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China presently comprises several tectonic blocks and regions assembled over geological time and having independent histories. During the Ordovician, these blocks included South China, North China, Tarim, Qaidam, Junggar, Qiangtang-Qamdo, Lhasa and partially Himalaya, Sibumasu and Indochina, as well as the Altay-Xingâan and Songpan-Garze fold belts, which were discrete but adjacent. Twelve stratigraphic megaregions bounded by tectonic sutures or major fault zones are recognised for the Ordovician System. Some of them are further subdivided into regions according to specific lithological and biotic facies or distinct stratigraphic successions. The palaeontological features and biostratigraphic framework of these stratigraphic megaregions and regions are summarised. The unified biostratigraphic framework presented herein includes 33 graptolite and 27 conodont biozones through the Ordovician, together with supplementary biozones, communities or associations of brachiopods, trilobites, cephalopods, chitinozoans, acritarchs and radiolarians. With the constraints of integrative chronostratigraphy, biostratigraphy, chemostratigraphy, cyclostratigraphy and magnetostratigraphy, along with some geochronological data, our understanding of the temporal and spatial distribution of the Ordovician lithostratigraphic units on these major blocks has been significantly advanced. The refined integrative stratigraphic framework of the Ordovician provides a precise constraint on the major tectonic orogenies and biotic events evident in China.

Variation in the relative abundance of the stable carbon isotopes has been widely used to correlate Ordovician marine successions over the past two decades. To date, only a few of studies of Ordovician carbon chemostratigraphy have been conducted in South China. Most of the previous studies in this field have focused on specific time intervals and/or events in the Middle and Upper Ordovician. The Lower and Middle Ordovician of the Yangtze Platform is typically represented by a sedimentary succession dominated by carbonate rocks, which is ideal for studying the carbon chemostratigraphy. Three sections spanning the Nantsinkuan/Lunshan, Fenhsiang, Hunghuayuan, and Dawan/Zitai formations, corresponding to the TremadocianâDapingian in age, have been sampled for high-resolution δ13C chemostratigraphy. Our new δ13C data reveal five tie-points with the potential for global correlation: (1) a positive δ13C excursion in the lower Nantsinkuan Formation within the Tremadocian Rossodus manitouensis Zone; (2) an excursion with two peaks roughly within the late Tremadocian Paltodus âdeltiferâ Zone; (3) a positive δ13C shift in the lower Hunghuayuan Formation, within the early Floian Serratognathus diversus Zone; (4) a gradual positive δ13C shift in the late Floian, ranging from the uppermost S. diversus Zone to the basal Oepikodus evae Zone; (5) a minor negative shift in the lower Dawan/Zitai Formation, within the early Dapingian Baltoniodus triangularis Zone. These excursions are herein used for correlation of the Yangtze Platform strata with successions from South China, North China, the Argentine Precordillera, North America and Baltica. From a palaeogeographical perspective, the Gudongkou, Xiangshuidong and Daling sections represent depositional environments along an inner to outer ramp profile. The δ13C data from these sections show successively heavier (higher) δ13C values with increasing depositional depth, which can be interpreted as due to remineralization of organic carbon within the carbonate rocks formed in the shallow-water environment.

A new halysitid species, Halysites gaojiangensis, is systematically described from the middle Rhuddanian (Llandovery, Silurian) Wulipo Bed at Gaojiang, Meitan County, northern Guizhou Province, Southwest China. It provides new data for further investigation of the tabulate faunal change across the Ordovician–Silurian transition. Halysites across the Ordovician–Silurian transition is reviewed and briefly discussed.

Species-abundance models have been an important method for investigating community structure in modern biology in the past decades. Different species-abundance models can reflect different ecological meanings. The method is relatively new to palaeoecology. We take the latest Ordovician–earliest Silurian Cathaysiorthis brachiopod fauna of South China as an example, program the calculation in the R language, introduce the application of the species-abundance models and discuss the relationship between the abundance model and the ecological bathymetry of a certain brachiopod fauna. Finally, we testify the validity of the method and suggest that the species-abundance models should be treated as one of the supporting evidences in investigating the brachiopod palaeoecology.

The Saucrorthis Fauna is a brachiopod-dominated shelly fauna developed in relatively deeper-water benthic regimes of a few peri-Gondwana terranes (e.g. northern Iran) and palaeoplates (South China and Sibumasu) during the Darriwilian (late Middle Ordovician). It has its longest geological range, widest palaeogeographic distribution, most abundant and diversified brachiopod taxonomic composition and most complex palaeoecological differentiation in South China, where it concentrated in the centre of the Upper Yangtze Platform. The generally low similarity coefficients (

The eastern equatorial Pacific cold tongue (EEP-CT) today asserts a vital influence on ocean-atmosphere CO2 exchange and global climate patterns. Here, we report a similar equatorial cold tongue in the Late Ordovician peri-Gondwana region during drastic greenhouseicehouse climate swings and the first mass extinction. Paleontological, sedimentological, and new stable-oxygen-isotope data from conodont apatite point to a change from warm-water to cool-water tropical depositional environments in the South China plate from Early to Late Ordovician. This apparently contradicts the current paleogeographic reconstructions of a coeval northward drift of South China from subtropical peri-Gondwana to the equator. The trend of climate cooling coincided with the origin and diversification of the Foliomena fauna in South China during the Late Ordovician, and the absence of reef-building sponges and corals. This was in sharp contrast with the Calathium calcareous sponge reefs in Early Ordovician warm-water settings. In this study, we compare the paleogeographic setting of the South China plate in the Late Ordovician with the EEP-CT today where cool-water depositional environments prevail because of cold upwelling and westerly currents. [ABSTRACT FROM AUTHOR]

A complete coral succession through the Ordovician-Silurian transition in South China reveals an adaptive phase during the Hirnantian glaciation, followed by an early survival phase and finally a late survival phase that persisted into the early Silurian. We demonstrate that a coral assemblage of latest Hirnantian to earliest Silurian age, remarkably similar to those from the Edgewood fauna known from Laurentia, occurs stratigraphically above the typical Hirnantian fauna. This, in combination with other evidence (e.g. brachiopods, lithology and chemostratigraphy), suggests the Edgewood fauna probably post-dated the early-middle Hirnantian glaciation, rather than being coeval with the older glacial-related Hirnantia fauna. Evidence from South China shows that the Edgewood fauna appeared in the very latest Hirnantian and extended into the middle Rhuddanian, considerably younger than previously believed. Such a new correlation necessitates a reassessment of the influence of the end-Ordovician glaciation on biotas. We argue that this major glaciation probably would have substantially affected the ecosystem even in tropical regions, as shown by the development there of the Hirnantia fauna or, alternatively, the presence of a conspicuous stratigraphic hiatus. This suggests a surprisingly rapid biotic recovery during the subsequent postglacial transgression, represented by the flourishing of comparatively diverse shelly faunas (e.g. the Edgewood fauna and the Cathaysiorthis brachiopod fauna) in nearshore shallow water environments from Laurentia to eastern peri-Gondwana terranes or blocks (e.g. South China). [ABSTRACT FROM AUTHOR]

A relatively diverseSaucrorthisbrachiopod fauna is reported for the first time from the Sibumasu palaeoplate in the Shihtien Formation (Darriwilian, upper Middle Ordovician) at Laojianshan of Baoshan, western Yunnan Province, southwest China. It contains 25 brachiopod genera, amongst which orthides, strophomenides and billingsellides are predominant, but quantitativelySaucrorthisandLeptestiinaare the most abundant. Numerical analyses of 23 global Darriwilian brachiopod faunas show two major clusters, theSaucrorthisGroup and theAporthophylaGroup, representating two major palaeobiogeographical regions developed during the Darriwilian, corresponding to lower and higher palaeolatitudinal habitats, respectively. [ABSTRACT FROM AUTHOR]

The article presents various commentaries on Case 3632 by Drs. Modzalevskaya and Alvarez which appeared on pages 185-189 of the issue, supporting their proposal for the conservation of the specific name Anathyris monstrum. A list of reasons to justify each of the author's agreement to the proposal is also discussed.

The upper Daguanshan Formation (middle Expansograptus hirundo graptolite biozone, Dapingian, early Middle Ordovician) of the Shuanghe area, Changning County, southern Sichuan Province, contains three new genera and species of strophomenoids: Ochyromena plana, Shuangheella elongata, and Primotimena globula, which are attributed to the Strophomenidae, Rafinesquinidae and Glyptomenidae respectively. These are the earliest known strophomenoids from the South China palaeoplate, and also the oldest rafinesquinid and glyptomenid brachiopods worldwide. Global review of the superfamily Strophomenoidea of Middle Ordovician age suggests that the first diversity peak at the species level occurred in late Darriwilian (Llanvirn) time, mainly as a result of the rapid diversification of the family Strophomenidae. The first appearance datum (FAD) of strophomenoids and their possible westward dispersal were from North China (latest Floian) and/or South China (early Dapingian), through the Chu-Ili terrane of Kazakhstan, Iran, and Baltica (early Darriwilian), to Avalonia and Laurentia (late Darriwilian). This points to the existence of early diversification hotspots of the strophomenoid superfamily in the North and South China palaeoplates during the early Middle Ordovician in generally shallow water (corresponding to BA2) environments. The high degree of similarity in the external morphology and ventral interior of the three new genera indicates that the early diversification of strophomenoids began with differentiation of the cardinalia, especially in the configuration of the bilobed cardinal process, a key evolutionary novelty for the strophomenoids. [ABSTRACT FROM AUTHOR]

A collection of numerous crinoid pluricolumnals from the uppermost Darriwilian (Middle Ordovician) of Tibet were derived from one biological species of crinoid. The specimens were collected from well-lithified, bioclastic shelf limestones of the upper part of the Lower Chiatsun Group, Pygodus serra Biozone; coeval rocks of similar lithology outcrop at the summit of Everest. A new crinoid morphospecies, Segmentocolumnus (col.) hanshessi, is tentatively considered a 'stem-group cladid', perhaps a dendrocrinid. The proxistele is broad and pentagonal in section with a broad, pentagonal axial canal; the mesistele of similar gross morphology is more slender with a regularly heteromorphic column and a similarly wide axial canal; the dististele is a terminal dendritic radice with a pentastellate axial canal. In the mesistele, the meric sutures correspond to the centres of the sides of the column, but in the dististele they occur in the angles. This range of morphologies would have led to their inclusion in at least two morphogenera if they had not been closely associated; as they belong to a single biological species, they have been 'lumped' together herein. This is a rare contribution to our knowledge of the early crinoids from a region outside Europe and North America. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A continuous Ordovician-Silurian boundary section from the upper Wufeng Formation through the Kuanyinchiao Formation to the lower Lungmachi Formation has been carefully measured and collected at Shuanghe of Changning, southern Sichuan Province. For the first time, the temporal changes of α- and β-diversities of the Hirnantia fauna have been discussed in great detail. The general trend of brachiopod diversity change, increasing upward, is consistent with the regional trend of the Yangtze Platform, which had been controlled by both intrinsic and extrinsic factors. However, the sudden drop of diversity for a short period in the upper Kuanyinchiao Formation might have been controlled by environmental factors rather than normal faunal turnover. Synecological analysis using numerical methods recognizes two brachiopod-dominated associations of the Hirnantia fauna, the Dalmanella-Kinnella Association and the Mirorthis Association, both living in an offshore, deeper water environment corresponding to BA3-upper BA4, particularly lower BA3. [ABSTRACT FROM AUTHOR]

Epipunctae, a new type of shell perforation, are well developed in typical taxa of the family Plaesiomyidae, a group of common orthide brachiopods from Laurentia and some other tropically located tectonic plates of Late Ordovician age. These minute, prominently elongate, tubular structures are similar to endopunctae in size and density, but differ in being oblique, intersecting the shell surface at a relatively low angle, and being confined largely to the outer portion of the shell wall. The tubules are similar in orientation to aditicules within the same shells but are much smaller and denser, usually aligned along fine growth lines and arranged in crude longitudinal columns. Exceptionally preserved phosphatic molds of bundled setal canals inside epipunctae and aditicules, described for the first time in this paper, are direct evidence that these two types of tubular structures of different sizes had the same function of housing sensory setae along the shell margin, but both the setae and the tubules became abandoned in the outer portion of the shell wall through burial by the secondary shell layer when the shell margin migrated forward. Epipunctae have been found so far only in plaesiomyid shells, but aditicules are common in many groups of the order Orthida. The taxonomic value of epipunctae is shown by a reassessment of Pionorthis Schuchert and Cooper, 1932. The hypotype previously regarded widely, but erroneously, as the archetype of `Orthis sola' Billings, 1866, the type species of Pionorthis, is allied to Plaesioinys Hall and Clarke, 1892. It bears the characteristic epipunctae. The holotype of Orthis solo is a dalmanelloid shell with true punctae, assignable to Mendacella Cooper, 1930. This warrants rejection of the genus Pionorthis. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Studies the evolution of the Gnamptorhynchos, a rhynchonellid-like orthid brachiopod from Platystrophia in North America. Shell size and morphology; Dental plates; Morphological adaptations; Characterization of Gnamptorhynchus manitobensis species.

The article reports on the meganodular limestone in South China. It highlights time-specific facies-based three-dimensional network structure of the Upper Ordovician Pagoda Formation in the country. It also outlines the basis of the analysis on the formation which involves the use of geochemical, paleontological and sedimentological information.