Olenid-dominated trilobite fauna from the Shallow Bay Formation (Cow Head Group), Cambrian-Ordovician boundary interval, western Newfoundland

• Published in: Canadian journal of earth sciences Vol. 45; no. 4; pp. 407 - 425
• Main Author: Karim, Talia S
• Format: Journal Article
• Language: English
• Published: National Research Council of Canada 01.04.2008; NRC Research Press
• Subjects: Arthropoda; assemblages; biostratigraphy; Boeckaspis geordii; Cambrian; Canada; Cow Head Group; Eastern Canada; Invertebrata; invertebrate; Marine; morphology; new taxa; Newfoundland; Newfoundland and Labrador; Newfoundland Island; Olenidae; Ordovician; Paleontology; Paleozoic; phylogeny; Ptychopariida; Shallow Bay Formation; stratigraphic boundary; Stratigraphy; synonymy; taxonomy; Trilobita; Trilobites; Trilobitomorpha; type specimens; western Newfoundland; Newfoundland and Labrador; ANW, Canada, Newfoundland and Labrador, Newfoundland; Canada, Newfoundland, Cow Head Group
• ISSN: 0008-4077; 1480-3313
• DOI: 10.1139/E08-008

A single boulder (PH 8.14), recovered from unit 8 on the Point of Head, Cow Head Peninsula, Shallow Bay Formation (Cow Head Group), contains a unique olenid-dominated trilobite fauna composed of the following taxa: Boeckaspis geordii n. sp., Leiobienvillia terranovica (Rasetti, 1954), hystricurid n. gen. n. sp., Tulepyge sp. A, Tulepyge sp. B, Tulepyge? sp. C, and Symphysurina sp. The pelturine trilobite B. geordii dominates the assemblage. Boulder PH 8.14 consists of light grey-brown packstone to grainstone. This is atypical for olenid-dominated faunas, which usually occur in dark laminated limestones and shales. The fauna is likely earliest Ordovician in age, but a latest Cambrian age cannot be entirely ruled out. Regardless, this assemblage is unique in that it is the only known olenid-dominated fauna from Cambrian-Ordovician boundary sediments in Laurentia. A phylogenetic analysis of Boeckaspis and other putatively closely related taxa (Westergaardia Raymond, 1924 and Jujuyaspis Kobayashi, 1936) was conducted. The results of the analysis indicate that Westergaardia is not monophyletic and as such it is considered a junior synonym of Boeckaspis herein.