| Deep molluscan phylogeny: synthesis of palaeontological and neontological data. | |
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MedLine Citation:
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PMID: 17652065 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The position of the earliest-derived living molluscs, the Polyplacophora (chitons) and shell-less vermiform Aplacophora, remains highly contentious despite many morphological, developmental and molecular studies of extant organisms. These two groups are thought to represent either a basal molluscan grade or a clade (Aculifera) sister to the 'higher' molluscs (Conchifera). These incompatible hypotheses result in very different predictions about the earliest molluscs. A new cladistic analysis incorporating both Palaeozoic and extant molluscs is presented here. Our results support the monophyly of Aculifera and suggest that extant aplacophorans and polyplacophorans both derive from a disparate group of multivalved molluscs in two major clades. Reanalysis of the critical Ordovician taxon 'Helminthochiton' thraivensis shows that this animal lacks a true foot despite bearing polyplacophoran-like valves. Its position within our phylogenetic reconstruction indicates that many fossil 'polyplacophorans' in the order Palaeoloricata are likely to represent footless stem-group aplacophorans. 'H.' thraivensis and similar forms such as Acaenoplax may be morphological stepping stones between chitons and the shell-less aplacophorans. Our results imply that crown-group molluscan synapomorphies include serial repetition, the presence of a foot, a mineralized scleritome and a creeping rather than worm-like mode of life. |
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Authors:
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Julia D Sigwart; Mark D Sutton |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Proceedings. Biological sciences / The Royal Society Volume: 274 ISSN: 0962-8452 ISO Abbreviation: Proc. Biol. Sci. Publication Date: 2007 Oct |
Date Detail:
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Created Date: 2007-10-04 Completed Date: 2007-11-13 Revised Date: 2009-11-18 |
Medline Journal Info:
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Nlm Unique ID: 101245157 Medline TA: Proc Biol Sci Country: England |
Other Details:
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Languages: eng Pagination: 2413-9 Citation Subset: IM |
Affiliation:
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National Museum of Ireland - Natural History, Merrion Street, Dublin 2, Ireland. julia.sigwart@ucd.ie |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animals Fossils Mollusca / anatomy & histology, classification* Phylogeny* |
| Comments/Corrections | |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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