Lower Carboniferous sponges from the Craven Reef Belt of North Yorkshire

Abstract

SUMMARY Fossil sponges are significant elements in framework facies of Late Visean Cracoean reefs of northern England. In the Craven Reef Belt (North Yorkshire), lithistid demosponges, including Scheiia castletonense (Wolfenden 1959), Haplistion carbonaria (Wolfenden 1959) and Haplistion mega sp. nov., occur along with the less abundant, sphinctozoid demosponge Sollasia ramosa sp. nov. in this facies. Scheiia castletonense is an irregular globose to mound-shaped tricranocladinid hindiid sponge with irregular secondary branchlike growths in which the canal and skeletal structure are continuous with those of the globular part of the sponge. Both species of Haplistion are rhizomorinid lithistid sponges. Haplistion mega is a lobate sponge characterized by moderately coarse skeletal tracts that are relatively far apart, in contrast to the fine tracts and closer spacing in the more common globose to subspherical Haplistion carbonaria . The aporate ‘sphinctozoan’ Sollasia ramosa, commonly appears in the available sections as isolated spherical chambers because of its relatively loose branching habit and the beadlike to moniliform series of spherical chambers in each branch.