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ISBN: 0-919216-84-6

ISSN: 0821-7556

Collections of silicified trilobite from the Whittaker Formation for two sections near Avalanche Lake, Northwest Territories, demonstrate faunal changes through the latest Ordovician, up to the base of the Silurian. The trilobites were collected from horizons of Edenian to Gamachian (latest Ordovician) in age, directly below the Ordovician/Silurian boundary. Thirty-three species, representing 15 families are identified in the two sections. Fifteen new species are identified, described, and classified. New species include Bumastoides solangeae, Bathyurus teresoma, Decoroproetus hankei, Isotelus dorycephalus, Anataphrus elevatus, Robergiella insolitus, Ampyxina pilatus, Cryptolithus altus, Acanthoparypha palmapyga, Acanthoparypha latipyga, Ceraurinella lamiapyga, Cybeloides acorni, Sceptaspis avalanchensis, Calyptaulax n. sp. A., and Hemiarges n. sp. A. Several previously established taxa are illustrated and discussed from this area, including Tricopelta mackenziensis Ludvigsen and Chatterton, 1982, Ceraurinella brevispina Ludvigsen, 1979, Ceraurus mackenziensis Ludvigsen, 1979, Ceraurinus serratus Ludvigsen, 1979, Borealaspis whittakerensis Ludvigsen, 1979, Cryptolithus tessellatus Green, 1832, and Harpidella kurrii Adrain and Chatterton, 1995b.

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Joint Committee on Paleontological Monographs

Softcover 87 pp., 21 pls. (2003)