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The Early Cambrian (Botomian) stem group brachiopod Mickwitzia from Northeast Greenland
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
2003 (English)In: Acta Palaeontologica Polonica, ISSN 0567-7920, E-ISSN 1732-2421, Vol. 48, no 1, 1-20 p.Article in journal (Refereed) Published
Abstract [en]

The problematic brachiopod Mickwitzia Schmidt, 1888 is re-described based on new material of M. cf. occidens Walcott, 1908 from the Early Cambrian (Botomian) Bastion and Ella Island formations of Northeast Greenland. Etched material demonstrates that Mickwitzia has a lingulid-like juvenile ("larval") shell with trails of nick-points, reflecting the movement of marginal setae. Juvenile and early mature ventral valves have a lingulid-like pseudointerarea with a pedicle groove. The shell of M. cf. occidens is only partially phosphatic, in particular around the juvenile-early mature shell in both valves. The phosphatic shell includes at least two types of cylindrical structures: (1) slender columns identical with the columns of acrotretoid brachiopods and (2) relatively thicker tubes which may be open to the exterior surface and have internal striations (on the ventral pseudointerarea). The striations are most likely imprints of microvilli and these tubes can be inferred to have contained setae. The thinner linguliform columns and thicker setigerous striated tubes are considered to be homologous with identical structures in the sellate and mitral sclerites of the problematic Micrina, which has been identified as a probable primitive stem group of the Brachiopoda. Mickwitzia represents a more derived member of the stem group Brachiopoda.

Place, publisher, year, edition, pages
2003. Vol. 48, no 1, 1-20 p.
Keyword [en]
Brachiopoda, Mickwitzia, ontogeny, shell structure, Cambrian, Botomian, Greenland
National Category
Earth and Related Environmental Sciences
Identifiers
URN: urn:nbn:se:uu:diva-91214OAI: oai:DiVA.org:uu-91214DiVA: diva2:163871
Available from: 2003-12-15 Created: 2003-12-15 Last updated: 2013-05-01Bibliographically approved
In thesis
1. The Early Cambrian Fauna of North-East Greenland
Open this publication in new window or tab >>The Early Cambrian Fauna of North-East Greenland
2003 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Den tidigkambriska faunan från Nordöstgrönland
Abstract [en]

Small shelly fossils are common in sediments of Early Cambrian age and include the earliest common representatives of metazoan animals with mineralized hard parts. The group includes fossils of very different morphology, composition and ultrastructure. They seem to represent skeletal remains of numerous animal groups, the biological affinities of which are largely unresolved. However, the wide geographic range of many forms has the potential to enhance biostratigraphic and palaeogeographic resolution in the Early Cambrian.

The late Early Cambrian sequence of North-East Greenland has yielded an assemblage of more than 88 species of small shelly fossils, brachiopods and trilobites, indicative of a middle Dyeran age (Botoman equivalent). The recovered fossils include a number of species that are known from other Early Cambrian palaeocontinents, and particularly strong ties to late Early Cambrian faunas of Australia are documented. The many cosmopolitan taxa thus identified suggests a close juxtaposition of palaeocontinents at this time.

The systematic affinity of many of these small shelly fossils is poorly understood, partly because of their fragmentary nature and poor preservation. However, new data from North-East Greenland improves our understanding of the function and biological affinity of certain taxa. Collections of the problematic fossil Mongolitubulus from North and North-East Greenland exhibit characters indicative of a defensive function as spines of bivalved arthropods, while species of the problematic genus Triplicatella represent the opercula of an unknown tubular shell, probably related to orthothecid hyoliths. The bivalved fossil Mickwitzia from North-East Greenland combines characters of linguliform brachiopods and sclerites of Micrina, a non-bivalved problematic form (halkieriid) from Australia. The combination suggests that Mickwitzia is a stem group brachiopod and strengthens arguments for a halkieriid ancestry of the brachiopod phylum.

Place, publisher, year, edition, pages
Uppsala: Institutionen för geovetenskaper, 2003. 22 p.
Keyword
Earth sciences, Early Cambrian, Dyeran, Botoman, Biostratigraphy, Palaeogeography, Small Shelly Fossils, Brachiopoda, Mollusca, Hyolitha, Trilobita, Geovetenskap
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:uu:diva-3910 (URN)91-506-1731-1 (ISBN)
Public defence
2004-01-16, Föreläsningssalen, Paleontologiska museet, Norbyvägen 22, Uppsala, 13:00
Opponent
Supervisors
Available from: 2003-12-15 Created: 2003-12-15Bibliographically approved

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Skovsted, Christian B.Holmer, Lars E.

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