Late Ordovician brachiopods Rafinesquina lata Whiteaves, 1896 and Kjaerina hartae n.sp. from southern Manitoba and the Hudson Bay Lowlands

Abstract

Examination of the Late Ordovician strophomenid brachiopod Rafinesquina lata Whiteaves, 1896 from the Selkirk Member of the Red River Formation of southern Manitoba reveals that the two syntypes actually represent two genera and two species, Oepikina lata and Kjaerina hartae n.sp. Specimens typically described as Rafinesquina lata by Whiteaves are large, thick-shelled, strongly but evenly concavo-convex, with randomly spaced, fine, concentric growth lamellae and a high ventral interarea. Affinity of the species to Oepikina lies in its unequal parvicostellae of the ventral valve, conspicuous dorsal peripheral rim, robust cardinal process, and strong lateral trans-muscle septa. Kjaerina hartae is easily distinguished from O. lata by its strongly geniculate and less massive shell, a much lower ventral interarea, prominent concentric rugae, and, internally, considerably weaker trans-muscle septa. The shells of O. lata and K. hartae are unusually large and suggest an open, shallow- and warm-water, subtidal depositional environment for the original sediments of the Selkirk Member of the Red River Formation. Common occurrences of K. hartae in the upper Portage Chute and Surprise Creek formations (Bad Cache Rapids Group) of the Hudson Bay Lowlands, together with other brachiopods and other groups of fossils, support the concept that the epicontinental seas once covering the Hudson Platform and the Williston Platform were connected during Late Ordovician (Maysvillian) time.