Corals not serpulids: mineralized colonial fossils in the Lower Jurassic marginal facies of South Wales

Poorly preserved colonial corals occur near the base of the Lower Jurassic marginal facies at Southerndown, South Wales. Previously they have been interpreted as serpulid colonies, despite a dissimilarity to any serpulids known from elsewhere in the Lias or the few known extant colonial serpulids. However, local preservation of fine detail reveals evidence, in the form of corallites, septa and tabulae, that they are scleractinian corals of the Suborder Faviina, Family Stylophyllidae. These coral specimens occur in close association with barite–galena veins in the underlying Carboniferous Limestone and adjacent Lias marginal facies. Their widespread misindentification as ‘serpulid reefs’ is a consequence of coarse replacive mineralization by barite, which has largely obscured the diagnostic characters.