Article: Correlation of the Canadian Middle Devonian Hume and Nahanni formations by tetracorals
Dendrostella trigemme (Quenstedt), Grypophyllum graciliseptatum sp. nov., Utaratuia laevigata Crickmay, Sociophyllum glomerulatum (Crickmay), and Radiastraea verrilli (Meek) are shown to be common to the Hume and Nahanni Formations. In addition Taimyrophyllum, a senior synonym of Eddastraea, is recognized for the first time in North America, T. triadorum sp. nov. is described from the Hume Formation, and a closely related species T. vescibalteatum sp. nov. from the Nahanni Formation.Grypophyllum gracile (McCoy), from the Middle Devonian of Devon, is redescribed and a lectotype chosen.In some far northern regions there are indications that the lowest part of the Hume Formation may be Eifelian and in the upper Root River area there is evidence that the very uppermost Nahanni Formation is Middle Givetian. Elsewhere, however, the Hume, Nahanni and Headless Formations are believed to be essentially correlatives and early Givetian in the Belgian usage of the stage.