Biostratigraphy and taxonomy of Drumian (middle Cambrian) agnostid trilobites of the Manuels River Formation, Avalonian Newfoundland, Canada

Javier Álvaro,Christina Ifrim,Anne Hildenbrand,Gregor Austermann,Peter Bengtson

doi:10.1002/spp2.1358

Abstract

AbstractNew, accurately located and well‐preserved agnostid trilobite material has been collected from the type locality of the Drumian (middle Cambrian, Miaolingian) Manuels River Formation, Newfoundland, Canada. The well‐exposed grey to black shales containing the fauna were deposited on the former microcontinent Avalonia. Four interval zones for the succession are proposed, namely, the Tomagnostus fissus, Hypagnostus parvifrons, Ptychagnostus atavus and Ptychagnostus punctuosus zones. The Tomagnostus fissus and Ptychagnostus atavus zones are distinct from each other, which leads to a significantly shorter and stratigraphically higher Ptychagnostus atavus Zone compared with other sections (Scandinavia, South China, Utah and Nevada, Greenland). Specimens of Ptychagnostus atavus, however, occur abundantly, with 107 specimens identified in a short interval of the succession. The Ptychagnostus punctuosus Zone can be correlated globally. The faunal assemblage is comparable to that of Scandinavia, Greenland and England. Ptychagnostus affinis is recorded for the first time from Avalonia. The 1408 collected specimens were assigned to the suborders Agnostina and Eodiscina and to the families Peronopsidae and Ptychagnostidae, and Condylopygidae and Eodiscidae, respectively, with the following species: Peronopsis fallax (Linnarsson), Peronopsis scutalis (Hicks), Hypagnostus parvifrons (Linnarsson), Ptychagnostus punctuosus (Angelin), Ptychagnostus affinis (Brøgger), Ptychagnostus atavus (Tullberg), Tomagnostus fissus (Lundgren), Tomagnostus perrugatus (Grönwall), Pleuroctenium granulatum (Barrande) and Eodiscus punctatus (Salter).

Highlights

TRILOBITES of the Order Agnostida are common in Cambrian rocks and are important biostratigraphic tools, given their rapid evolution and wide distribution
New, accurately located and well-preserved agnostid trilobite material has been collected from the type locality of the Drumian Manuels River Formation, Newfoundland, Canada
The 1408 collected specimens were assigned to the suborders Agnostina and Eodiscina and to the families Peronopsidae and Ptychagnostidae, and Condylopygidae and Eodiscidae, respectively, with the following species: Peronopsis fallax (Linnarsson), Peronopsis scutalis (Hicks), Hypagnostus parvifrons (Linnarsson), Ptychagnostus punctuosus (Angelin), Ptychagnostus affinis (Brøgger), Ptychagnostus atavus (Tullberg), Tomagnostus fissus (Lundgren), Tomagnostus perrugatus (Gro€nwall), Pleuroctenium granulatum (Barrande) and Eodiscus punctatus (Salter)

Summary

Introduction

TRILOBITES of the Order Agnostida are common in Cambrian rocks and are important biostratigraphic tools, given their rapid evolution and wide distribution They are generally abundant in open-shelf facies from the middle Wuliuan Stage to the end of the Drumian Stage (Geyer & Shergold 2000; Peng & Robison 2000). In order to obtain material for a revision and refinement of the systematics and biostratigraphy of agnostid trilobites, specimens were collected bed by bed from the highly fossiliferous shales exposed at the type locality of the formation Kelligrews, Manuels and Topsail are within the city limits of Conception Bay South

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