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Ziegler's (1965) early Silurian brachiopod community zones and Boucot's (1975) Benthic Assemblages have been instrumental in determining the community structures of early–middle Paleozoic level-bottom communities, but are difficult to apply to reef ecosystems due to the mixing of level-bottom community assemblages in these systems. In this study, Shannon and Simpson diversity levels were calculated for reef-dwelling brachiopod faunas from several North American and one European localities. Reef-dwelling brachiopod diversity collapsed at the end of the Ordovician and did not recover until the mid-Aeronian when modest diversity reef faunas appeared in the higher tropics. Reef-dwelling brachiopods did not achieve high diversity levels until the Telychian when reefs invaded the paleoequatorially located Hudson Bay and Moose River basins. The Attawapiskat Formation (Telychian) contains the earliest known coral-stromatoporoid reef complex with associated high-diversity brachiopod faunas. These faunas were separated into nine community associations through clustering and principal component analyses. These associations can be further grouped into a level-bottom-type and a cryptic-type based on dominant brachiopod taxa, diversity levels, average shell size, and substrate type. Surprisingly, the large species Pentameroides septentrionalis was able to thrive in the relatively flat and open spaces of inter-reef areas and among frame-building corals and stromatoporoids within reef cores. The absence of Stricklandia within the Attawapiskat Formation is due to the high water temperature of the equatorial seas which were too warm to be invaded by this cool-water dependent genus. In addition, the presence of deep-water Clorinda and Gypidula in the shallow-water Attawapiskat reefs is explained by the lack of hurricane-grade storms in the equatorial region, which would be comparable to the quiet-water conditions below storm wave base in higher latitudes. [ABSTRACT FROM AUTHOR]

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Abstract: Brachiopod communities have been widely used for palaeoecological studies and reconstruction of sea-level changes in Earth history. Previous studies of brachiopod communities emphasised sampling benthic shelly fossils preserved in situ to avoid preservation bias. Silurian (Wenlock) brachiopod assemblages are well preserved as debris-turbidity flows, including calcareous concretions, embedded in thick sequences of black shale of the Cape Phillips Formation, with a mixture of deep-water brachiopods and transported shallow-water forms. In this study, the first attempt is made to use the transported assemblages to reconstruct Silurian brachiopod communities that once lived along a palaeogradient from the shallow-water Arctic Platform to the deep-water Franklinian Basin. Seven transported brachiopod assemblages were recognised using multivariate analyses (cluster analysis and principal components analysis), with varying ratios of shallow- versus deep-water shells, segregated according to their known palaeobathymetric ranges in other regions. The Wenlock–early Ludlow sea-level fluctuations in the study area, reconstructed using the percentage values of shallow- and deep-water brachiopod specimens as a proxy, have a high degree of agreement with the Arctic Silurian sea-level curve and moderate agreements with global sea-level histories of other regions such as the British Isles and Gotland interpreted from graptolite abundance and diversity changes, and sequence and event stratigraphical methods, respectively. [Copyright &y& Elsevier]

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Four species of olenelloid trilobites characterized by advanced or robust genal spines are described from the lower Cambrian Rabbit Point Formation (Cambrian Series 2, Stage 4) of eastern Devon Island, representing the most diverse assemblage of olenelloids yet described from Arctic Canada. New taxa: n. sp., n. sp., n. gen. and n. sp. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Earth Sciences is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Stegerhynchus was perhaps the most common rhynchonellide brachiopod in the Early Silurian (Llandovery) postextinction brachiopod fauna of North America. In shell morphology, it closely resembles the Late Ordovician rhynchonellide Rhynchotrema in having a rostrate shell posterior and simple, strong costae. It differs internally from Rhynchotrema primarily in having a much-reduced septalium (=cruralium). Superficially Stegerhynchus has a conservative, typically simple, rhynchonellide morphology, but detailed biometric analysis of large samples from the >400 m-thick Llandovery (mid-Aeronian to mid-Telychian) tropical carbonate succession of Anticosti Island reveals that the genus underwent significant evolutionary and ecophenotypic changes over about five million years. The shell length/width ratios of Stegerhynchus peneborealis from sediments of a low-energy, muddy substrate tend to be lower than those of S. deltolingulatus new species from high-energy, reef or inter-reef settings. A wider shell and hingeline probably had a greater stability on the soft seafloor. Also a wider shell appears to be associated with a larger (relative to shell size) sulcus size at the anterior margin. The changes in relative sulcus size either represent ecophenotypic variation in response to environmental conditions, or a random effect of evolutionary selection through time. Both multivariate and single-character analyses demonstrate that two important biometric features, the apical angle and shell flank rib number, separate all forms of Anticosti Island Stegerhynchus (middle Aeronian to middle Telychian) from the widely cited European species Stegerhynchus borealis (latest Telychian-Wenlock) from the type area of Gotland, Sweden. The temporal changes of these two characters are interpreted to be evolutionary modifications. [ABSTRACT FROM AUTHOR]