ABSTRACT
The oldest brachiopods, the ‘inarticulates’, appeared in the Tommotian, arriving with a number of other skeletal invertebrates at about the same time. Their outlined geographic distribution depended strongly on regional sedimentary settings and climates. Cambrian Lingulata consisted mostly of ubiquitous taxa inhabiting silici-clastic and carbonate environments on the continental shelf and slope. Long-ranging Calciata dispersed to several paleo-continents and preferred shallow water carbonate, and mixed siliciclastic-carbonate shelves. Short-ranging Calciata were confined to a single paleocontinent. The first ‘articulates’ (nisusiids) appeared in the Atdabanian. From the Atdabanian onwards, two large realms, the ‘tropical’ and the ‘natal’, became differentiated with regard to brachiopod distribution, and were characterised by differing lingulate/calciate ratios, with greater diversity of calciates in the tropical realm.
