Abstract

Since 1940, the Order Rhynchonellida has been extensively studied with considerable proliferation of genera; 138 in 1940 (Cenozoic and Mesozoic: 87; Palaeozoic: 51) against 286 in 1966 (Cenozoic and Mesozoic: 124; Palaeozoic: 162). The number of Palaeozoic genera has, thus, more than tripled in a quarter of a century.

In particular during this period, Devonian genera have increased from 17 to 86. Re-examination of the older genera mentioned in the literature has resulted in new definitions as well as the need to found new genera. These taxonomic units — redefined or new — already allow correlation between widely separated sedimentary basins, thus demonstrating that, although necessarily bound to facies, they are of considerable value in stratigraphy.

Famennian Rhynchonellida have been studied by the writer for some years. Five genera (Leiorhynchus Hall, 1860, Camarotoechia Hall and Clarke, 1893, Paraphorhynchus Weller, 1905, Pugnoides Weller, 1910, Calvinaria Stainbrook, 1945) that at one time or another had been considered Famennian, have now definitely been excluded from this interval. Fifteen genera have been accepted: Paurorhyncha Cooper, 1942, Zilimia Nalivkin, 1947, Plectorhynchella Cooper and Muir-Wood, 1951, (=Monticola Nalivkin, 1930), Basilicorhynchus Crickmay, 1952, Porostictia Cooper, 1955, Nyege Veevers, 1959, Eoparaphorhynchus Sartenaer, 1961, Ptychomaletoechia Sartenaer, 1961, Rugaltarostrum Sartenaer, 1961, Sinotectirostrum Sartenaer, 1961, Trifidorostellum Sartenaer, 1961, Evanescirostrum Sartenaer, 1965, Gastrodetoechia Sartenaer, 1965, Megalopterorhynchus Sartenaer, 1965, Physetorhyncha Sartenaer and Rozman, 1967. Three genera, of which the systematic position (Pugnax Hall and Clarke, 1893) or the stratigraphic range (Yunnanella Grabau, 1923, Nayunnella Sartenaer, 1961) are not fully understood, are still under examination. On the basis of some genera, it is already possible to outline the major trends of a world-wide biostratigraphic zonation of the Famennian.