There are important morphological differences between the dominant higher taxa (classes) in associations of radiolarians that lived at different depths of paleobasins. A similar inversion of dominant radiolarian taxa can be seen in the Early Tournaisian (Mississippian) and the Kungurian (Cisuralian) and may indicate a change in their habitat from deeper conditions where porous Sphaerellaria dominant, to less deep-water shelf environments, in which spongy-lattice Spumellaria prevailed.