Page 315 - Introduction to Paleobiology and The Fossil Record

302 INTRODUCTION TO PALEOBIOLOGY AND THE FOSSIL RECORD

Subphylum Order Key characteristics Stratigraphic
range

Linguliformea Lingulida Spatulate valves with pedicle usually Cambrian to
emerging between both shells Recent
Acrotretida Micromorphic forms with conical Cambrian to
ventral valve; dorsal valve with Devonian
platforms
Discinida Subcircular shells with conical ventral Ordovician to
valve and distinctive pedicle foramen Recent
Siphonotretida Subcircular, biconvex valves with spines Cambrian to
and elongate pedicle foramen Ordovician
Paterinida Strophic shells with variably developed Cambrian to
interareas Ordovician
Craniiformea Craniida Usually attached by ventral valve; dorsal Ordovician to
valve with quadripartite muscle scars Recent
Craniopsida Small oval valves with internal platforms Ordovician to
and marked concentric growth lines Carboniferous
Trimerellida Commonly gigantic, aragonitic shells, Ordovician to
with platforms and umbonal cavities Silurian
Rhynchonelliformea Chileida Strophic shells lacking articulatory Cambrian
structures but with umbonal
perforation
Dictyonellida Biconvex valves with large umbonal Ordovician to
opening commonly covered by a Permian
colleplax
Naukatida Biconvex shells with articulatory Cambrian
structures and apical foramen
Obolellida Oval valves with primitive articulatory Cambrian
structures
Kutorginida Strophic valves with interareas but Cambrian
lacking articulatory structures
Orthotetida Biconvex shells, commonly cemented, Ordovician to
with bilobed cardinal process Permian
Billingsellida Usually biconvex with transverse teeth Cambrian to
and simple cardinal process Ordovician
Strophomenida Concavoconvex, usually with a bilobed Ordovician to
cardinal process; recumbent life mode; Permian
cross-laminar shell structure with
pseudopunctae
Productida Concavoconvex valves with complex Ordovician to
cardinalia; recumbent or cemented life Triassic
mode; often with external spines
Protorthida Well-developed interareas, primitive Cambrian to
articulation and ventral free Devonian
spondylium
Orthida Biconvex, usually simple cardinal Cambrian to
process; pedunculate; delthyria and Permian
notothyria open
Pentamerida Biconvex, rostrate valves with cruralia Cambrian to
and spondylia variably developed Devonian
Rhynchonellida Usually biconvex, rostrate valves with Ordovician to
variably developed crurae Recent
Atrypida Biconvex valves with dorsally-directed Ordovician to
spiralia and variably developed jugum Devonian
Athyridida Usually biconvex valves with short hinge Ordovician to
line and posterolaterally-directed Jurassic
spiralia
Spiriferida Wide strophic valves with laterally- Ordovician to
directed spiralia; both punctate and Jurassic
impunctate taxa
Thecideida Small, strophic shells with complex Triassic to
spiralia including brachial ridges and Recent
median septum
Terebratulida Biconvex valves with variably developed Devonian to
long or short loops Recent