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Late Ordovician and Silurian lichid trilobites from northwestern Canada: Hemiarges, Borealarges, and Richterarges

Published online by Cambridge University Press:  14 July 2015

Margaret J. Campbell  and
Brian D. E. Chatterton
Margaret J. Campbell
Affiliation:
Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, T6G 2E3 Canada
Brian D. E. Chatterton
Affiliation:
Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, T6G 2E3 Canada
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Abstract

Four new species of Borealarges, B. fritillus, B. patulus, B. renodis, and B. variabilis, and one new species of Richterarges, R. facetus, are described and one unnamed species, Borealarges sp., discussed. All are from the Wenlock strata of Avalanche Lake sections in the Mackenzie Mountains, Northwest Territories. Borealarges tuckerae Adrain, 1994, the only species reported from both the Arctic and the Mackenzie Mountains, is discussed. Hemiarges avalanchensis n. sp., an Ashgill species from Avalanche Lake section AV 4B just below the Ordovician-Silurian boundary, is described. A phylogenetic analysis based on 14 species of Borealarges, three of Richterarges, and two of Hemiarges, demonstrates that the former two genera are three separate and distinct taxa. Borealarges, a genus that includes some species formerly assigned to Richterarges or Hemiarges, is monophyletic, contains a well-supported internal clade of species, and is not separated into senso stricto and senso lato groupings.

Type
Research Article
Information
Journal of Paleontology , Volume 81 , Issue 6 , November 2007 , pp. 1348 - 1364
Copyright
Copyright © The Paleontological Society 

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