FOSSIL INVERTEBRATES/Brachiopods 305 Figure Range of brachiopod morphologies: (A) Pseudolingula (Ordovician lingulide: Â2); (B) Nushbiella (Ordovician siphonotretide: Â10); (C) Crania (Palaeogene craniide: Â2.5); (D) Sulevorthis (Ordovician orthide: Â3); (E) Rafinesquina (Ordovician strophomenide: Â1/3); (F) Grandaurispina (Permian productide: Â1); (G, H) Rostricellula (Ordovician rhynchonellide: Â3); (I) Cyclacantharia (Permian richthofeniid: Â0.5); (J) Neospirifer (Permian spiriferide: Â2/3); (K,L) Seymourella (Palaeogene terebratulide: Â1) Throughout the Phanerozoic, the brachiopods have participated in a spectrum of level-bottom, benthic palaeocommunities Pioneer studies on Silurian brachiopods suggested that their palaeocommunities were depth related (Figure 8A) The onshore–offshore assemblages of the Lingula, Eocoelia, Pentamerus, Stricklandia, and Clorinda palaeocommunities have been amplified and modified to form the basis of Benthic Assemblage (BA) zones 1–5, ranging from intertidal environments to the edge of the continental slope; more basinal environments are included in an extra BA Parallel studies on Mesozoic brachiopods have, on the other hand, suggested that brachiopoddominated palaeocommunities were controlled by substrate rather than depth (Figure 8B) Clearly, a combination of these and other factors in reality controlled the distributions of the Brachiopoda in a complex system of suspension-feeding guilds Brachiopods have also acted as substrates for a variety of small epifaunal animals The progressive and sequential colonization of Devonian spiriferids by Spirorbis, Hederella, Paleschara, and Aulopora marks the development of sere and climax palaeocommunities on a brachiopod shell It has been suggested that such animals congregated adjacent to the inhalant currents on the median parts of the anterior commissure An alternative hypothesis reverses the direction of flow through the brachiopod mantle cavity, and thus these commensal organisms took advantage of waste being ejected from the brachiopod Geographical Distribution The biogeographical patterns of the linguliformean brachiopods were quite different from those of the craniiformeans and rhynchonelliformeans The former had planktotrophic larval phases with a facility for wide dispersal; in contrast, the lecithotrophic larvae of the latter were short-lived Brachiopods dominated the benthos of the Palaeozoic evolutionary fauna Nevertheless, Cambrian brachiopods were organized into tropical and natal realms, where linguliformeans developed widespread distributions in shelf and slope settings, and rhynchonelliformeans were more diverse in the tropics, preferring shallow-water carbonate and mixed carbonate– siliciclastic environments Ordovician brachiopods generally showed a decreased provincialism during