Systematics and evolution of cyathophylloidid and stauriid rugose corals (late ordovician–mid-silurian)

Rugose corals attributed here to the families Cyathophylloididae and Stauriidae are common and internationally widespread in the Upper Ordovician-Wenlock strata. They were formerly considered as closely related constituents of the Stauriidae. Here, based on the described, mostly type material mainly housed at palaeontological institutions of China and Estonia, as well as a few new specimens, a great many taxa of the two families are systematically revised, and a comparative study of all known records is performed. The study highlights the evolutionary and taxonomic significance of modes of corallite increase. The Cyathophylloididae, consisting of Palaeophyllum, Cyathophylloides, Favistina, Crenulites and Palaeolithostrotion, is defined here as a group of non-dissepimented Stauriida exhibiting exclusively lateral increase. In contrast, the Stauriidae consists of Stauriida characterised by a septal parricidal increase (new term), in which new separating walls are formed from pre-existing