A new Early Devonian (Emsian) arthrodire from the Northwest Territories, Canada, and its significance for paleogeographic reconstruction

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Schultze, Hans-Peter, Cumbaa, Stephen L.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2017
• Subjects: New Siberian Islands; Northwest Territories; Svalbard; Spitsbergen
• Online Access: http://dx.doi.org/10.1139/cjes-2017-0013; http://www.nrcresearchpress.com/doi/full-xml/10.1139/cjes-2017-0013; http://www.nrcresearchpress.com/doi/pdf/10.1139/cjes-2017-0013

An heterostiid arthrodire, Herasmius dayi sp. nov., is described from upper Lower Devonian marine deposits of the Bear Rock Formation along the Anderson River, Northwest Territories, Canada. New elements described for the genus for the first time include the suborbital, submarginal (also new for the family Heterostiidae), the lateral shoulder girdle with posterior lateral, anterior dorso-lateral, and posterior dorso-lateral plates and possible infragnathal plate. We present a new reconstruction of the cranial region of Herasmius, previously known only from supposedly freshwater – shallow marine deposits of roughly the same age in the Wood Bay Group of Spitsbergen. The late Early Devonian fishes that are common to the Arctic region of northwestern Canada and the island of Spitsbergen in the Svalbard archipelago of Norway, the porolepiform Heimenia and the arthrodire Herasmius described here, demonstrate the existence of a barrier-free paleogeographic connection between those continental blocks by the late Early Devonian. Comparison of the entire Anderson River vertebrate fauna with other boreal faunas of similar age indicates additional paleogeographic connections north of and around the Old Red Sandstone Continent to the Baltic region, central Europe, and even to the New Siberian Islands and South China, in contrast to most current published paleogeographical reconstructions.