A new system of classification and phylogeny of three subtribes (of 12) of Cacteae, Pediocactinae, Thelocactinae, and Coryphanthinae, is briefly outlined. On the basis of new available data on seed morphology and anatomy of the tribe, published recently (Doweld, 1995), supplementing other available data on spine and areole morphology, flower and fruit structure, the generic circumscription of all three subtribes has been revised. The subtribe Pediocactinae, considered as a most archaic among all subtribes mentioned, is restricted only to include genera having variously developed tuberculate-papillate seed sculpturing types with granular cuticular sculpturing.

The recognition of the most primitive monotypic genus Meyerocactus, recently segregated from Echinocactus (Doweld, 1996), by its pediocactoid (aberrant for Echinocactus) seeds, fully debunks the concept of the polymorphic genus Pediocactus sensu Benson and validates the splitting of the genus into series of monotypic genera, such as Navajoa, Utahia, Puebloa, and Pediocactus s.str. The simply papillate seeds of Pediocactus s.str. are considered to be a connecting link between specialized Pediocactinae and advanced Thelocactinae which are characterized by papillate seeds. The Thelocactinae are re-circumscribed as consisting of 6 genera only: Thelocactus, Ancistrocactus, Neolloydia, Leuchtenbergia, Obregonia, and Stenocactus; all these genera have seeds with papillate (or secondary apapillate) seed sculpturing with granular cuticular sculpturing.

The subtribe Coryphanthinae is represented by 4 genera: Coryphantha, Escocoryphantha gen. nov., Lepidocoryphantha, and Cumarinia, which are limited to species having apapillate (smooth) seed sculpturing with faceted-granular or simply faceted (advanced feature) cuticular sculpturing; other seed types are excluded into other subtribes. The genus Lepidocoryphantha is treated as most archaic in Coryphanthinae, having peculiar seeds with granular cuticular sculpturing; it might serve a connecting link between relatively primitive Thelocactinae and advanced Coryphanthinae. A new genus, Escocoryphantha, is proposed to accommodate two species anomalous among Escobarias, E. chihuahuensis Br. et Rose and E. henricksonii Glass et Foster, which are closely related to Coryphantha bu their anomalous (for Escobaria) apapillate seeds with faceted granular sculpturing.

Judging by seed anatomy and morphology, Coryphanthinae are treated as closely allied to Pediocactinae-Thelocactinae, not to Echinocactinae or Cactinae as done by various authors; the resemblance with latter subtribes are exclusively of the convergent nature. The review and validation of other subtribes would be published elsewhere. 2 new taxonomic combinations were made to modify the taxonomy of the tribe Cacteae.