Middle Devonian Brachiopods from Arctic Canada and Some Preliminary Results of North American Biogeography Based on Quantitative Assessment

摘要

INTRODUCTION The upper Lower to Middle Devonian Bird Fiord Formation (late Emsian to late Eifelian) is a carbonate-siliciclastic succession that contains a diverse brachiopod-dominated fauna. A collection of over 45 000 brachiopod specimens, which came from 140 collections made at 34 locations throughout the outcrop belt of this formation, contains 22 species of brachiopods that belong to 21 genera. Among them, the atrypids form 52% of the biota, spiriferids ～13%, orthids ～8%, productids ～3%, rhynchonellids ～2%, terebratulids ～1% and the strophomenids, pentamerids, and athyridids each <1%. Spinatrypina, Schizophoria, Elythyna, Desqumatia (Independentrypa), Cupularostrum, and Atrypa collectively form more than 80% of the brachiopod biota.