Lower Cambrian, Middle Cambrian, Ordovician – Holocene
Craniata is an extinct class of stationary, epifaunal suspension feeders.
Characteristics of the Class
- Calcitic or Aragonitic
- Free lying or encrusting
- Laminar (tabular) secondary layers
- Normally pinnate and containing gonads
Treatise on Invertebrate Paleontology, Part H, Vol. 2 (2000):
- Brachiopods with calcitc or possibly aragonitic inarticulated shells with laminar (tabular) secondary layers; posterior body wall complete, inner mantle lobes not developed at valve margins, pedicle not developed, shell free lying or with encrusting ventral valve cemented by larval epithelium; muscle system with a single pair of internal oblique and with paired outside lateral muscles attached anteriorly to the body wall; alimentary tract more or less axial with anus medially on posterior body wall; lophophore initially with median tentacle lost during growth, tentacles in double row in postrocholophous growth stages only; nervous system in base of epidermis with paired subenteric ganglia; mantle canal systems with vascula terminalia peripheral only, normally pinnate, containing gonads; larva lecithotrophic without shell.