Lower Carboniferous solitary rugose corals from the Flett Formation of the Liard Basin, northwestern Canada vs. European and Asian Rugosa of the same geological age

Abstract

The paper focuses on the taxonomic description of the lower Carboniferous (uppermost Tournaisian to middle Viséan) solitary rugose corals from bedded limestone and shale units in the Flett Formation in the Jackfish Gap (eastern Liard Range), northwestern Canada. The corals described herein include 12 species representing the genera Ankhelasma Sando, 1961, Bradyphyllum Grabau, 1928, Caninophyllum Lewis, 1929, Cyathaxonia Michelin, 1847, Ekvasophyllum Parks, 1951, EnniskilleniaKabakovich in Soshkina et al., 1962, Vesiculophyllum Easton, 1944 and Zaphrentites Hudson, 1941. Two of these species are new Ankhelasma canadense sp. nov. and Ekvasophyllum variabilis sp. nov.) and 6 taxa are described in open nomenclature. The distribution and relative abundance of solitary Rugosa in Europe and the Liard Basin confirm the geographical proximity of those areas and the open marine communication between them during the early Carboniferous. It therefore represents an important contribution to the determination of the time of isolation of the western Laurussia shelf fauna from that of southeastern Laurussia, as well as the time of the possible emergence of species from southeastern Laurussia into the western aurussia seas. Of particular importance here are cosmopolitan taxa and the timing of their disappearance from the fossil record.