Settlement strategy in Symplectophyllum (Cnidaria, Rugosa)

1. IntroductionThe larger solitary corals of the Early Carboniferous in eastern Australia – Amygdalophyllum Dun & Benson, 1920, Merlewoodia Pickett, 1967 and Symplectophyllum Hill, 1934 – have broad dissepimentaria characterised by an outer zone of large and irregular lonsdaleoid dissepiments, axial of which is a zone of naotic dissepiments, with regular dissepiments only the innermost zone. By contrast, the septa of the inner part of the corallite are thickened and braced by tabulae and regular dissepiments, and the axial structure is robust (except in Merlewoodia). Specimens of these genera are usually recovered as decorticated individuals, having undergone some penecontemporaneous erosion. Because of the zone of lonsdaleoid dissepiments, the outer part of the corallite is fragile, and little erosion is needed for decortication. Occasionally however, notably at a locality on “Pinaroo Plain” station at Caroda, near Bingara, New South Wales, specimens of Symplectophyllum are commonly found in growth position within larger colonies of the tabulate genus Syringopora, the growth direction of the two species being subparallel. More rarely they may be associated with branching lithostrotionids such as Cionodendron Benson & Smith, 1923 or Pickettodendron Denayer & Webb, 2015. The dynamics of this association form the subject of this article.2. Localities and ageTwo localities are the principal sources of the present material. The first, which has provided the largest number of spec