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This is the first record of Cornulites sp. as an epibiont on brachiopods from the middle Ashgill, Late Ordovician, of the South China Palaeoplate. Twenty-one cornulitid specimens were found attached to the brachiopod shells of Altaethyrella zhejiangensis and Ovalospira dichotoma. Both the location of cornulitids and their orientation on the brachiopod shells indicate a possible commensal relationship between the cornulitids and their hosts.

Seventeen trilobite species belonging to 16 genera and 13 families are systematically documented from the Houping Formation (upper Dapingian-lower Darriwilian, Middle Ordovician) at the Datangkou and Dacao sections, Chengkou, northern Chongqing. Of these, a new species, Mioptychopyge chengkouensis sp. nov., is established and described. New morphological information is provided for previously known species on the basis of new specimens. Two trilobite associations based on faunal composition and dominant forms are distinguished from the Houping Formation, in ascending order, the Agerina Association (from the lower and middle members) and the Nileus-Illaenus Association (from the upper member). The Agerina Association lived in an inner shelf margin environment with carbonate substrate above storm wave base (<70 m deep), whereas the Nileus-Illaenus Association developed in a shallow outer shelf environment below storm wave base (>70 m deep), indicating a rise of relative sea level corresponding to the early Darriwilian transgression. The cluster and nonmetric multidimensional scaling analyses of the trilobites in the formation show that the fauna had a strong endemicity to South China and a close biogeographic connection with east Peri-Gondwana, especially Tarim, Annamia and central Iran. [ABSTRACT FROM AUTHOR]

The richly fossiliferous succession of the Wulipo Formation in the Huangjiaba area near Meitan in northern Guizhou, SW China, represents one of the very rare records of shelly fauna across the Ordovician and Silurian transition worldwide. This area is therefore crucial for understanding the pattern and dynamics of the end‐Ordovician mass extinction (EOME). Historically, the Wulipo Formation was dated as middle Rhuddanian (early Silurian). However, its fauna shows a close affinity with Transitional Benthic Fauna 3 (TBF 3), now known to be confined within the late Hirnantian (latest Ordovician) in well‐constrained successions globally. Here we present for the first time, chemostratigraphic data from the Wulipo Formation which confirm the presence of the Hirnantian Isotope Carbon Excursion. A critical review of faunal evidence further indicates a late Hirnantian age for this formation, and thus the hitherto only known anomalous TBF 3 record documented from South China is convincingly redated. The important implication is that the substantial biotic recovery after the EOME commenced globally at the very beginning of the Silurian with an overall amelioration of physical conditions. The new findings also suggest a much wider distribution of postglacial warm‐water benthic faunas on the Yangtze Platform during the late Hirnantian than previously envisaged. [ABSTRACT FROM AUTHOR]

Richly fossiliferous Hirnantian shelly strata of near‐shore facies in northern Guizhou, South China, known as the Kuanyinchiao Formation, superbly record glacioeustatic sea‐level fluctuations and benthic faunal turnover. Recent studies of the temporal and spatial distribution of these carbonates and shelly fossils permit a critical stratigraphic revision and establishment of a robust regional stratigraphic correlation. The formation is revised to include three informal subdivisions, that is, units A, B, and C, in ascending order. Unit B of the formation typically is dominated by peloidal or oolitic grainstones, and unit C is composed of skeletal wackestone and calcareous mudstone, both units sharing distinctive coral and brachiopod faunas. This contrasts sharply with unit A of the formation, consisting of mudstone, silty mudstone, or calcareous mudstone, that yields the cool‐water Hirnantia fauna and associated coral fauna. In view of the presence of carbonate ooids and peloids, rugose corals, and a distinctive brachiopod assemblage, all indicative of warm‐water conditions, unit B, as well as unit C yielding the same shelly fauna, is interpreted as representing postglacial sedimentation immediately following the major Hirnantian glaciation, thus marking a significant climatic shift. Similar warm‐water carbonate rocks have been recognized in a number of regions along the margin of the Qianzhong Oldland, including Bijie, Renhuai, Tongzi, and Fenggang of northern Guizhou. Such a vast distribution area of these rocks indicates that postglacial carbonates are more widespread on the Yangtze Platform of South China than previously thought, providing a rare window into rocks and fossils of the survival interval immediately following the extinction event associated with the Hirnantian glacial episodes. [ABSTRACT FROM AUTHOR]

The decimeter-scale 3-D network structure of the Upper Ordovician Pagoda Formation in South China has been an enigmatic sedimentary feature and a case of non-uniformitarian carbonate depositional system, without modern analog. The network bands are developed pervasively throughout the entire Pagoda Formation, superficially resembling desiccation or syneresis cracks, especially in bedding-plane view, with decimeter-scale sub-polygonal to irregularly sinuous patterns. Detailed petrographic analysis, however, shows that the crack-like network bands have the same carbonate matrix, skeletal grains, and overall fabrics as the rock they surround. In this study, we demonstrate that the network structure is not generated by shrinkage cracks but is rather a time-specific lithofacies. It originated from prolonged growth of nodular carbonate, controlled by the convergence of several geological and paleoclimatic factors, including a) a protracted sea-level highstand lasting for about 5 Myr, b) an interval of tectonic quiescence favoring the dominance of carbonate production, with minimal siliciclastic input, and c) location of the South China paleoplate in the hurricane-free paleoequatorial zone devoid of severe storm disturbances between the fairweather and maximum storm wave bases (normally 15–120 m depths), favoring long-term, uninterrupted growth of CaCO 3 meganodules on a mid-shelf substrate. This study corroborates recent paleogeographic reconstructions that position the South China paleoplate on the Equator during the Late Ordovician. [ABSTRACT FROM AUTHOR]

Latest Ordovician and earliest Silurian tabulate corals of the South China paleoplate are summarized at the generic level. In contrast to the abundant late Katian records, there is no record of tabulate corals in the early–middle Hirnantian rocks in South China, lithostratigraphically represented by the Kuanyinchiao Formation and its equivalents. The tabulate fauna from the late Hirnantian and the earliest Silurian rocks of South China is characterized by the occurrence of three cosmopolitan genera:Paleofavosites,ProporaandHalysites. They differ morphologically from the pre-Hirnantian tabulate corals of South China. Such a long-ranging and low-diversity tabulate coral fauna also indicates a warm but somewhat unfavorable living environment during the survival interval after the second pulse of the end-Ordovician mass extinction. [ABSTRACT FROM AUTHOR]

Re-examination of newly collected topotype material confirms that the type species of Yangtzeella, Y.  poloi, a widespread Early and Mid Ordovician syntrophiidine brachiopod in South China, has a finely costellate shell rather than being smooth as previously thought. Thus, the subgenus Yangtzeella ( Vadimella) Nikitina et  al., established on the basis of fine costellae, is invalidated. Among 15 species of Yangtzeella, five species are recognized as valid based on multivariate analyses: Y.  poloi, Y.  unsulcata, Y.  songziensis, Y.  kueiyangensis and Y.  igori, among which the type species was the oldest known. Six are synonymized: Y.  septata, Y.  reticulata, Y.  lensiformis, Y.  depressa, Y.  yichangensis and Y.  minuta. Four are rejected from Yangtzeella: Y.  extensa, Y.  similior, Y.  yohi and Y.  poloi var. minor. Regional biostratigraphy indicates that Yangtzeella first appeared in a relatively deep-water setting on the Lower Yangtze Platform (South China palaeoplate) during late Tremadoc time ( Scolopodus warendensis conodont biozone) and then expanded to the deeper Jiangnan Slope as well as to the shallower Upper Yangtze Platform. The genus experienced two episodes of heightened abundance and diversity on the Upper Yangtze Platform during late Dapingian and mid Darriwilian times, respectively. Outside South China, Yangtzeella occurs sporadically in a few microplates or terranes, such as Tarim, Chu-Ili (southern Kazakhstan) and Taurides (southern Turkey) during the Dapingian and Darriwilian. Worldwide, Yangtzeella became extinct by the end of the Darriwilian. [ABSTRACT FROM AUTHOR]

Late Ordovician strophomenide brachiopods (superfamilies Strophomenoidea and Plectambonitoidea) from the upper Changwu Formation (mid Ashgill, late Katian) of Jianglütang, Chun’an County, western Zhejiang Province, consist of ten genera and 12 species. Five new species of three new genera are recognized: Chunanomena triporcata, Chunanomena sembellina, Cheramomena subsolana, Lateriseptomena modesta, and Lateriseptomena rugosa. The strophomenide brachiopods from the upper Katian strata described in this study and those from the border region of Zhejiang and Jiangxi provinces reported in previous work contain 16 strophomenoid and 12 plectambonitoid genera, and most of the strophomenoids are endemic to South China. Numerical analysis of well-documented late Katian strophomenide brachiopod faunas indicates a strong provincialism, characterized by the highly distinct North American province (Laurentia), the South China-Kazakhstan province, and the Avalonia-Baltica province (Wales, Belgium and Sweden). Surprisingly, the Girvan district of Scotland, which was a peri-Laurentian terrane during the Ordovician, contains a late Katian brachiopod fauna that is more closely related to the contemporaneous brachiopods of Avalonia-Baltica than to those of North America. [ABSTRACT FROM AUTHOR]

Sixteen species from the Lower Silurian (mostly Aeronian and rarely Telychian) of South China have been assigned previously to the brachiopod family Pentameridae, mainly to the genus Pentamerus. Study of intrapopulation variation suggests that 13 species from the upper Aeronian Lojoping Formation of the Yichang area, western Hubei Province, can be synonymized with Sulcipentamerus dorsoplanus, the most abundant pentamerid species of South China but confined to the Yichang area. The conspicuously high and obtuse ventral umbo, strong ventribiconvexity and a sulcate anterior commissure warrant genus status for Sulcipentamerus, independent of Pentamerus. True Pentamerus is rare in South China, known only from upper Aeronian rocks of Guizhou Province. Multivariate analyses indicate that Aeronian pentameride brachiopods of South China are characterized by a high level of provincialism, distinct from those of Laurentia. Also, the Aeronian pentamerides of South China or Laurentia have a low degree of similarity to those of Baltica, Siberia, Avalonia, Kazakhstan and other palaeotropically located plates or terranes. Besides South China and Laurentia, the pentamerides of other palaeotropical regions constituted a relatively tight cluster. This suggests that the palaeogeographical positions of South China and Laurentia only allowed limited or periodic faunal exchange of these generally large-shelled brachiopods adapted to living in relatively shallow, warm waters. [ABSTRACT FROM AUTHOR]

The Ordovician radiation was one of the most marked and sustained increases in Phanerozoic biodiversification; nevertheless it occurred against a background of minimal global climatic and environmental perturbations. Detailed investigations of the Ordovician successions on the Yangtze Platform of the South China palaeoplate indicate that: (1) the brachiopod α- and β-diversity changes are diachronous; (2) macroevolutionary patterns were different across the South China palaeoplate, with the Early Ordovician brachiopod radiation first occurring in normal marine, shallow-water environments and then moving gradually to both nearer-shore and offshore locations; (3) the main contributors to the initial Ordovician brachiopod radiation were the Orthida and Pentamerida; the typical Ordovician brachiopod fauna, dominated by the Orthida and Strophomenida, did not appear until the late Mid Ordovician ( Undulograptus austrodentatus Biozone) when the Strophomenida apparently replaced the dominant position of the Pentamerida within the fauna; (4) different ecotypes (e.g., sessile benthos, mobile benthos together with pelagic and planktonic organisms) demonstrate substantially different macroevolutionary patterns. The Ordovician brachiopod radiation of South China was apparently earlier than that suggested by global trends together with the data available from other palaeoplates or terranes, which may be related to its unique palaeogeographic position (peri-Gondwanan terrane gradually moving to equatorial latitudes). [ABSTRACT FROM AUTHOR]

Available data on the temporal and geographical distribution of Middle–early Late Ordovician trilobites in South China were reviewed under a high-resolution biostratigraphical framework to investigate the diversity dynamics and explain the faunal turnover and radiation pattern of trilobites during the Middle Ordovician. Three macroevolutionary phases are recognized on the basis of the diversity changes at taxonomic levels. Cluster analysis shows three trilobite groups, two distinct trilobite faunas and three faunal turnovers through nine time slices. Three trilobite groups (Groups A, B and C) are coupled with three macroevolutionary phases, and characterized by different proportions of the Whiterock Fauna. Two distinct trilobite faunas (Early–Middle Ordovician and Late Ordovician Trilobite Faunas) and three faunal turnovers could be recognized at different similarity coefficients, their replacements were mainly affected by changes of sea level and substrate conditions. The trilobite radiation was manifested by the development, expansion and domination of the Whiterock Fauna (part of the Paleozoic Evolutionary Fauna) through the Middle Ordovician. The first diversity acme of trilobites occurred during the Dapingian–early Darriwilian, while the radiation centre gradually shifted from inner platform to outer platform environments. From the end Darriwilian onwards, elements of the Whiterock Fauna had further developed and dominated all environmental settings from the inner platform to the lower slope, coinciding with the second and more extensive radiation of trilobites in South China. Two phases of radiation may have been directly triggered by two major transgressions during the late Dapingian–early Darriwilian and the late Darriwilian–early Sandbian respectively. In addition, climate cooling and various substrate conditions, as well as the increased oxygen levels in the atmosphere and marine water, nutrients and tectonic movements during the Middle Ordovician may have provided essential conditions for the trilobite radiation. • Three macroevolutionary phases of South China trilobites based on diversity changes. • Heatmap of trilobites based on cluster analysis shows trilobite groups and faunal turnovers. • Development, expansion and domination of the Whiterock Fauna along environmental gradients. • Status of the Whiterock Fauna in the macroevolution of the Ordovician trilobite and Paleozoic Fauna. • Trilobite radiations of South China were closely related to sea level changes. [ABSTRACT FROM AUTHOR]

During the Early-Middle Ordovician, the Yangtze Platform in South China was drowned, as indicated by the replacement of pure grey grainstones and packstones of the Hunghuayuan Formation by purple red, argillaceous limestone of the Zitai Formation and correlative units, which are mixed siliciclastic and carbonate deposits. The Xiangshuidong Section, located in Songzi City, southwestern Hubei Province, was selected to study the process in detail. Cluster analysis of point-count groups of the Hunghuayuan and the Zitai formations, indicates that the former contains six microfacies: MF-1 peloidal grainstone, MF-2 thrombolitic grainstone, MF-3 oolitic grainstone, MF-4 bioclastic grainstone, MF-5 lithoclastic grainstone, MF-6 interreef bioclastic grain-packstone, indicating a shelf setting before drowning, while the latter contains seven microfacies: MF-7 bioclastic grainstone, MF-8 bioclastic grain- to packstone, MF-9 bioclastic packstone, MF-10 bioclastic wackestone, MF-11 argillaceous bioclastic wackestone, MF-12 open-marine bioclastic wackestone, MF-13 calcimudstone, indicating the ramp setting during and after the drowning. The drowning was gradual and fluctuating, starting as a marginal shoal, through the inner ramp, and becoming a stable ramp setting. This drowning is mainly attributed to a global sea-level rise, and an increase of terrigenous supply that resulted from local tectonic movement (i.e. the initiation of collision between the South China and Cathaysia blocks). After drowning, red offshore marine facies were well developed along the platform margin, indicating an oxic sea bottom environment during the first acme of GOBE in South China. The changes in environments associated with this transition may have provided new evolutionary opportunities that contributed to the Middle Ordovician diversification. [ABSTRACT FROM AUTHOR]

The Late Ordovician was a critical interval in geologic history, during which both the biosphere and marine environments underwent severe perturbations, including one of the ‘Big Five’ Phanerozoic mass extinctions and the massive but short-term (~ 0.5-Myr) Hirnantian glaciation. The onset and termination of the Hirnantian glaciation have been widely accepted as the triggers for the two extinction pulses that comprise the Late Ordovician biocrisis, but the mechanisms that caused the Hirnantian glaciation itself remain poorly known. Here, we analyze the nitrogen isotope composition (δ 15 N) of two sections in South China (Wangjiawan and Nanbazi) in order to better understand nitrogen cycle perturbations in the Late Ordovician ocean and their relationship to contemporaneous climatic and biogeochemical changes. Low δ 15 N (~ 1‰) in the upper Katian and lower Rhuddanian of both sections suggests intensive (i.e., near-quantitative) denitrification and, thus, nitrogen fixation as the main source of biologically available nitrogen for primary producers. A positive δ 15 N excursion in both sections during the Hirnantian indicates weaker (i.e., non-quantitative) denitrification, possibly as a result of more vigorous thermohaline circulation and improved ocean ventilation. Weaker denitrification would have reduced the flux of N 2 O, an intermediate product of denitrification, to the atmosphere. N 2 O is a potent greenhouse gas, and a major decline in its production would have led to cooler climatic conditions and, ultimately, the Hirnantian glaciation. A global survey of published nitrogen isotope records suggests that similar processes operated broadly within the Late Ordovician global ocean. [ABSTRACT FROM AUTHOR]

Abstract: In the immediate aftermath of global extinctions, organisms were normally much smaller than those prior to these events. This ‘Lilliput Effect’ can be subdivided into two types: 1) a specific type, following the original definition of the effect which targets species-level taxa associated with inhospitable environments, and 2) a more general type, related to the reactions of higher-rank taxa above the species-level. The body sizes of brachiopods from South China through the Ordovician and Silurian transition (Late Katian, Hirnantian, and earliest Rhuddanian) are compared at generic, superfamilial, ordinal, and class levels. The results indicate that the body sizes of the taxa of lower rank (e.g. genus-level) are highly variable within these different intervals. The type of evidence for the Lilliput Effect through the end Ordovician mass extinction is thus quite different from that of the end Permian mass extinction probably reflecting differences in the intensity of these two major bioevents. However, the relationships between the contrasting trends in body-size change of some taxa of higher rank (e.g. at the ordinal-level) and the relative dominance of these taxa in the latest Ordovician and earliest Silurian suggest that the brachiopods of the two major Ordovician groups, the strophomenoids and orthoids, adopted different survival strategies during and immediately after the crisis from those of the pentamerides and rhynchonellides, that were common in Silurian assemblages. [Copyright &y& Elsevier]

9172 Conodonts have been recovered from the uppermost Hunghuayuan Formation and the Zitai Formation at two sections in Shitai County, southern Anhui Province, South China, which was situated close to the margin of the Lower Yangtze Platform during the Early to Middle Ordovician. Systematic and multivariate statistical studies on these conodonts permit recognition of seven conodont biofacies: Tropodus biofacies, Diaphorodus biofacies, Oepikodus biofacies, Baltoniodus biofacies, Paroistodus biofacies, Periodon biofacies and Protopanderodus biofacies. Each biofacies is restricted to a particular lithofacies and stratal position and shows a consistent order and/or position within the succession. Turnover of these conodont biofacies is related to sea-level changes. The transgressive–regressive patterns demonstrated by the conodont biofacies compare closely to published sea level curves for South China, and highlight the utility of conodont biofacies as a means of confirming sedimentological evidence of relative sea-level change. [ABSTRACT FROM AUTHOR]