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Family Spondylidae - thorny oysters
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Class |
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Bivalvia |
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No. of Genera in Ref. |
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No. of Species in Ref. |
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Environment |
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Fresh : No |
Brackish : No |
Marine : Yes |
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First Fossil Record |
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Remark |
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Shell stout, highly variable in shape but generally subequilateral, rounded and higher than long; usually inequivalve and cemented to substrate by the right (lower) valve, which is then higher and more convex than the left (upper) valve. Hinge line straight, with a small, more or less equal ear on either side of the median, orthogyrate umbo. Outer surface with more or less spinose to scaly irregular radial ribs, often brightly coloured (at least at the left valve). Umbones on top of a trigonal cardinal area, which is usually higher in the right valve than in the left valve. Ligament mainly internal, lodged in a deep median pit of the hinge plate. Hinge stout, with 2 strong curved teeth and 2 deep sockets in each valve, symmetrically arranged in relation to the internal ligament. Interior of shell porcelaneous. A single, rounded (posterior) adductor muscle scar. Pallial line without a sinus. Gills of filibranchiate type, with foldd branchial sheets. Foot reduced, without a byssus in the adult. Siphons absent. Mantle widely open, with marginal tentacles and eyes. Sedentary animals, living mainly in relatively shallow waters in coralline areas, generally strongly cemented to hard substrates by their right valve. Suspension filter-feeders. Sexes separate, or hermaphrodites. Free swimming larval stage present. A temporary, postlarval attachment by means of a byssus occurs before the cementation to the substrate by the right valve. Locally collected for food in some areas, Spondylidae are nowadays mainly exploited for their shell which is used as a source of lime or in shellcraft (Ref. 348). |
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