Systematics of Encrinuroides and Curriella (Trilobita), with a new Early Silurian encrinurine from the Mackenzie Mountains

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Edgecombe, Gregory D., Chatterton, Brian D. E.
• Format: Article in Journal/Newspaper
• Language: French
• Published: Canadian Science Publishing 1990
• Subjects: General Earth and Planetary Sciences; Northwest Territories; Weller; Mackenzie mountains
• Online Access: http://dx.doi.org/10.1139/e90-085; http://www.nrcresearchpress.com/doi/pdf/10.1139/e90-085

Encrinuroides Reed, 1931 has been diagnosed as a paraphyletic ancestral taxon since its inception. Cladistic parsimony analysis of "Encrinuroides" species most closely related to the Silurian Encrinurus plexi discovers two shortest-length cladograms (consistency index = 0.68) based on 28 exoskeletal characters. Curriella Lamont, 1978 is revised to include Curriella clancyi n.sp., based on silicified material from earliest Llandovery strata of the Whittaker Formation in the Mackenzie Mountains, Northwest Territories. The new species is most closely related to the Scottish Llandovery type species, Curriella newlandensis Lamont, 1978 (for which type specimens are figured) and Curriella tuberculifrons (Weller, 1907) from Illinois. This Silurian clade is sister group to stratigraphically early Chinese "Encrinuroides" species and the monophyletic Encrinurus plexi. Certain Appalachian Caradoc taxa and Erratencrinurus Krueger, 1972 are more closely related to this group than to many other "Encrinuroides" spp. Further taxonomic revision should exclude these species from Encrinuroides (s.s.), which can be appreciably restricted in scope.