Diffingiina subordo n., tentatively included in Stauriida Verrill, 1865, is characterized by the adaxial split of the inner end of at least one (the cardinal) septum; the development of the basal plate and the vertical position of the young corallite at the beginning of its growth; the absence of septal furrows; the shortening of the counter septum at least during some part of the neanic growth; the trabecular microstructure of septa; and the biform tabularium. The attachment scars have once been illustrated for the Rugosa, but they were recognized only in this paper. All taxa included in the suborder are new, because their basic characteristics have not been reported so far as present in the Rugosa. Two new families have been established: the monotypic family Plerodiffiidae fam.n ., containing only a single species Plerodiffia eaglebuttensis sp.n., and the family Diffingiidae fam.n. subdivided into two subfamilies. In the monotypic subfamily Diffingiinae subfam.n. seven new species have been recognized. The presence of two opposite trends in the morphological development suggests the possibility of further increase in the number of genera within the subfamily. The subfamily Turgidiffiinae subfam.n. contains two genera: Turgidiffia gen.n. with three new species and the new genus and species left in the open nomenclature.

Key words: Rugosa, new suborder, morphogenesis, systematics , Permian, SW Texas.