Brachiopods from the Lower Shale Member of the Williams Island Formation (Middle Devonian) of the Hudson Platform, northern Ontario and southern District of Keewatin
Authors: Norris A W 
Published: April 2015

Twenty-seven brachiopod taxa, eight of which are new, are described from the lower shale member of Williams Island Formation sampled at three principal localities as follows: 1) northeast bank of Albany River; 2) unnamed island on Abitibi River; and 3) south end
of Mid-Bay Shoal in Hudson Bay. The fauna from Locality 1 is dominated by new species and subspecies of Mucrospirifer, Desquamatia (Independatrypa) sanfordi n. sp., Devonochonetes sp. cf. D. scitulites (Cooper), and Spinocyrtia sp. cf. S. mourantae Ehlers and Wright. The fauna from Locality 2
includes Spinatrypina abitibiensis n. sp. Forms A and B, Elita lemoni n. sp., Athyris sp., and Floweria? sp. cf. F.? crassa (Imbrie). The more abundant and important brachiopods from Locality 3 include Mucrospirifer sp. cf. M. profundus (Grabau), M. sp. cf. M. thedfordensis (Shimer and Grabau), and
Rhyssochonetes? sp. The brachiopods are closely comparable to taxa from the lower and middle Hamilton Group of southwestern Ontario and New York State, and lower and middle Traverse Group of Michigan and adjacent states, ranging from the ensensis Zone to Middle varcus Subzone of late Eifelian to
mid-Givetian age. These brachiopod occurrences are from the most northerly parts of the Michigan Basin�Hudson Platform Province of the Eastern Americas Realm so far discovered in east-central North America. The presence of Rhyssochonetes? sp. at Locality 3 indicates a rise in sea level and migration
of fauna from west to east across the Transcontinental Arch from the Cordilleran Province of the Old World Realm during Middle varcus Subzone (Givetian) time. Twenty-seven brachiopod taxa, eight of which are new, are described from the lower shale member of Williams Island Formation sampled at three
principal localities as follows: 1) northeast bank of Albany River; 2) unnamed island on Abitibi River; and 3) south end of Mid-Bay Shoal in Hudson Bay. The fauna from Locality 1 is dominated by new species and subspecies of Mucrospirifer, Desquamatia (Independatrypa) sanfordi n. sp., Devonochonetes
sp. cf. D. scitulites (Cooper), and Spinocyrtia sp. cf. S. mourantae Ehlers and Wright. The fauna from Locality 2 includes Spinatrypina abitibiensis n. sp. Forms A and B, Elita lemoni n. sp., Athyris sp., and Floweria? sp. cf. F.? crassa (Imbrie). The more abundant and important brachiopods from
Locality 3 include Mucrospirifer sp. cf. M. profundus (Grabau), M. sp. cf. M. thedfordensis (Shimer and Grabau), and Rhyssochonetes? sp. The brachiopods are closely comparable to taxa from the lower and middle Hamilton Group of southwestern Ontario and New York State, and lower and middle Traverse
Group of Michigan and adjacent states, ranging from the ensensis Zone to Middle varcus Subzone of late Eifelian to mid-Givetian age. These brachiopod occurrences are from the most northerly parts of the Michigan Basin�Hudson Platform Province of the Eastern Americas Realm so far discovered in
east-central North America. The presence of Rhyssochonetes? sp. at Locality 3 indicates a rise in sea level and migration of fauna from west to east across the Transcontinental Arch from the Cordilleran Province of the Old World Realm during Middle varcus Subzone (Givetian) time. Vingt-sept taxons
de brachiopodes, dont huit nouveaux, sont décrits. Ils proviennent du membre de shale inférieur de la Formation de Williams Island, en particulier des localités principales suivantes : 1) rive nord-est de la rivière Albany; 2) île sans nom dans la rivière Abitibi; et 3)
extrémité sud du Haut-fond médian dans la baie d'Hudson. La faune de la localité 1 comprend surtout de nouvelles espèces et sous-espèces de Mucrospirifer, Desquamatia (Independatrypa) sanfordi n. sp., Devonochonetes sp. cf. D. scitulites (Cooper) et Spinocyrtia sp. cf.
S. mourantae Ehlers et Wright. La faune de la localité 2 comprend Spinatrypina abitibiensis n. sp. Formes A et B, Elita lemoni n. sp., Athyris sp. et Floweria? sp. cf. F.? crassa (Imbrie). Les brachiopodes les plus abondants et les plus importants de la localité 3 sont Mucrospirifer sp.
cf. M. profundus (Grabau), M. sp. cf. M. thedfordensis (Shimer et Grabau) et Rhyssochonetes? sp. Les brachiopodes se comparent étroitement aux taxons des parties inférieure et intermédiaire du Groupe de Hamilton dans le sud-ouest de l'Ontario et l'État de New York, et des parties
inférieure et intermédiaire du Groupe de Traverse dans le Michigan et les États adjacents. Ils vont de la Zone à ensensis à la Sous-zone intermédiaire à varcus de l'Eifélien tardif au Givétien moyen. Ces occurrences de brachiopodes se rencontrent dans les
parties les plus septentrionales de la Province du bassin du Michigan�Plate-forme d'Hudson du Domaine de l'est des Amériques découvertes à ce jour dans le centre-est de l'Amérique du Nord. La présence de Rhyssochonetes? sp. à la localité 3 indique une hausse du
niveau de la mer et une migration des faunes de l'ouest vers l'est en travers de l'Arche transcontinentale, à partir de la Province cordillérienne du Domaine de l'Ancien monde, durant l'époque de la Sous-zone intermédiaire à varcus (Givétien).