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An Early Cambrian organophosphatic brachiopod with calcitic granules
Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Palaeobiology.
2007 (English)In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 50, no 6, 1319-1325 p.Article in journal (Refereed) Published
Abstract [en]

The linguliform brachiopod Eoobolus from the Early Cambrian Mural Formation (Jasper National Park, Canadian Rocky Mountains) exhibits various calcitic features in its otherwise apatitic shell. It is argued here that the decomposition of the organic matter within the shell led to a microenvironment similar to those resulting in the phosphatization of soft tissues. This diagenetic regime encouraged the initial precipitation of apatite cements followed by calcite cements. By fully coating primary structures early apatite cements separate primary structures from the later precipitation of calcite cement. Round calcareous grains, about 3 µm in size, that occur in the centre of apatite botryoids must therefore represent original components of the shell. The equivalent pits of such calcareous granules are seen in the larval shells of many Palaeozoic linguliform brachiopods. This suggests that mixed organophosphatic-calcareous shells were relatively common at that time but that they have been overlooked owing to the obliteration of original calcareous structures by traditional acid preparation methods for the extraction of phosphatic fossils. The Eoobolus shell structure is intermediate between purely organophosphatic and calcitic shells. Although one such genus is not sufficient to reconstruct the ancestral composition of the brachiopod shell, it provides a means of recognizing other transitional forms that are needed to understand fully the shift in shell mineralogy.

Place, publisher, year, edition, pages
2007. Vol. 50, no 6, 1319-1325 p.
Keyword [en]
brachiopods, preservation, Cambrian, biomineralization
National Category
Earth and Related Environmental Sciences
URN: urn:nbn:se:uu:diva-11915DOI: 10.1111/j.1475-4983.2007.00729.xISI: 000251028400001OAI: oai:DiVA.org:uu-11915DiVA: diva2:39684
Available from: 2007-11-06 Created: 2007-11-06 Last updated: 2011-01-17Bibliographically approved

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