Phylum Brachiopoda

Class Inarticulata (to go to Articulata, click here.)
Values chitinophosphatic or calcareous
periostracum respectively chitino-proteinaceous or proteinaceous
punctate or impunctate
articulation absent to rare
muscles and body wall hold shells together
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attachment by pedicle (lingulids)
cementation of pedicle value to substrate (craniaceans)
no attachment (Trimerella)
L. Cambrian - Holocene

Order Lingulida
  Biconvex, often large (4-5cm)
  beak generally terminal in both valves
  pedicle, where present, emerging posteriorly between valves
  L. Cambrian - Holocene
  Lingula, Trimerella

Order Acrotretida
  outline circular-subcircular, very small (many less than 2mm)
  shell phosphatic or calcareous (punctate)
  pedicle confined to pedicle valve, if present
  beak marginal
  L. Cambrian - Holocene
  Acrotreta, Orbiculoidea, Crania

Order Obolellida
  calcareous shell
  biconvex, small (3-4mm)
  subcircular-elongate oval
  well defined pseudointerarea
  pedicle emergent site variable
  marginal beak (brachial valve)
  L. -  M. Cambrian
  Bicia

Order Paterinida
  phosphatic shell
  rounded or elliptical, smaller than 5mm
  pedical valve convex to hemiconical
  triangular delthyrium divides pseudointerarea
  homeochilidium partially closes notothyrium
  L. Cambrian - M. Ordovician
  Micromitra, Paterina


Class Articulata