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An unusually rich and diverse suite of virgianid brachiopods, hitherto poorly known, is systematically described here for the first time from the Ordovician–Silurian boundary interval (late Katian – Aeronian) of North Greenland. The Late Ordovician virgianids comprise typical taxa of the warm‐water Tcherskidium fauna (e.g. Tcherskidium tenuicostatum, Proconchidium schleyi, Holorhynchus giganteus and Deloprosopus dawesi sp. nov.). Among the early Silurian taxa, Virgiana hursti sp. nov. occurs as abundant shell beds, similar to other congeneric species in Laurentia, but has somewhat larger internal skeletal structures, albeit not as extravagantly developed as in the late Katian virgianids; Borealoides balderi gen. et sp. nov. shows extreme thickening of the shell wall and internal structures, approaching the extravagant calcification of Katian virgianids. The highly distinctive mid‐Aeronian stricklandioid brachiopod genus, Kulumbella, characterized by a shell with criss‐cross (divaricate) ribbing, also occurs in North Greenland, represented by K. heimdali sp. nov., which has the largest and most strongly biconvex shells for the genus. Palaeogeographically, the Late Ordovician virgianid fauna of Laurentia was highly distinct, confined to the low–mid tropical latitudes north of the palaeoequator. In comparison, the early Silurian (Rhuddanian) Virgiana and some related taxa in Laurentia spanned the tropics of both hemispheres, forming extensive shell beds in carbonate basins, although Borealis and Borealoides gen. nov. remained confined largely to the northern hemisphere, suggesting a certain level of provincialism extending into the earliest Silurian. A palaeoecological preference for warm‐water carbonate settings would explain the unusual abundance and richness of the virgianid faunas in North Greenland. [ABSTRACT FROM AUTHOR]

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]

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.)

Abstract: The early Katian (Late Ordovician) was marked by a major greenhouse episode and the early stage of a first-order marine transgression that led to the flooding of much of North America during the middle–late Katian. Multivariate analyses of 33 brachiopod faunas of early Katian (Trentonian, Chatfieldian, late Caradoc) age, including 252 rhynchonelliform genera, demonstrate that the “Trentonian brachiopod faunas” of Laurentia were already clearly differentiated into a Scoto-Appalachian fauna and an epicontinental fauna. Globally, four distinct faunal clusters are identified: Kazakhstan, Avalonia, epicontinental Laurentia, and Scoto-Appalachia. The Scoto-Appalachian fauna, which originated during the Sandbian, persisted into the early Katian and became most closely related to the brachiopod faunas along the western margins of Laurentia. The early Katian epicontinental faunas of Laurentia were more closely related to the coeval brachiopods of the Lithuanian–North Estonian confacies belts of Baltica than to the Scoto-Appalachian fauna. Palaeoecological control on the faunal endemism within Laurentia was attributable to isolation of Appalachian foreland basin by faulting and peripheral bulging during the early Taconic Orogeny, palaeolatitudinal faunal gradient from the subtropical Appalachia to mid-tropical epicontinental Laurentia, as well as different water depth, water temperature, and substrate types between the two palaeogeographical settings of Laurentia. [Copyright &y& Elsevier]

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.)

Examination of topotype material of the type species of Dalmanella, D. testudinaria, from the Hirnantian strata of Borenshult, southern Sweden, revealed several diagnostic characters that distinguish the type species from some common North American species assigned previously to the genus. The typical Dalmanella testudinaria has a consistently developed, primary medial interspace in the dorsal valve, a cardinal process with an invariably bilobed myophore, punctae of two distinctly different sizes, and a lack of aditicules. In contrast, many Late Ordovician species from North America, such as 'Dalmanella' meeki and 'Dalmanella' multisecta from the Cincinnati type area, consistently have a dorsal medial costa, with a strong tendency to develop aditicules and a trilobate cardinal process. This study confirms the previous notion of many authors that true Dalmanella testudinaria, or the genus as a whole, is either rare or entirely absent in North America. Typical Dalmanella was predominant in cool-water depositional environments (such as the Hirnantia Fauna), whereas the North American dalmanellids (e.g. Cincinnati-type 'Dalmanella', Paucicrura, and Diceromyonia) were most abundant and diverse in tropical, epicontinental sea settings. A clear definition of the true Dalmanella, therefore, has important implications for the study of Late Ordovician-Early Silurian brachiopod evolution, paleoecology, and paleobiogeography. [ABSTRACT FROM AUTHOR]

Despite the crucial role of epibenthic primary producers (cyanobacteria, green and red algae), no diversity curves for calcimicrobes and calcareous algae are available to assess the pyramiding paleoecology characterizing the Ordovician biodiversification episode. A total of 24 taxa of calcimicrobes and calcareous algae are identified from a Dapingian to lower Katian succession of carbonate sedimentary rocks exposed at the Leyayilitag ridge, Bachu Uplift, Tarim Basin, northwest China. Calcimicrobes (14 taxa), Dasycladales (seven taxa), Bryopsidales (one taxon), and Cyclocrinales (two taxa) contribute to five distinct taphocoenoses characterizing a suite of carbonate mounds. In stratigraphic order, these are calathid sponge mounds, algal calcimicrobial mounds, algal mounds, algal reefs, and calcimicrobial mounds. Within the lower Katian Belodina confluens Zone, the diversity increases substantially from around 5 to more than 20 taxa per 2 Ma. This increase in diversity is based on new calcimicrobes ( Bija, Ortonella, Garwoodia, Hedstroemia, Rothpletzella, Phacelophyton, Rauserina) and the diversification of Dasycladales and Cyclocrinales. By comparison, the global diversity of calcimicrobes and calcareous algae (derived from literature data) started to increase earlier, namely within the late Darriwilian Pygodus serra Zone (offset of about 4 Ma). This offset might be due to the peculiar lithology of the Sandbian Tumuxiuke Formation (condensed section of red nodular limestones bounded by disconformities). However, a similar temporal offset is recorded for calathid sponge mounds; therefore, the Tarim tectonic microplate (Tarim Block) might display an endemic-anachronistic character. The diversity curves of Ordovician benthic primary producers (calcimicrobes, calcareous algae) are similar to those recorded by some fossil groups, in particular eleutherozoan echinoderms. [ABSTRACT FROM AUTHOR]

A recovery brachiopod fauna occurs in the lower Niuchang Formation (upper Rhuddanian - lower Aeronian, Llandovery) of the Xinglongchang section, Meitan County, northern Guizhou Province, South China. Nine collections were made at the section, all of which are dominated by brachiopods, and three associations are recognized here and their paleoecology is discussed. Paleoenvironmental analysis shows a shallowing upward trend for the lower Niuchang Formation, although a global transgression was happening at that time. The balance between the global transgression and the regional Qianzhong Uplift guaranteed a stable environment for the formation of the Niuchang Formation and the recovery of brachiopods in South China after the end-Ordovician mass extinction. In addition to the traditional methods of principal component analysis and cluster analysis, a relatively new technique to paleontology, 'network analysis', is applied successfully in this study. It is suggested that network analysis could be used as one of the supporting methods in investigating brachiopod paleoecology. [ABSTRACT FROM AUTHOR]