Sökning: "stem-group"

Visar resultat 1 - 5 av 8 avhandlingar innehållade ordet stem-group.

  1. 1. Exceptionally Preserved Cambrian Lophotrochozoa : Taxonomy, Systematics and Taphonomy of Chengjiang and Indian Springs Lophophorates

    Författare :Aodhán D. Butler; Michael Streng; Lars E. Holmer; Christian Skovsted; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Brachiopoda; Chengjiang; Lagerstätte; Cambrian Explosion; palaeobiology; stem-group; entoproct; phoronid; tommotiid; exceptional preservation.; Earth Science with specialization in Historical Geology and Palaeontology; Geovetenskap med inriktning mot historisk geologi och paleontologi;

    Sammanfattning : The origin and evolution of Lophotrochozoa can be traced to the plethora of lower Cambrian scleritome taxa.  We aim to determine the character suites linking these stem-Lophotrochozoa to their extant crown relatives, in particular the small shelly tommotiids and the stem-group brachiopods. LÄS MER

  3. 2. Decoding the fossil record of early lophophorates : Systematics and phylogeny of problematic Cambrian Lophotrochozoa

    Författare :Aodhán D. Butler; Michael Streng; Lars E. Holmer; Russell Garwood; Maggie Cusack; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Brachiopoda; Chengjiang; Lagerstätte; Cambrian Explosion; palaeobiology; stem-group; entoproct; phoronid; tommotiid; exceptional preservation; Earth Science with specialization in Historical Geology and Palaeontology; Geovetenskap med inriktning mot historisk geologi och paleontologi;

    Sammanfattning : The evolutionary origins of animal phyla are intimately linked with the Cambrian explosion, a period of radical ecological and evolutionary innovation that begins approximately 540 Mya and continues for some 20 million years, during which most major animal groups appear. Lophotrochozoa, a major group of protostome animals that includes molluscs, annelids and brachiopods, represent a significant component of the oldest known fossil records of biomineralised animals, as disclosed by the enigmatic ‘small shelly fossil’ faunas of the early Cambrian. LÄS MER

  4. 3. The evolution of the nuclear envelope

    Författare :Nadja Neumann; Anthony Poole; Gáspár Jékely; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Nuclear pore complex; bouquet; meiosis; nucleus; eukaryote evolution; nucleoporin; tree of life; stem group; recombination; Molecular biology; Molekylärbiologi; Molecular Biology; molekylärbiologi;

    Sammanfattning : The nucleus is one of the defining features of eukaryotes and the question of its origin is intimately linked to the evolution of the eukaryotic cell. It is delimited by a double lipid bilayer called the nuclear envelope, which separates the nuclear interior from the cytoplasm. LÄS MER

  5. 4. Early Cambrian Problematic Lophotrochozoans and Dilemmas of Scleritome Reconstructions

    Författare :Cecilia M Larsson; Lars E Holmer; Christian B Skovsted; Anette E S Högström; John S Peel; Glenn A Brock; Michael J Vendrasco; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Problematica; scleritome; Trachyplax; tommotiid; Cambrian; South Australia; North Greenland; Earth Science with specialization in Historical Geology and Palaeontology; Geovetenskap med inriktning mot historisk geologi och paleontologi;

    Sammanfattning : The emergence and radiation of metazoan body plans around the Precambrian/Cambrian boundary, some 500-600 million years ago, seems to be concordant with the appearance and diversification of preservable hard parts. Several Precambrian soft-bodied, multicellular organisms most likely represent stem-group bilaterians, but their fossil record is rather sparse. LÄS MER

  7. 5. The morphology and evolutionary significance of the anomalocaridids

    Författare :Allison Daley; Graham E. Budd; Nigel C. Hughes; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; anomalocaridids; Cambrian; Burgess Shale; exceptional preservation; palaeontology; Historical geology and palaeontology; Historisk geologi och paleontologi; Historical Geology and Paleontology; Historisk geologi och paleontologi;

    Sammanfattning : Approximately 600 to 500 million years ago, a major evolutionary radiation called the “Cambrian Explosion” gave rise to nearly all of the major animal phyla known today. This radiation is recorded by various fossil lagerstätten, such as the Burgess Shale in Canada, where soft-bodied animals are preserved in exquisite detail. LÄS MER