The British Lithostrotiontidae

Abstract

A revision and systematic study of the British species of the Carboniferous rugose coral family Lithostrotiontidae is described. No revision of this group has appeared since the middle of the last century. Results show that 15 described cerioid species of Lithostrotion can be lumped into four species. In addition L. decipiens depressum subsp. nov, is described in this group. The fasciculate species of Lithostrotion have been extended by the separation of L. variabile sp. nov., L. scaleberense sp, nov., L. junceum communicatum subsp. nov,, L. martini praenuntium subsp. nov. and L. martini simplex subsp. nov. The genus piphyphyllum is shown to be polyphyletically derived and its species are referred back to Lithostrotion. The monospecific genus Nemistium is considered synonymous with Lithostrotion and ranoved. Its one species is an evolutionary intermediate between two species of Lithostrotion. The genus Orionastraea is reviewed and 0. sera sp. nov. is described. Two species of Orionastraea are referred to Hadsonia gen, nov. which, though similar morphologically to Orionastraea, has a different ancestral species. H. matura Sp. nov. is described in this genua. The genus Aulina is excluded from the Lithostrotiontidae as it is thought to have different ancestors. It is restricted to include only forms with massive coralla and A. botanica sp. nov. and A. rotif ormis aphroidia subsp. nov, are described. Fasciculate species of Aulina are referred to Easoioaulina gen, nov. as they are apparently unrelated to Aulina sensu stricto. The phylogeny of the Lithostrotiontidae is described and shown to proceed by following certain evolutionary trends which lead to an increasing level of colonial it within the group. The evolutionary centre and therefore the palaeomigration directions of the Lithostrotiontidae are shown to change during the phylogeny and this is related to the global palaeogeography of the Carboniferous period. Discovery of well preserved material has allowed the skeletal changes during the hystero-ontogeny of L. martini to be determined. This revision has led to a better understanding of the species in the Lithostrotiontidae so that their value as statigraphical zonal indices has been increased.