Chondrichthyan biofacies in the Late Famennian of Utah and Nevada

Late Famennian assemblages of chondrichthyan microremains, especially teeth, from Nevada and Utah representing two zones of different water depth are analysed and compared to formerly described pelagic chondrichthyan biofacies from the areas between S Euramerica and NW Gondwana. The assemblage from the deeper (deep to moderately deep subtidal) zone is comparable to the Phoebodus-Thrinacodus biofacies, but it lacks such typical forms as Ph. gothicus and Th. tranquillus. The assemblage from the shallower (shallow subtidal) zone might be an equivalent of the Protacrodus biofacies from which it differs in containing Th. ferox and some other shallow water taxa, thus far unknown or very rarely found from the Famennian of central Europe and Africa. New definitions of chondrichthyan biofacies are proposed.