Parastrophinella (Brachiopoda): Its paleogeographic significance at the Ordovician/Silurian boundary

1997 ◽  
Vol 71 (3) ◽  
pp. 369-380 ◽  
Author(s):  
Jisuo Jin ◽  
Paul Copper
Keyword(s):  
North America ◽  
Type Species ◽  
Late Ordovician ◽  
Eastern North America ◽  
Hudson Bay ◽  
Morphologic Change ◽  
Baffin Island ◽  
Median Septum ◽  
Lamellar Layer ◽  
Anticosti Island

The type species of Parastrophinella, P. reversa, a pentamerid brachiopod from the uppermost Ordovician (Hirnantian) Ellis Bay Formation of Anticosti Island, Quebec, shows that the genus is characterized by three features: 1) a ventral median septum apically buried in a thickened valve floor, but anteriorly rising above valve floor; 2) prominent alate plates, which are homologous to brachial processes; and, 3) a pseudocruralium consisting of a dorsal median septum, which is largely buried in the valve floor posteriorly, and outer plates that are connected to the median septum via prismatic substance (with poorly developed lamellar layer at the junctions) at, or slightly above, the valve floor. These constitute criteria by which many species previously assigned to Parastrophinella are excluded from the genus. Late Ordovician species that fit the redefinition of Parastrophinella are now confined to eastern North America. The genus crosses the Ordovician/Silurian boundary without major morphologic change, and Early Silurian species of Parastrophinella occur in both eastern North America and Great Britain. In the Late Ordovician, the pentamerid fauna of North America (Laurentia) contrasted sharply with that of Baltica and Kazakhstan, where the Holorhynchus fauna was dominant. Typical elements of the Holorhynchus fauna, such as the large-shelled Holorhynchus and Proconchidium, are known only in the northern parts of Laurentia (Baffin Island, Greenland, and Kolyma), and are absent in the Hudson Bay and Williston basins and southwards.

Late Ordovician - Early Silurian cryptospore occurrences on Anticosti Island (Île d'Anticosti), Quebec, Canada

2007 ◽  
Vol 44 (1) ◽  
pp. 1-7 ◽  
Author(s):  
Jeffery G Richardson ◽  
William I Ausich
Keyword(s):  
North America ◽  
Late Ordovician ◽  
Land Plants ◽  
Eastern North America ◽  
Upper Ordovician ◽  
Lower Silurian ◽  
Low Diversity ◽  
Anticosti Island ◽  
Early Land

Residues from Hirnantian (Upper Ordovician) and Aeronian (Lower Silurian) strata of Anticosti Island, Quebec, Canada, have yielded the oldest occurrence of terrestrial-based palynomorphs (cryptospores) from eastern North America. A low-abundance, low-diversity cryptospore assemblage containing specimens of Pseudodyadospora, Velatitetras, and alete monads has been recovered from the Velleda Member of the Ellis Bay Formation (Upper Ordovician, Hirnantian). The Gun River Formation (Lower Silurian, Aeronian) contains a low-abundance, low-diversity assemblage composed of specimens of Velatitetras, Laevolcancis, and alete monads. The occurrence of these assemblages provides evidence for early land plants in this part of North America during the Late Ordovician and Early Silurian, and documents the existence of a terrestrial-based flora during and after the Saharan (Late Ordovician) glaciation.

Distribution of the middorsal stripe dimorphism in the wood frog, Rana sylvatica, in eastern North America

1980 ◽  
Vol 58 (9) ◽  
pp. 1643-1651 ◽  
Author(s):  
Frederick W. Schueler ◽  
Francis R. Cook
Keyword(s):  
United States ◽  
North America ◽  
Rana Sylvatica ◽  
Wood Frog ◽  
Eastern North America ◽  
Hudson Bay ◽  
Northeastern United States ◽  
Southern Ontario ◽  
Maritime Canada ◽  
Eurasian Species

The frequency of the middorsally striped morph of Rana sylvatica in Ontario and Manitoba varies from absence in southern Ontario to 80% on the coast of Hudson Bay, with a general value of 20–30% in the boreal forest, a rise to 50% on the forest–grassland ecotone in southern Manitoba, and a decline westward to 20% on the edge of the prairies. This morph is rare in the northeastern United States and Maritime Canada. The suggested relationship between its frequency and the "grassiness" of the background on which predators view it is reexamined, and it is suggested that a linkage with earlier transformation as demonstrated in Eurasian species may explain certain anomalies.

Present and postglacial rates of uplift for glaciated northern and eastern North America derived from postglacial uplift curves

1970 ◽  
Vol 7 (2) ◽  
pp. 703-715 ◽  
Author(s):  
J. T. Andrews
Keyword(s):  
North America ◽  
Eastern North America ◽  
Hudson Bay ◽  
High Cell ◽  
Uplift Rate ◽  
Radiocarbon Dates ◽  
Marine Deposits ◽  
Maximum Value ◽  
Current Maximum ◽  
A Current

Average rates of postglacial uplift reach a maximum value of nearly 4 m 100 y−1 over southeastern Hudson Bay, and another high cell, with rates of about 2.5 m 100 y−1, lies between Bathurst Inlet and Southampton Island. Current rates of uplift are underestimated if exponential curves are fitted solely to dated raised marine deposits without considering the amount of future recovery. Rates of rebound are, instead, derived from A/t where A is uplift in the first 1000 y since deglaciation, and t is time since deglaciation. For the northwest margin of the former ice sheet coefficients of determination for rate of uplift, at specific times, as a function of distance are [Formula: see text]. Maps of rates of uplift for northern and eastern North America are presented for 8000 y B.P., 6000 y B.P. and the present day. They reveal the existence of three uplift centers and show that rates of uplift declined from a maximum of 10 to 12 m 100 y−1, immediately following deglaciation, to a current maximum of about 1.3 m 100 y−1. Agreement is satisfactory when calculated rates of uplift are compared with those derived from geological observations, radiocarbon dates, and from water-level records. A final map shows isochrones on the uplift rate of ~1 m 100 y−1. The rate dropped to this value about 10 000 y ago on the outer northwest and southeast coasts, whereas the value might not be reached for another 2000 y in southeastern Hudson Bay.

Revalidation of the milliped genus Amplaria Chamberlin 1941 (Diplopoda,  Chordeumatida, Striariidae), and description of two new species from caves in Sequoia and Kings Canyon National Parks, California

Zootaxa ◽  
2007 ◽  
Vol 1532 (1) ◽  
pp. 23-39 ◽  
Author(s):  
WILLIAM A. SHEAR ◽  
JEAN K. KREJCA
Keyword(s):  
New Species ◽  
North America ◽  
National Parks ◽  
Type Species ◽  
Washington State ◽  
Eastern North America ◽  
The Pacific ◽  
Two New Species ◽  
Phyletic Line

The milliped genus Amplaria Chamberlin 1941 was synonymized with Striaria Bollman 1888 by Hoffman (1980). Examination of a much wider range of materials of nominal Striaria species both from eastern North America and the Pacific coastal states shows that some species occurring from California to Washington (state) represent a distinct phyletic line, for which Amplaria Chamberlin 1941 is the oldest available generic name. Speostriaria Causey 1960 is a synonym of Amplaria. Amplaria muiri n. sp. and A. adamsi n. sp. are two new, recently discovered species from caves in Sequoia and Kings Canyon National Parks, California. Illustrations are provided of a specimen that may represent the type species, Amplaria eutypa (Chamberlin) 1953.

North American biogeography and taxonomy of Cryptolithus (Trilobita, Ordovician)

1994 ◽  
Vol 68 (4) ◽  
pp. 808-823 ◽  
Author(s):  
Frederick C. Shaw ◽  
Pierre J. Lespérance
Keyword(s):  
North America ◽  
North American ◽  
Type Species ◽  
Time Span ◽  
Eastern North America ◽  
Evolutionary Mechanisms ◽  
Variable Character

Museum and field restudy of Cryptolithus from all known geographic and stratigraphic occurrences in eastern North America shows that the principal variable character in this genus is the number of fringe pit arcs. Because this character varies within populations and even single individuals, it cannot be used to distinguish the earlier, typologically defined species of the genus. Instead, a neotype is designated here for the type species, Cryptolithus tessellatus Green, 1832, and morph designations are used for all pit arc variants. Over the time span considered, the species increased the number of pit arcs, but the ecological and evolutionary mechanisms responsible cannot be identified with certainty.

A revision of the genus Orchestia Leach, 1814 with the reinstatement of O. inaequalipes (K.H. Barnard, 1951), the designation of a neotype for Orchestia gammarellus (Pallas, 1776) and the description of three new species (Crustacea: Amphipoda: Talitridae: Talitrinae)

Zootaxa ◽  
2020 ◽  
Vol 4808 (2) ◽  
pp. 201-250
Author(s):  
ALAN A. MYERS ◽  
JAMES K. LOWRY
Keyword(s):  
New Species ◽  
North America ◽  
South America ◽  
Type Species ◽  
Pacific Coast ◽  
Species Group ◽  
Eastern North America ◽  
The Pacific ◽  
North Eastern ◽  
Three New Species

The amphipod genus Orchestia is revised. It now includes 10 species of which three are new: O. forchuensis sp. nov. from north-eastern North America and Iceland., O. perezi sp. nov. from Chile and O. tabladoi sp. nov. from Argentina. Orchestia inaequalipes (K.H. Barnard 1951) is reinstated. The type species of the genus, O. gammarellus is redescribed based on material from Fountainstown, Ireland and a neotype is established to stabilize the species. The species was originally described from a garden in Leiden, far from the sea. Its true identity is unknown and no type material exists. Orchestia gammarellus (Pallas, 1776) is shown to be a sibling species group with members in both hemispheres of the temperate Atlantic as well along the Pacific coast of South America. A hypothesis for the establishment of the current distribution of Orchestia species is presented that extends back to the Cretaceous. 

Proconchidium from Late Ordovician strata of Brodeur Peninsula, Baffin Island, Arctic Canada

1989 ◽  
Vol 63 (1) ◽  
pp. 25-33 ◽  
Author(s):  
Rong Jia-Yu ◽  
Brian Jones ◽  
F. W. Nentwich
Keyword(s):  
North America ◽  
Late Ordovician ◽  
Baffin Island ◽  
Arctic Canada ◽  
Internal Structures ◽  
Biogeographic Provinces ◽  
Recorded Occurrence

Proconchidium brodeurensis n. sp. occurs 212 m above the base of member B of the Baillarge Formation on Brodeur Peninsula, Baffin Island, 8 m below the Ordovician–Silurian boundary. Study of Proconchidium shows that it can be easily distinguished from Eoconchidium but possesses many characters that are similar to those in Tcherskidium. Analysis of internal structures suggests that the three genera can be distinguished from each other and belong to Virgianidae. Tcherskidiidae is a synonym of Virgianidae and should be abandoned.This represents the first recorded occurrence of Proconchidium in North America. Although this genus and its related genera Tcherskidium Sapelnikov, 1972, and Eoconchidium Rozman, 1967, are common in Ashgill strata of Eurasia, they have not been recorded or illustrated from North America. This led to the suggestion that distinct brachiopod biogeographic provinces may have existed during the Ashgill. The occurrence of these genera probably indicates that they may have lived in mostly tropical and subtropical zones.

The Churchill kimberlite field, Nunavut, Canada: petrography, mineral chemistry, and geochronology

2008 ◽  
Vol 45 (9) ◽  
pp. 1039-1059 ◽  
Author(s):  
S. E. Zurevinski ◽  
L. M. Heaman ◽  
R. A. Creaser ◽  
P. Strand
Keyword(s):  
North America ◽  
Mantle Plume ◽  
Electron Microprobe ◽  
Mineral Chemistry ◽  
Eastern North America ◽  
Hudson Bay ◽  
Continental Extension ◽  
Group I ◽  
Hypabyssal Kimberlite ◽  
Kimberlite Field

Seventy-nine kimberlite intrusions have been identified in the Churchill Province, Nunavut, the result of an aggressive diamond exploration program by Shear Minerals Ltd. and their partners. This is one of Canada’s newest and largest kimberlite districts, situated immediately west of Hudson Bay between the communities of Rankin Inlet and Chesterfield Inlet. This study documents the occurrence of bonafide kimberlite rocks, classified as mainly sparsely macrocrystic, oxide-rich calcite evolved hypabyssal kimberlite and macrocrystic oxide-rich monticellite phlogopite hypabyssal kimberlite. Electron microprobe analyses of olivine, phlogopite, spinel, and perovskite support this petrographical classification. Low 87Sr/86Sr isotopic compositions determined from perovskite indicate a group I affinity. In addition, 27 precise U–Pb perovskite and Rb–Sr phlogopite emplacement ages have been determined for the Churchill kimberlites, indicating that magmatism spans ∼45 million years (225–170 Ma). The Churchill kimberlites belong to the NW–SE-trending corridor of Jurassic–Triassic kimberlite magmatism in eastern North America, which includes the Kirkland Lake, Timiskaming, and Attawapiskat kimberlite fields. Churchill kimberlites extend this corridor ∼800 km northwest, suggesting that the corridor may continue northwest with older kimberlites. This corridor is interpreted as the continental expression of magmatism linked to either a single or multiple mantle-plume hotspot track(s), a pattern geographically coincident with independent estimates for the timing and location of the continental extension of both the Great Meteor and Verde hotspot tracks.

Designation of a neotype and paraneotype for Conularina triangulata (Raymond, 1905) (Upper Ordovician, eastern North America)

2020 ◽  
Vol 94 (4) ◽  
pp. 796-797
Author(s):  
Heyo Van Iten ◽  
Mario E. Cournoyer ◽  
Michelle Coyne
Keyword(s):  
New York ◽  
North America ◽  
Late Ordovician ◽  
Quebec City ◽  
Eastern North America ◽  
Upper Ordovician ◽  
Thrust Sheet ◽  
City Formation ◽  
Early Late

Conularina triangulata (Raymond, 1905), the genotype of Conularina Sinclair, 1942, is a rare, early Late Ordovician conulariid (Cnidaria, Scyphozoa; Van Iten et al., 2006) having three sides or faces instead of four (Sinclair, 1942, fig. 9; Van Iten, 1992, text-fig. 3E). Originally described from the Valcour Formation (early Sandbian; Dix et al., 2013) on Valcour Island, New York (Sinclair, 1942), C. triangulata has since been found in laterally equivalent strata of the upper Laval Formation (‘Upper Chazy’; Sinclair, 1942) in Laval, Québec, Canada (Sinclair, 1942). From this same unit and area, Sinclair (1942) erected three new, four-sided species of Conularina (C. irrasa, C. raymondi, and C. undosa), and he erected a single four-sided species (C. narrawayi) from the Ottawa Formation (now the Sandbian–Katian Ottawa Group; Dix et al., 2013) at Tétreauville (now Gatineau), Québec. Subsequently, Jerre (1994) reported the occurrence of two species of Conularina in the Upper Ordovician of Sweden. Jerre (1994) also proposed that Eoconularia? forensis Sinclair, 1946 from the Upper Ordovician Citadelle Formation (‘Quebec City’ Formation; Sinclair, 1946) in Québec City, Québec (Promontoire de Québec thrust sheet, Appalachian Humber Zone, Allochtonous Domain; Castonguay et al., 2002) is a species of Conularina.

scholarly journals The Grinnell and Terra Nivea Ice Caps, Baffin Island

1956 ◽  
Vol 2 (19) ◽  
pp. 653-656 ◽  
Author(s):  
J. H. Mercer
Keyword(s):  
North America ◽  
Equilibrium Line ◽  
Eastern North America ◽  
General Tendency ◽  
Baffin Island ◽  
Ice Caps ◽  
Ice Cap ◽  
The North

AbstractThe Grinnell and Terra Nivea Ice Caps are the southernmost in eastern North America. The Grinnell Ice Cap reaches an altitude of 870 m. (2854 ft.). The general tendency is for slight retreat, but one large glacier is advancing. The equilibrium line is considerably lower than on the Penny Ice Cap to the north. Both firn and superimposed ice are important in the economy.

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