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Strophomenida (strophomenids; class Articulata) The largest order of brachiopods (Brachiopoda), now extinct, in which one valve is usually convex and the other flat or concave. There is a straight hinge line. The pedicle foramen is filled by one plate in each valve in adult shells, the pedicle having degenerated and been lost. Attachment is by cementation of the pedicle valve, with or without tubular spines from the valves. The shell structure is pseudopunctate. Strophomenida appeared in the Lower Ordovician and became extinct in the Lower Jurassic. The order includes the Carboniferous Productus giganteus (Gigantoproductus giganteus), the largest of all brachiopods.