A class of long-extinct marine invertebrates. Is a brachiopod hinge door with the key link. Hinge line straight, the base surface low. No carpal structure, with wrist marks, multi-plate without teeth. Hinge teeth, hinge fossa is not developed more. closed muscle scar evident, showing leaf-shaped, or dendritic. the main processes significantly, simple or complex. fake rash shell. shells decoration varied, both in the shell decorated with thorns. Late Ordovician beginning to emerge, to the Permian extinction.

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