ORDOVICIAN AND SILURIAN CORALLINE RED ALGAE

Solenopora gotlandica Rothpletz, hitherto placed in the Solenoporaceae Pia, is locally common in the mid-Silurian of Gotland and Wales. It p ossesses small cells, radial monomerous thallus organization, trichocy tes, and sporangia arranged in irregular sori. Solenopora gotlandica i s not congeneric with S. spongioides, the type species of Solenopora. It closely resembles the errant coralline red alga Sporolithon Heydric h. S. gotlandica is here transferred to Craticula gen. nov., and Crati cula is placed in the Craticulaceae fam. nov., which morphologically c losely resembles the Mesozoic-Cenozoic family Sporolithaceae. The Crat iculaceae is placed in the extant rhodophyte order Corallinales. Middl e-Late Ordovician Petrophyton kiaeri Hoeg resembles Late Ordovician So lenopora richmondense Blackwell et nl., which has sporangia in calcifi ed compartments arranged in sori. These fossils may be craticulaceans. The apparent gap in the fossil record between Silurian Craticula and Cretaceous Sporolithon favours separation of these genera at family le vel. However, future work may demonstrate that the Craticulaceae is a junior synonym of the Sporolithaceae. Recognition of the Craticulaceae extends the earliest record of the Corallinales from Cretaceous to Si lurian, and possibly Ordovician.