Calcification in the bivalve periostracum |
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Authors: | JOSEPH G. CARTER ROBERT C. ALLER |
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Affiliation: | Department of Geology, Colgute University, Hamilton, New York 13346. U.S.A;Department of Geology and Geophysics, Yale University. New Haven, Connecticut 06520, U.S.A. |
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Abstract: | The periostracum in certain bivalves is imbedded with calcified, spiculelike structures analogous if not homologous to cuticular spicules found in the Aplacophora and Polyplacophora (chitons). Although rare or absent in most living bivalves, calcified periostracal structures are apparently an ancestral feature in some bivalve groups, i.e. the Mytilacea, Permophoridae, Myoida. and Anomalodesmata. Ancestors of the Bivalvia and Polyplacophora may have been covered with a flexible, spiculestudded cuticle. Shell plates in these two classes may have originated through a modification of the mechanism of spiculelike cuticular calcification. resulting in a primordial shell with simple prismatic structure. |
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