ABSTRACT
Over the past 30 years a variety of methods have been used to characterise benthic marine communities for comparison with others surrounding them in both space and time. However, because individual brachiopods do not interact with each other, the individual species distribution is a more ecologically natural unit than their grouping together as ‘communities’. Nevertheless, the groupings of these species as communities form a recognisable and identifiable series of entities which justifies their formal recognition and naming. From the Cambrian to the Devonian there was a steady spread of brachiopod colonisation from relatively shallow water (BA2) in level-bottom marine communities both shorewards (to BA1) and progressively off-shore (to BA7) so that assemblages thrived from perhaps intertidal to the deeper shelf and slope. A brief summary is presented of key works; there is little published on Cambrian brachiopod-dominated assemblages, but in the early Ordovician there was considerable endemism, which reduced as time went by and the more substantial continents drew closer. By the early Silurian most of the level-bottom faunas were relatively cosmopolitan, apart from those developed in high latitudes, but by the end of the Silurian more endemism had again developed. The absolute depth of each community varied depending on water clarity and other factors but for each benthic assemblage zone was approximately constant as the individual communities replaced each other laterally and over geological time.
