Abstract

New collections from measured sections provide much of the material for this study. Holcocystis, Atopocystis, and Stummelasma are erected as new genera. Atopocystis mucronata and Stummelasma sulfurense are new species; Holcocystis flexa (Stumm), Stummelasma lonense (Stumm), and S. antelopense (Merriam) are new combinations. Revised coral ranges are integrated with the standard Nevada conodont zones and brachiopod-based faunal intervals. A range chart for 33 Rugosa emphasizes their value for correlation in Icriodus, or brachiopod-poor biofacies of the Great Basin. It also shows that full recovery from the end Lockhovian/early Pragian coral crisis in the region was delayed until the start of the middle Emsian gronbergi Zone. The recovery was accomplished principally by radiation of the Breviphyllidae and Papiliophyllidae, and by immigration of cyathophyllid and other genera.

Updated lists of Rugosa genera present in the Great Basin, Mackenzie, and Appohimchi provinces during the Pragian and early Emsian (kindlei-lenzi zones) and middle to late Emsian (gronbergi-serotinus zones) are given. Qualitative and quantitative data, the latter as Otsuka Coefficients, indicate that the Pragian Great Basin coral faunas can no longer be regarded as part of a temporary westward extension of the Eastern Americas Realm. Nor can they be considered part of the Mackenzie coral province. Genus absence/ presence data show that the Great Basin coral province began with a slow recovery of faunas after the late Lochkovian/early Pragian coral crisis, and ended with the arrival of typical Old World Realm families, including the Ptenophyllidae and Stringophyllidae, within the early Eifelian, costatus Zone. During this time faunas of the Mackenzie coral province were also distinct from those of the exotic Alexander and Farewell terranes of Alaska and British Columbia. The duration of the Devonian Great Basin coral province corresponds closely to the duration of a period of depressed seawater temperatures postulated from the distribution of gypidulinid brachiopods.

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