS 1887.35.2, an acanthodian. C, Cladoselache sp., NHMUK P.9272, a crown gnathostome and chondrichthyan. D, Onychodus jandemarrai, NHMUK P.63576 (image reversed), a crown osteichthyan and sarcopterygian. Scale bars = 10 mm.Published as part of Brazeau, Martin D. & Friedman, Matt, 2014, The characters of Palaeozoic jawed vertebrates, pp. 779-821 in Zoological Journal of the Linnean Society 170 (4) on page 801, DOI: 10.1111/zoj.12111, http://zenodo.org/record/731265
Figure 5 in The characters of Palaeozoic jawed vertebrates
No full textFigure 5. Endoskeletal mineralization of gnathostomes. A, Buchanosteus confertituberculatus, NHMUK P.48675, an arthrodire placoderm. Fractured postorbital process/lateral commissure showing perichondral lining of canals, but absence of endochondral ossification. B, Griphognathus whitei, NHMUK P.52574, a crown osteichthyan and crown sarcopterygian. Ethmoid region showing perichondrally lined canals for olfactory tracts, surrounded by endochondral ossification. C, Tristychius arcuatus, NHMUK P.57305/6, a crown chondrichthyan and stem elasmobranch. Fragment of cranial skeleton showing prismatic calcified cartilage. D, Helodus simplex, NHMUK P.8212, a crown chondrichthyan and stem holocephalan. Basicranial region showing prismatic calcified cartilage. Scale bars = 5 mm.Published as part of Brazeau, Martin D. & Friedman, Matt, 2014, The characters of Palaeozoic jawed vertebrates, pp. 779-821 in Zoological Journal of the Linnean Society 170 (4) on page 792, DOI: 10.1111/zoj.12111, http://zenodo.org/record/731265
Trigonotarbus Pocock 1911
No full textTRIGONOTARBUS POCOCK, 1911 Type species Trigonotarbus johnsoni Pocock, 1911, by original designation. Included species Trigonotarbus arnoldi Petrunkevitch, 1955 b; Trigonotarbus stoermeri Schultka, 1991.Published as part of Jones, Fiona M., Dunlop, Jason A., Friedman, Matt & Garwood, Russell J., 2014, Trigonotarbus johnsoni Pocock, 1911, revealed by X-ray computed tomography, with a cladistic analysis of the extinct trigonotarbid arachnids, pp. 49-70 in Zoological Journal of the Linnean Society 172 (1) on page 56, DOI: 10.1111/zoj.12167, http://zenodo.org/record/531364
Figure 2 in Trigonotarbus johnsoni Pocock, 1911, revealed by X-ray computed tomography, with a cladistic analysis of the extinct trigonotarbid arachnids
No full textFigure 2. Hand specimens of Trigonotarbus johnsoni from the NHMUK collections. Scale bars = 1 mm.Published as part of Jones, Fiona M., Dunlop, Jason A., Friedman, Matt & Garwood, Russell J., 2014, Trigonotarbus johnsoni Pocock, 1911, revealed by X-ray computed tomography, with a cladistic analysis of the extinct trigonotarbid arachnids, pp. 49-70 in Zoological Journal of the Linnean Society 172 (1) on page 55, DOI: 10.1111/zoj.12167, http://zenodo.org/record/531364
Figure 6 in Early fossils illuminate character evolution and interrelationships of Lampridiformes (Teleostei, Acanthomorpha)
No full textFigure 6. Strict consensus of the 12 most parsimonious trees obtained after analysis 2 (with all 24 taxa, fossil and extant, included). Fossil taxa are indicated by daggers (†). Numbers above branches are Bremer indexes; tree length = 155 steps; consistency index, CI = 0.48; retention index, RI = 0.72.Published as part of Davesne, Donald, Friedman, Matt, Barriel, Véronique, Lecointre, Guillaume, Janvier, Philippe, Gallut, Cyril & Otero, Olga, 2014, Early fossils illuminate character evolution and interrelationships of Lampridiformes (Teleostei, Acanthomorpha), pp. 475-498 in Zoological Journal of the Linnean Society 172 (2) on page 489, DOI: 10.1111/zoj.12166, http://zenodo.org/record/531330
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
- …
