The Permian coral Numidiaphyllum: New insights into anthozoan phylogeny and Triassic scleractinian origins

The Permian coral Numidiaphyllum, having an unusual septal arrangement and an aragonitic skeleton, has been classified in the Rugosa. The type species of Numidiaphyllum shows high intraspecific morphological variability and distinct granulation on septal faces. Ontogenetic development indicates that corallites show hexameral septal arrangement and cyclic mode of insertion. The genus has no specific morphologies that deny scleractinian affinities. Numidiaphyllum is believed to have originated in sponge-algal reefs in the Permian tropics but possesses a basic scleractinian form which was already established in Early Palaeozoic times. Whatever their variation might be, the zoantharians, which may be closely related to Numidiaphyllum, survived the end-Permian extinction in 'deep-water' refuges as Permian holdovers, retaining their body plan, and they are possible scleractinian ancestors in the Triassic. Scleractinia have no immediate phylogenetic relationship to Rugosa. This study provides evidence about Permo-Triassic anthozoan phylogeny in terms of Permian survivors and their relationship to Triassic scleractinian origins.