Bathymetry of Early Middle Ordovician [Chazy] ostracodes, Lower Esbataottine Formation, District of Mackenzie

Abstract

Silicified specimens of 26 genera of early Middle Ordovician (Chazyan) ostracodes occur in two sections of the lower Esbataottine Formation in southwestern District of Mackenzie . Many of these ostracode genera are widespread in the upper Tulip Creek - lower Bromide formations of Oklahoma; the upper New Market - Lincolnshire - lower Edinburg formations of Pennsylvania and Virginia; and the Day Point - Crown Point - lower Valcour formations of New York. By means of a bathymetric succession of trilobite biofacies already proposed for plat{ orm carbonate strata of the lower Esbataottine Formation, a shallow-water widespread ostracode assemblage I (=Bathyurus-Isotelus bi of acies) and a deeper water ostracode assemblage II (=Calyptaulax-Ceraurinella - proximal Dimeropyge bi of acies) may be distinguished . These ostracode assemblages occur with some modification elsewhere in North America and may be used for the first time to indicate the relative bathymetry of comparable faunas from widely separated segments of the early Middle Ordovician North American continental platform . Five new genera (Palaeocopida: Eurybolbina, Nahanniopsis, Canadabolbina, Valcouropsis; Podocopida: Bolboscapha) and twelve new species are erected. In addition, taxonomic revisions and observations are presented for some previously incompletely known North American Chazy ostracode species and for those taxa observed during the study that may have affinities with Middle Ordovician ostracode faunas from Europe. At present, faunas from both regions require additional detailed study before intercontinental biogeographic considerations may be attempted

Soft Body-Related Features of the Carapace and the Lifestyle of Paleozoic Beyrichioidean Ostracodes

“…2: 3, 7-9) have their velum developed spine−like posteroventrally. This is in contrast with the situation in E. krafti (Copeland 1982 Levisulculus smolai Schallreuter and Krůta,1991 is also assigned to the genus Eurybolbina. In this species the S2 is much more distinct than in the type species Krůta 1991, 2001: fig.…”

“…118: 1, 3). Also females of E. bispinata (Copeland 1982: pl. 2: 3, 7-9) have their velum developed spine−like posteroventrally.…”

“…The holotype of E. bispinata-a tecnomorphic juvenile carapace (not an adult male)-lacks a velum in the posterior re− gions and the velar frill terminates spine−like posteroventrally (Copeland 1982: pl. 2: 10; Williams and Miller 1992: pl.…”

“…For C. obliqua Kraft, 1962, Copeland (1982 intro− duced the new genus and species Eurybolbina krafti, which should be distinct from C. obliqua by the missing postero− ventral "tubercle". Williams and Miller (1992: 115) consid− ered E. krafti as a synonym of E. bispinata (Harris, 1957) and this nominal species tentatively as a synonym of C. obliqua (E. ulrichi).…”

Morphology and affinities of Eridostracina: Palaeozoic ostracods with moult retention

“…Casier & Devleeschouwer (1995) noted the presence of abundant specimens of Cryptophyllus sinsinensis in a rich, but poorly diversified supposed shallow marine assemblage in the lower part of the Famennian in Sinsin (Dinant Basin, Belgium). Copland (1982) suggested that the Middle Ordovician Cryptophyllus fauna of North America inhabited a deep platform environment. Jones (1989) and Bless (1983) suggested a marine nearshore realm for Cryptophyllus in the Late Devonian and Early Carboniferous of Western Australia and the Late Devonian of Western Europe.…”