Brachiopodes du Dévonien Inférieur et Moyen des formations de Blue Fiord et Bird Fiord des Îles Arctiques Canadiennes

Abstract

The brachiopods (Pentamerida, Rhynchonellida, Spiriferidina) that are described and illustrated are from the Blue Fiord, Bird Fiord and comparable formations of the Canadian Arc tic Islands, principally from Ellesmere, Devon and Bathurst Islands. The brachiopods were selected from numerous collections of fossils made by the Geological Survey of Canada during Operation Franklin (1955) and in subsequent field studies. The brachiopod faunas obviously are st rongly endemic in character; of the more than thirty species or subspecies identified, ten belong to genera or subgenera of limited geographic provenance, twenty-five are restricted to the Arctic and among these, twenty-one are new taxa. These are: Pentamerida: Carinagypa (Aseptagypa) maclareni, Ivdelinia grinnellensis, I. (Ivdelinella) ellesmerensis; Rhynchonellida: Ancillotoechia? ventricosa variabilis, Cupularostrum? pentagonale, C. ? ellesmerense, Camarotoechia s. l. pseudomedea, Hypothyridina bifurcata, Cassidirostrum vexans arcticum, Athyrhynchus susanae intermedius, A. sverdrupi eosverdrupi, A. trilobatus; Spiriferidina: Fimbrispirifer? pseudoscheii, F. fascicostatus, Warrenella disjuncta, W. franklini praefranklini (typical and transverse forms), W. collina arctica, W. pseudaequabilis, W. (Warrenellina) extensa, Emanuella bisiruata, Elythina sverdrupi. A considerable number of forms at present remain generically or specifically undetermined, because of insufficient material to allow reliable determination. The faunas of the two formations, especially that of the lower part of Blue Fiord Formation, clearly are related to Nevada faunas. At the close -of the Early Devonian, the Arctic Islands belonged to the same faunal province as Nevada and the Yukon. This province has been named the Cordilleran subprovince by Boucot et al. (1967) and considered by them to be a subprovince of the Old World Province. This connection between the Arctic Islands and Nevada continued at least for a part of the Middle Devonian, that is until the close of Blue Fiord sedimentation. These conclusions are deduced from the appearance at certain times of a number of common genera or species in the faunas of the two regions. These same elements are used to establish the following correlations which form the prime evidence of the ages of the rock units: (1) the Nevada zone of Eurekaspirif er pinyonensis (dated as Emsien) with the lower part of the lower member of the Blue Fiord Formation in the type locality; (2) the Nevada Zone of Leptathyris circula and the lower part of that of Warrenella kirki (dated as Eifelien) with the upper part of the lower member and the lower part of the upper member of Blue Fiord Formation in the type locality. The age of the Blue Fiord Formation at its type locality and in the other areas in which it outcrops is deduced principally from these correlations. The Bird Fiord Formation is dated at its type locality and in other parts of Devon and Ellesmere Islands as probably Late Eifelien but as probably Givetien in Bathurst Island, inferred principally from the distribution of certain brachiopod genera (Ivdelinia, Hypothyridina, Cupularostrum and Elythina). Among the representatives of these three groups of brachiopods, some elements show relationships with faunas from northeastern Russia, while some others have Appalachian or European affinities. The distribution of species within the Blue Fiord and Bird Fiord Formations at their type localities provides a basis to discuss !and in some cases to make more precise) correlations previously proposed by authors between these sections and rock units at other localities in the Arctic Islands where these formations have been reported.

On the genusQuiringitesStruve, 1992 (Brachiopoda, Middle Devonian)

“…But even though they are poorly illustrated, the figured specimens do not resemble Q. elegans because of the smaller number of plications. Brice (1982) figured specimens similar to the ones of Meyer (1913) from the Blue Fiord Formation of the Canadian Acrtic Islands under the name ?Adolfia (Gürich, 1909), which have clearly developed deltidial ridges and an angular sulcus. Both morphological characters are lacking in Q. elegans.…”

A new species of Ivdelinia Andronov, 1961 from the Moroccan Givetian and its palaeoecological and palaeobiogeographical implications

“…Additionally, as already proposed by Blodgett & Boucot (1999) and , a closer relationship of SW Alaska to the Urals than to the Canadian Arctic Islands appears plausible. Even though a single species of Ivdelinia occurs in the Canadian Arctic Islands and suggesting a faunal migration, the subgenus Ivdelinella Brice, 1982 seems to be endemic for this region. The species Ivdelinia (Ivdelinella) salairica Gratsianova, 1998 would be the first taxon within this subgenus from Emsian strata; due to the lack of plications or only faint plications on the dorsal valve and the lack of the median septum we attribute this taxon to Carinagypa Johnson & Ludvigsen (1972) (personal communication R.B.…”

“…Furthermore, the plications on the fold, sulcus, and flanks are of equal size. Brice (1982) described I. grennellensis Brice, 1982 from the Arctic Canadian Islands. This species has a shorter ventral median septum, a more compact form, and 4 ribs on the fold.…”

“…Malygina & Sapelnikov (1973) and Sapelnikov (1985) described further taxa from Lower Devonian and Eifelian strata of the Ural Mountains and Central Asia. Brice (1982) subdivided the genus into two subgenera with material from Arctic Canada based on the presence and absence of a ventral median septum. Blodgett & Boucot (1999) reported the first species from Alaska and proposed its relationship to Ivdelinia species from the Urals.…”

New interpretations of the phylogeny and taxonomy of delthyridoid spiriferids (Brachiopoda, Lower and Middle Devonian)

“…2A), however, on most of the material, including the holotype of the type species, the micro-ornamentation is not preserved. Thus, various authors assigned spiriferids to Fimbrispirifer emphasizing their bifurcating ribs and ribbed fold and sulcus rather than by the micro-ornamentation, which is only preserved in rare cases (e.g., Amsden 1963, Brice 1982. Havlíček (1959) defined Fimbrispirifer by simple and bifurcating ribs and ribs on flanks, fold, and in sulcus with a fimbriate micro-ornamentation.…”