NOTA SOBRE LA VALIDEZ DE FISSIRHYNCHIA PEARSON, 1977 (BRACHIOPODA, RHYNCHONELLIDA)

Abstract

The object of this note is to try to clarify the delicate situation concemíng the rhynchonellíd species "Blumchonella" [issicostata Suess, 1854, whích in the last few years has been independently related to at least four different, newly erected, nominal genera: al Costirhynchia Dagís, 1974 (type-species: C. spatiosa Dagis, 1974, from the Carnian of northwest Caucasus}, in fact a junior homonym of Costirhynchia S. Buckman, 1918 (type-specíes: C. costigera Buckman, 1918, from the Aalenian of Great Britain); b) Eoseptaliphoria Ching & Sun, 1976 (type-species: E. tulungensis Ching & Sun, 1976, from the early Norian of Tibet ; e) Fissirhynchia Pearson, 1977 [first quarter] (type-species: R. fissicostata Suess, from the Rhaetian of Walleg, Austria); d) Costirhynchopsis Dagis, 1977 [thírd quarter], a replacement name for Costirhynchia Dagis non Buckman, therefore automaticaJly taking the same type-species. All these generic entities, as understood by their respective authors, are extremely closely related and mutuaJly overlapping in their scope, specially relying upon external haracters alone.A closer look at published internal features, however, reveals slight differences in inner structure such as a brachíal septum of moderate length but consistently low from the plane of articulation onwards in one group of species like C. spatiosa Dagís and F. fissicostata (Suess), whilst other group of species including E. tulungensis Ching & Sun and E. intorta Ching & Sun share a longer and conspicuously higher brachial median septum. Pending additional knowledge of the internal characteristics of other species of intermediate or dubious position, with the evidence at hand the best procedure would be: To accept Fissirlujnchla as senior ubjective synonyrn into which, in addition to Rhaeto-Liassic species (e.g.: Fissirhynchia fissicostata), the bulk of Triassic species included by Dagis in bis pre-occupied genus Costirhynchia (Iater = Costirhynchopsis) could be accomodated; whilst the rest of the species concerned would fit into osepialiphoria in a restricted sense, encompassing those forms bearing a higher median septum.