304 FOSSIL INVERTEBRATES/Brachiopods Table The Linguliformea, Craniiformea, and Rhynchonelliformea Subphylum Order Key characteristics Stratigraphical range Linguliformea Lingulida Spatulate valves with pedicle usually emerging between both shells Micromorphic forms with conical ventral valve; dorsal valve with platforms Subcircular shells with conical ventral valve and distinctive pedicle foramen Subcircular, biconvex valves with spines and elongate pedicle foramen Strophic shells with variably developed interareas Cambrian Recent Acrotretida Discinida Siphonotretida Paterinida Craniiformea Craniida Craniopsida Trimerellida Rhynchonelliformea Chileida Dictyonellida Naukatida Obolellida Kutorginida Orthotetida Billingsellida Strophomenida Productida Protorthida Orthida Pentamerida Rhynchonellida Atrypida Athyridida Spiriferida Thecideida Terebratulida Usually attached by ventral valve; dorsal valve with quadripartite muscle scars Small oval valves with internal platforms and marked concentric growth lines Commonly gigantic, aragonitic shells, with platforms and umbonal cavities Strophic shells lacking articulatory structures but with umbonal perforation Biconvex valves with large umbonal opening commonly covered by a colleplax Biconvex shells with articulatory structures and apical foramen Oval valves with primitive articulatory structures Strophic valves with interareas but lacking articulatory structures Biconvex shells, commonly cemented, with bilobed cardinal process Usually biconvex with transverse teeth and simple cardinal process Concavoconvex, usually bilobed cardinal process; recumbent life mode; cross laminar shell structure with pseudopunctae Concavoconvex valves with complex cardinalia; recumbent or cemented life mode; often with external spines Well developed interareas, primitive articulation and ventral free spondylium Biconvex, usually simple cardinal process; pedunculate; delthyria and notothyria open Biconvex, rostrate valves with cruralia and spondylia variably developed Usually biconvex, rostrate valves with variably developed crurae Biconvex valves with dorsally directed spiralia and variably developed jugum Usually biconvex valves with short hingeline and posterolaterally directed spiralia Wide strophic valves with laterally directed spiralia; both punctate and impunctate taxa Small, strophic shells with complex spiralia including brachial ridges and median septum Biconvex valves with variably developed long or short loops evolved clasping spines and possibly extended mantle fibres to help stabilize their shells In a number of groups, the pedicle atrophied during ontogeny Many taxa thus developed strategies involving inverted, pseudoinfaunal, and recumbent life modes; Cambrian Devonian Ordovician Recent Cambrian Ordovician Cambrian Ordovician Ordovician Recent Ordovician Carboniferous Ordovician Silurian Cambrian Ordovician Permian Cambrian Cambrian Cambrian Ordovician Permian Cambrian Ordovician Ordovician Permian Ordovician Triassic Cambrian Devonian Cambrian Permian Cambrian Devonian Ordovician Recent Ordovician Devonian Ordovician Jurassic Ordovician Jurassic Triassic Recent Devonian Recent a number lived in cosupportive clusters and others mimicked corals Not all brachiopods were sessile; a few, such as Lingula, adopted an infaunal life style, whereas the articulated forms, Camerisma and Magadina, were semi-infaunal