MIDDLE CAMBRIAN AGNOSTID TRILOBITES FROM THE MANUELS RIVER FORMATION, AVALON PENINSULA NEWFOUNDLAND, CANADA: THEIR PALAEOBIOGEOGRAPHIC RELATIONS AND IMPLICATION FOR PALAEOGEOGRAPHY

Agnostid trilobites of the Drumian (middle Cambrian) Manuels River Formation were studied in its type locality, a classic Cambrian outcrop in Manuels River, Newfoundland, Canada. The grey to black shales containing the fauna, were deposited on the former microcontinent Avalonia. The agnostids were determined by use of modern systematic concepts and were assigned to the suborders Agnostina and Eodiscina, families Peronopsidae, Ptychagnostidae, Condylopygidae and Eodiscidae, genera Peronopsis Hawle and Corda, 1847, Hypagnostus Jaekel, 1909, Ptychagnostus Jaekel, 1909, Tomagnostus Howell, 1935, Pleuroctenium Hawle and Corda, 1847, and Eodiscus Hartt in Walcott, 1884, and the species Peronopsis fallax (Linnarsson, 1869), Peronopsis scutalis (Hicks, 1872), Hypagnostus parvifrons (Linnarsson, 1869), Ptychagnostus punctuosus (Angelin, 1851), Ptychagnostus affinis (Brøgger, 1879), Ptychagnostus atavus (Tullberg, 1880), Tomagnostus fissus (Lundgren in Linnarsson, 1879), Tomagnostus perrugatus (Grönwall, 1902), Pleuroctenium granulatum (Barrande, 1846) and Eodiscus punctatus (Salter, 1864). Based on that, agnostid biozones can be differentiated within the Manuels River Formation and correlated to other middle Cambrian exposures (e.g. Gondwana). Detailed systematic analysis of the fauna allows interpretation on palaeobiogeographic affinities previously unrecognized, including a new interpretation of the position of Avalonia relative to the surrounding continents.