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A Darriwilian (late Middle Ordovician) brachiopod fauna from the Lower Formation of the Chiatsun Group at Jiacun, northern Nyalam, southern Tibet, consists of ten brachiopod species, forming a distinct Aporthophyla- Paralenorthis Association. Its taxonomic composition is typical of the Aporthophyla Fauna that occupied lower BA2 to upper BA3 benthic environments on sandy lime mud substrates. The occurrence of Paralenorthis in southern Tibet is confirmed for the first time, represented by P. costata sp. nov. Numerical analyses ( PCA and CA) of 18 Darriwilian brachiopod faunas from ten palaeoplates or terranes indicate that: (1) the Aporthophyla Fauna was confined to a specific latitudinal belt although it had a wide lateral distribution from the large palaeocontinents of Gondwana to Laurentia; (2) the Saucrorthis Fauna, a typical late Middle Ordovician regional fauna, is limited to a much smaller area, marginal to the Gondwana supercontinent; (3) the strong provincialism persistent in the late Middle Ordovician contributed to increased gamma biodiversity during the Great Ordovician Biodiversification Event. [ABSTRACT FROM AUTHOR]

Multivariate analysis based on nine biometric characters of 171 Late Ordovician rhynchonellide specimens from nine upper Sandbian-upper Katian localities in North America supports the hypothesis that one of the diagnostic taxa of the North American epicontinental brachiopod fauna, Hiscobeccus, evolved from Rhynchotrema, which lived predominantly in peri-cratonic settings. The oldest known Hiscobeccus, H. mackenziensis of early Katian age, exhibits transitional characteristics between Rhynchotrema and Hiscobeccus, and it clusters more closely with Rhynchotrema than with younger species of Hiscobeccus of mid-late Katian (Maysvillian-Richmondian) age. Diversification of the Hiscobeccus lineage in epicontinental seas was characterized by drastic increase in shell size, globosity and lamellosity, especially in palaeoequatorially located inland basins. Such morphological trends are interpreted as adaptation to relatively shallow, muddy substrates, moderate water turbulence, relatively low oxygen content and unstable supply of nutrients in generally overheated epicontinental seas with sluggish circulation. [ABSTRACT FROM AUTHOR]

Abstract: Massive-bedded Thalassinoides ichnofacies occurs pervasively in widely separated areas on the vast Upper Ordovician carbonate platforms along the palaeoequator of Laurentia, from the Børglum River Formation in North Greenland, through the Red River Formation and Bighorn Dolomite of the Williston Basin (Manitoba, Canada to Wyoming, USA), to the Ely Springs Dolomite and equivalent strata of the eastern Great Basin (Utah and Nevada, USA). The Late Ordovician Thalassinoides is characterised by complex, three-dimensional, anastomosing or multi-level galleries that are consistent in size, pattern and density, with preserved depth of 1m or greater. In addition to the similar Thalassinoides burrows, the ichnofacies across the palaeocontinent also contains typical taxa of the Red River biota, such as the soccer-ball sized receptaculitid Fisherites, large-shelled, diverse and abundant nautiloids, the distinctively planispiral gastropod Maclurina, as well as diverse tabulate and rugose corals. The consistent characteristics of the Red River biofacies and Thalassinoides ichnofacies suggest a palaeogeographically homogeneous and temporally stable depositional environment along the palaeoequatorial belt of Laurentia during the pre-Hirnatian Late Ordovician. The Thalassinoides ichnofacies marked the first phase of mega-scale invasion of burrowers into relatively deep-water platform and shelf environments by successively creating a well-oxygenated deep burrow system for protection and deposit feeding. Such substrate tiering expansion constituted an important aspect of the Great Ordovician Biodiversification Event. [Copyright &y& Elsevier]

Brachiopods from the lower Tonggao Formation (Floian, late Early Ordovician) of Sandu, southeastern Guizhou Province, represent a deep-water benthic shelly fauna from the Jiangnan Slope facies of the South China paleoplate. The fauna contains 16 brachiopod taxa, with orthides, lingulates, and pentamerides being the common groups. Concurrent graptolites confine the brachiopod fauna to the Tetragraptus approximatus and the Acrograptus filiformis biozones (early Floian). The first appearance datum (FAD) of several brachiopod genera, such as Paralenorthis, Protoskenidioides, and Nereidella, in the Sandu slope facies is one or two graptolitic biozones lower than their FAD in shallower water facies on the Yangtze Platform. Later in the late Floian, these genera became major components of the Sinorthis fauna that flourished over much of the Yangtze Platform, suggesting a migration of the benthic shelly fauna from slope to platform facies during the Floian radiation in South China. Compared to the platform fauna, the deep-water brachiopod fauna of the Sandu area has a lower level of richness, diversity, and community organization. Three brachiopod associations are recognized: the Paralenorthis–Nereidella, the Palaeoglossa longa, and the Lingulella–Protoskenidioides associations. An upsection decrease in shell size, faunal richness, and species diversity in the Tonggao Formation indicate a deteriorating environment towards hypersalinity in the Sandu area, resulting in the ultimate disappearance of the deep-water brachiopod fauna. [ABSTRACT FROM AUTHOR]

Abstract: The Ordovician radiation is the earliest and most important biodiversification event in the evolution of the Paleozoic Evolutionary Fauna (PEF), when the basic framework of PEF was established. The radiation underwent a gradual, protracted process spanning more than 40 million years and was marked by several diversity maxima of the PEF. Case studies conducted on the Upper Yangtze Platform (South China Palaeoplate) showed that the Ordovician radiation was characterized by drastic increases in α- and β-diversity in various groups of organisms. During the radiation, brachiopods, trilobites, and graptolites of the PEF became more diverse to dominate over the Cambrian Evolutionary Fauna (CEF) in all marine environments. At either global or regional scales, however, the Ordovician radiation was highly heterogeneous in time and space, and the rate and pattern of radiation exhibited by different major fossil groups were also variable. [Copyright &y& Elsevier]

Systematic and statistical study of brachiopods from the Dawan Formation of the Yichang area, western Hubei Province, central China, indicates that, at generic and specific levels, the α diversity of Early to Mid Ordovician brachiopods in the study area reached the first acme at the beginning of the Corymbograptus deflexus Biozone, marked by the diverse Sinorthis typica Community. This diversity maximum of brachiopods occurred approximately one biozone later than that of the Upper Yangtze Platform. In taxonomic constituents, the main contributors to the diversity maximum were orthoids, which experienced a major increase in the number of genera in the upper Didymograptellus eobifidus Biozone and the lower C. deflexus Biozone. In brachiopod communities or associations, orthoids and pentameroids were the dominant elements. Analyses of Early–Mid Ordovician brachiopods from the Upper Yangtze Platform indicate that a high level of brachiopod community organization, with temporal and spatial stability, was achieved by the Sinorthis Community, which persisted from the D. eobifidus to the Azygograptus suecicus biozones (early Arenig). In the D. eobifidus Biozone, the Sinorthis Community thrived across a wide ecological range (BA3 to upper BA4) in the siliciclastic facies of the central part of the Upper Yangtze Platform and, by the latest D. eobifidus interval, invaded more carbonate-rich substrates in more offshore settings in the northeastern part of the platform (the present Yichang area). [ABSTRACT FROM AUTHOR]