SUMMARY The status, origins and relationships of the various groups of Palaeozoic corals are reviewed. Five orders are currently recognized: Rugosa, Tabulata, Heterocorallia, Cothoniida and Kilbuchophyllida, to which I add the Tabulaconida and Numidiaphyllida. The Rugosa and Tabulata are considered to be broadly monophyletic clades, and the Tabulata are confirmed as zoantharian corals. Morphological features, particularly aspects of septal insertion in both groups, are discussed as clues to their likely origins and relationships. They are not considered to have had a skeletonized common ancestor, but they may have arisen as separate skeletonization events from the same broad group of anemones, represented by the living Zoanthiniaria. The Rugosa are not considered to be ancestral to the Scleractinia. The latter, together with the Permian Numidiaphyllida, are considered to have evolved through skeletonization events among a group of anemones derived from the Actiniaria/Corallimorpharia, a member of which also gave rise to the Kilbuchophyllida in the Ordovician. The pattern of septal insertion in the Heterocorallia is controversial and the relationship of these corals to contemporary coral groups remains uncertain. The increasingly important record of Cambrian coralomorphs is assessed, and considered to include several genera of zoantharian corals. However, although similarities are apparent, none is regarded as directly ancestral to the post-Cambrian coral clades. The history of diversification and extinction of corals through the Palaeozoic is briefly reviewed.

SUMMARY Palaeozoic coral faunas were dominated by two orders of Zoantharian corals, the Rugosa and the Tabulata. Almost all rugose and tabulate corals developed an epitheca or holotheca around the corallum and possessed small to minute attachment scars. A limited number had an encrusting life style and many others could facultatively encrust to some extent when settling by chance on a hard substrate. However, most were effectively free living on a soft substrate as mature coralla. A high percentage of rugose corals were solitary and of the colonial genera, few exhibited physical integration of modules within the colony. In contrast, most of the exclusively modular tabulate corals possessed some degree of integration. Colony formation in tabulate corals was, with doubtful exceptions, solely by non-parricidal increase, whereas both non-parricidal and parricidal increase, the latter in a minor role, occur in the Rugosa. The sources of variation in solitary and colonial Palaeozoic corals are reviewed and data on growth rates, measured on the basis of cyclomorphic variation expressed as density band couplets, are assessed. Growth-form variation in solitary corals and its relationship to stability on the substrate are explored. Growth strategies in colonial corals are described and their adaptive success under different environmental conditions is discussed. Colonial growth-forms were a function of the interaction between growth strategy and prevailing conditions during astogeny, although some species had genetically constrained, relatively invariate growth-forms. Factors controlling the distribution of Palaeozoic corals in the environment–substrate and turbidity, water energy, depth, light, temperature and variations in salinity and oxygenation - are reviewed. Palaeozoic coral diversity was much lower than that of Recent hermatypic scleractinian corals in comparable environments. Most Palaeozoic corals were adapted to soft substrates in warm, shelf seas, and made a limited contribution to reef frameworks. It is concluded that none of them developed a symbiosis with algae in contrast to zooxanthellate scleractinian corals.

In recent years, our understanding of Palaeozoic corals has increased enormously. Several new groups have been discovered, extending the range of corals back to the early Cambrian, and we now have a clearer idea of the relationships between them. None of them was a direct ancestor to the post‐Palaeozoic corals. Similarly, the ecology of Palaeozoic corals differed from that of their living relatives in important respects. Palaeozoic corals were principally adapted for life on soft substrates and were not the spectacular reef‐builders that modern corals have become. However, their contribution to Palaeozoic ecosystems is nonetheless fascinating. Their structural adaptations and growth‐forms can tell us much about life and processes on Palaeozoic sea floors.

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Abstrart: Conodont and graptolite dating provide a high resolution biostratigraphical framework for correlation across the Southern Upland Fault. The establishment of an early Caradoc age for the red chert and volcanic sequences within the Northern Belt of the Southern Uplands confounds the accretionary prism model. and our data support the view that following the obduction of the Ballantrae ophiolite, fan complexes prograded southeastwards across a narrow, fault-bounded shelf into the deep basin of the Northern Belt. The fan complexes were initiated by uplift in the hinterland, caused by the intrusion of plutons into the Midland Valley Terrane. Sedimentation was controlled by regional extension, subsidence and eustasy through the Llanvirn and Caradoc. Basic lavas, with attenuated within-plate geochemical signatures, were erupted during the early Caradoc peak of extension and may have just post-dated the initiation of southwards subduction beneath the Lake District.