Cryptodonta

bivalve subclass

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June 25, 2026

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The Cryptodonta are a subclass of bivalves, a type of marine mollusk. They are characterized by a hinge that is either weakly toothed or lacks teeth entirely. A distinctive feature of their shell structure is the presence of simple prisms made of aragonite, with nacre on the inside. Cryptodonts possess large posterior protobranch gills and small labial palps. This group is considered to be of ancient lineage and lives in marine environments, typically burrowing in sediment. The order Solemyoida is part of this subclass and includes species with elongated shells that lack hinge teeth and may host symbiotic sulfur-oxidizing bacteria in their gills.1

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bivalve
Annotated classification
Subclass Cryptodonta Hinge either weakly taxodont or edentulous; distinctive shell structure of aragonitic simple prisms and nacre internally; large posterior protobranch ctenidia; small labial palps; of primitive and ancient lineage; marine; unattached; infaunal. Order Solemyoida Shell valves equal and elongate, lacking hinge teeth, covered by a…
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Subclass Cryptodonta Hinge either weakly taxodont or edentulous; distinctive shell structure of aragonitic simple prisms and nacre internally; large posterior protobranch ctenidia; small labial palps; of primitive and ancient lineage; marine; unattached; infaunal. Order Solemyoida Shell valves equal and elongate, lacking hinge teeth, covered by a…
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