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Calcite and aragonite shell layers of the main classes of Molluscs are composed of monocrystalline units (prisms, tablets, laths or fibres). Scanning electron and atomic force microscopy studies show these units are composed of small round granules with a thin cortex (amorphous calcium carbonate and/or organic matrix). These granules are organo-mineral composites. A comparison of the size and shape of the granules in different taxa (Mollusca, Brachiopoda) suggests a possible relationship with taxonomy and/or phylogeny.
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Yannicke Dauphin (2008) studied this question.
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