Article: Devonian corals and brachiopods from the Brendon Hills, west Somerset
The coral and brachiopod faunas of the Middle-Upper Devonian Ilfracombe Beds in the Brendon Hills, west Somerset, have been examined. The corals are restricted to two limestone horizons in the Ilfracombe Beds, the Rodhuish Limestone and the Roadwater Limestone; the brachiopods are sparse and more uniformly distributed throughout the succession. The rugose corals, Heterophrentis percevali sp. nov., Thamnophyllum caespitosum (Goldfuss), Acanthophyttum (Neostringophyllum) concavum (Walther) and Mesophyllum (Arcophylluni) sandhillense sp. nov.; a tabulate coral, Thamnopora polyforata (Schlotheim); and two brachiopods, Spinocyrtia ascendens (Spriestersbach) and Thomasaria gibbosa Vandercammen, are described. The coral and brachiopod faunas suggest that the bulk of the Ilfracombe Beds is Givetian; the Upper Hangman Grits and the lower part of the Ilfracombe Beds (the Avill Group) are Lower-Middle Givetian; the Cutcombe Slate and Rodhuish Limestone are Middle-Upper Givetian; and the Roadwater Limestone is Upper Givetian. The Givetian-Frasnian boundary probably lies within the Leighland Beds, towards the top of the Ilfracombe Beds. In the light of the present study, Wedekind's Middle Devonian rugose coral zonal scheme is seen to be in need of considerable modification.