Two kinds of cupulate seed plants are described from the Upper Devonian aged Upper Old Red Sandstone at Taffs Well near Cardiff. South Wales. The first conforms to the characters of Xenotheca devonica (Arber and Goode) Hilton and Edwards previously recognised from the Upper Devonian of North Devon, to which it is assigned. The Taffs Well specimens provide additional information on intraspecific variation within this morphospecies that is now known to possess 4-8 preintegumentary lobes in the distal 50-66% of preovule length. This represents the first occurrence of this morphospecies outside the type locality and highlights the morphological similarities observed in the morphogenera Xenotheca and Moresnetia and the genus Elkinsia. Cupules of the second kind occur terminally on a cruciately dichotomous branching system and have distinctive long and thin cupule tips. Cupules bear at least one asymmetric preovule that comprises an entire integument in the proximal 90% of preovule length and distally possess ca. 4 short and wide preintegumentary lobes. Features of its cupule and integument are distinct from all other recognised early seed plants leading to the establishment of Glamorgania gayerii gen. et sp. nov. Glamorgania shows that by the onset of the Carboniferous some seed plants had attained an almost complete integumentary surround. These records add to the growing body of data on the earliest seed plants and their initial phase of phenotypic radiation in the Upper Devonian. This investigation also highlights the problems of accommodating preservational differences in schemes of palaeobotanical nomenclature, from which it is concluded that Glamorgania may correspond to the compression/impression equivalent of the anatomically preserved Mississippian morphogenus Eurystoma. (c) 2006 Elsevier B.V. All rights reserved.