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Ontogeny, Intraspecific Variation, and Systematics of the Late Cambrian Trilobite <I>Dikelocephalus</I>

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dc.contributor.author Hughes, Nigel C. en
dc.date.accessioned 2012-10-24T13:47:37Z
dc.date.available 2012-10-24T13:47:37Z
dc.date.issued 1994
dc.identifier.citation Hughes, Nigel C. 1994. "<a href="http%3A%2F%2Fdx.doi.org%2F10.5479%2Fsi.00810266.79.1">Ontogeny, Intraspecific Variation, and Systematics of the Late Cambrian Trilobite Dikelocephalus</a>." <em>Smithsonian Contributions to Paleobiology</em>. 1&ndash;89. <a href="https://doi.org/10.5479/si.00810266.79.1">https://doi.org/10.5479/si.00810266.79.1</a> en
dc.identifier.issn 0081-0266
dc.identifier.uri http://hdl.handle.net/10088/19148
dc.identifier.uri http://dx.doi.org/10.5479/si.00810266.79.1
dc.description.abstract Biometric analyses of well-localized specimens of the trilobite <I>Dikelocephalus</I> from the St. Lawrence Formation (Upper Cambrian), northern Mississippi Valley, suggest that all specimens belong to a single, highly variable morphospecies, <I>D. minnesotensis</I>. A complex pattern of ontogenetically-related and ontogeny-independent variation produced a mosaic of morphotypes, which show greater diversity than previously recorded within trilobite species. There is considerable variation within collections made from single beds. Variations of characters among collections are mosaic, and are clinal in some cases. Patterns of variation within <I>Dikelocephalus</I> cannot be related to lithofacies occurrence. There are no obvious temporal variations in <I>D. minnesotensis</I> within the St. Lawrence Formation, but some <I>Dikelocephalus</I> from the underlying Tunnel City Group may belong to a different taxon. The validity of this early taxon is questionable due to a lack of available material. The mosaic pattern of variation in <I>Dikelocephalus</I> mimics that documented at higher taxonomic levels in primitive libristomate trilobites, and helps explain difficulties in providing a workable taxonomy of primitive trilobites. Results caution proposition of evolutionary scenarios that do not take account of intraspecific variation. The recovery of dorsal shields of <I>Dikelocephalus</I> permits the first detailed reconstruction of the entire exoskeleton. The systematics of the genus is revised and twenty-five species are suppressed as junior synonyms of <I>D. minnesotensis</I>. en
dc.relation.ispartof Smithsonian Contributions to Paleobiology en
dc.title Ontogeny, Intraspecific Variation, and Systematics of the Late Cambrian Trilobite <I>Dikelocephalus</I> en
dc.type Journal Article en
dc.identifier.srbnumber 113499
dc.identifier.doi 10.5479/si.00810266.79.1
rft.jtitle Smithsonian Contributions to Paleobiology
rft.issue 79
rft.spage 1
rft.epage 89
dc.description.SIUnit SISP en
dc.citation.spage 1
dc.citation.epage 89
dc.relation.url http://dx.doi.org/10.5479/si.00810266.79.1

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