Lower Ordovician trilobites of the Oxford Formation, eastern Ontario

Abstract

The only Lower Ordovocian trilobites known to occur in Ontario are a small collection of generally poorly preserved asaphid, bathyurid, and pliomerid trilobites from the Oxford Formation in the area between Ottawa and Brockville. This fauna consists of Bolbocephalus convexus (Billings), Gignopeltis rarus (Billings), Goniotelina subrectus (Bradley), Strotactinus salteri (Billings), and Isoteloides sp. This fauna is late Canadian and early Arenigian in age. The trilobite, conodont, and mollusk faunas indicate correlations of the Oxford Formation with the Phillipsburg 'Series' of Quebec, Fort Cassin Formation of New York and Vermont, mid- to upper St. George Group of Newfoundland, and mid-Fillmore Formation of Utah. A neotype is chosen for Strotactinus salteri.

Ordovician trilobites from the Romaine and Mingan formations (Ibexian-late Whiterockian), Mingan Islands, Quebec

“…15, fig. 10) and the Oxford Formation of eastern Ontario (Ludvigsen, 1979b) is similar in the effacement of pleural furrows, but smaller and shorter (sag.). The Mingan Islands pygidium, however, is comparable to the larger hypotype from the Catoche Formation, St. George Group figured by Fortey (1979, pi.…”

Lower Ordovician trilobites from the Septembersø formation, North-East Greenland

“…rarus Billings, 1865), represented only by its holotype pygidium. Variably considered a probable junior synonym of Bolbocephalus (Fortey 1979, Ludvigsen 1979) and a possible senior synonym of Benthamaspis (Boyce 1989, Fortey & Bruton 2013 or Harlandaspis (Fortey & Bruton 2013), Adrain & Westrop (2005) correctly pointed out that G. rara has a margin that flattens posteriorly and comes to a subtle, spathulate point posteromedially, and the same morphology is also present in Strigigenalis cassinensis Whittington, 1953, albeit more strongly developed. They concluded that the taxa are related and that Gignopeltis has priority over Strigigenalis, but agreed with previous authors that Gignopeltis is best restricted to the holotype.…”

Lower Ordovician trilobites from the Baumann Fiord Formation, Ellesmere Island, Arctic Canada

“…truncatus Whitfield, 1890. REMARKS: Opinion has varied on the status of Gignopeltis Raymond, 1924, which is known from a unique holotype pygidium of the type species, Dolichometopus? rarus Billings, 1865, from the Oxford Formation of southern Ontario (see Ludvigsen, 1979). Ludvigsen (1979) and Fortey (1979) considered Gignopeltis a probable junior synonym of Bolbocephalus, based on similarity with the pygidium of Bolbocephalus convexus (Billings 1865).…”

“…rarus Billings, 1865, from the Oxford Formation of southern Ontario (see Ludvigsen, 1979). Ludvigsen (1979) and Fortey (1979) considered Gignopeltis a probable junior synonym of Bolbocephalus, based on similarity with the pygidium of Bolbocephalus convexus (Billings 1865). Boyce (1989) argued that it may instead be a synonym of Benthamaspis Poulsen, 1946.…”