Yuandong Zhang

The Central Guizhou and Yi- chang uplifts, Upper Yangtze region, between Ordovician and Silurian

The Central Guizhou and Yichang Uplifts are present in central Guizhou to western Hubei. Biostratigraphic evidences from more than 20 sections in 14 counties of this region provide the data about the duration of these uplifts. Although this duration differs from locality to locality, it is mainly from Ashgillian to Rhuddanian. The uplifts result from a horizontally driven movement to the South China Paleoplate from an uncertain block in southeast. Global sea-level drop during the end of the Ordovician made the uplifts obvious, particularly the Central Guizhou Uplift. It might have emerged above sea level in the short interval between the Ordovician and Silurian.

Conodont fauna and biostratigraphy of the Honghuayuan Formation (Early Ordovician) of Guizhou, South China

Serratognathus diversus An, Cornuodus longibasis (Lindström), Drepanodus arcuatus Pander, and eleven other less common conodonts, including Cornuodus? sp., Oistodus lanceolatus, Protopanderodus gradatus, Protoprioniodus simplicissimus, Juanognathus variabilis, Nasusgnathus dolonus, Paltodus? sp., Scolopodus houlianzhaiensis, Semiacontiodus apterus, Semiacontiodus sp. cf. S. cornuformis and Serratognathoides? sp., are described and illustrated from the Honghuayuan Formation in Guizhou, South China, concluding revision of the conodont fauna from this unit, which comprises 24 species in total. The most distinctive species in the fauna, S. diversus, consists of a trimembrate apparatus, including symmetrical Sa, asymmetrical Sb and strongly asymmetrical Sc elements. This species concept is supported by the absence of any other element types in a large collection represented by nearly 500 specimens of this species. The fauna indicates a late Tremadocian to mid-Floian age (Early Ordovician) for the Honghuayuan Formation, which was widely distributed on the Yangtze Platform in shallow water environments. Previously published biostratigraphic zonations for the Honghuayuan Formation are reviewed, and revised on the basis of our knowledge of the entire conodont fauna, supporting the establishment of three biozones, Triangulodus bifidus, Serratognathus diversus, and Prioniodus honghuayanensis biozones in ascending order. Species of Serratognathus enable correlation between Ordovician successions of South China, North China (North China Platform and Ordos Basin), Tarim Basin, and further afield into Malaysia and northwestern Australia.

On the integration of Ordovician conodont and graptolite biostratigraphy: new examples from Gansu and Inner Mongolia in China

Wang, Z.H., Bergström, S.M., Zhen, Y.Y., Chen, X. & Zhang, Y.D., 2013. On the integration of Ordovician conodont and graptolite biostratigraphy: New examples from Gansu and Inner Mongolia in China. Alcheringa 37, 510–528. ISSN 0311-5518. Few Ordovician successions in the world contain both biostratigraphically highly diagnostic conodonts and graptolites permitting an integration between standard biozones based on these fossil groups. The Sandbian Guanzhuang section in the vicinity of Pingliang in the Gansu Province has an outstanding graptolite record through most of the Nemagraptus gracilis and Climacograptus bicornis graptolite biozones. Calcareous interbeds in the succession yield biostratigraphically important conodonts, including some species used for biozonations in Baltoscandia and the North American Midcontinent. Likewise, the middle–upper Darriwilian Dashimen section in the Wuhai region of Inner Mongolia hosts both diverse graptolites of the Pterograptus elegans, Didymograptus murchisoni and lowermost Nemagraptus gracilis biozones, and conodonts of Midcontinent and Baltoscandic types. The distribution patterns of these index fossil groups provide an unusual opportunity to closely correlate conodont and graptolite biozones in the middle to upper Darriwilian to Sandbian interval. For instance, the base of the C. bicornis Biozone is approximately coeval with the base of the Baltoscandic B. gerdae Subbiozone and a level near the middle of the North American P. aculeata Biozone. Zhi-hao Wang [zhwang@nigpas.ac.cn] Xu Chen [xu1936@gmail.com], and Yuan-dong Zhang [ydzhang@nigpas.ac.cn], Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210008, China; Stig M. Bergström [stig@geology.ohio-state.edu], School of Earth Sciences, Division of Earth History, The Ohio State University, Columbus, OH 43210, USA; Yong Yi Zhen [yongyi.zhen@austmus.gov.au], Australian Museum, 6 College Street, Sydney NSW 2010, Australia.

Geobiodiversity Database: a comprehensive section-based integration of stratigraphic and paleontological data

The Geobiodiversity Database (GBDB – www.geobiodiversity.com), an integrated system for the management and analysis of stratigraphic and paleontological information, was started in 2006 and became available online in 2007. Its goal is to facilitate regional and global scientific collaborations focused on regional and global correlation, quantitative stratigraphy, systematics, biodiversity dynamics, paleogeography and paleoecology. It is unique among global, public access databases in that it is a section-based online database system, incorporating data from a wide range of disciplines of stratigraphy and paleontology, with inherent interrelationship between different kinds of data sets. It provides the capability of completely digitizing raw data, as well as integrating of different interpretations to the same paleontological and stratigraphic content. Several Windows-based visualization and analysis applications, either fully integrated with the database or supported by subset-export functions, have been developed to make the database more useful as a scientific and educational tool. The GBDB became the formal database of the International Commission on Stratigraphy (ICS) in August 2012 at the 34th International Geological Congress in Brisbane, and will produce comprehensive and authoritative web-based stratigraphic information service for global geoscientists, educators and the public.

Early Sandbian (Late Ordovician) conodonts from the Yenwashan Formation, western Zhejiang, South China

Zhen, Y.Y., Zhang, Y.D. & Percival, I.G., June, 2009. Early Sandbian (Late Ordovician) conodonts from the Yenwashan Formation, western Zhejiang, South China. Alcheringa 33, 133–161. ISSN 0311-5518. Conodonts are documented from the basal Yenwashan Formation at the Huangnitang Section (the GSSP section for the base of the Darriwilian), exposed near Changshan County town in western Zhejiang. The fauna consisting of 14 species is dominated by Pygodus anserinus, Periodon aculeatus, Protopanderodus cooperi, Costiconus ethingtoni and Dapsilodus viruensis. Both P. anserinus and P. cooperi are revised as having a septimembrate apparatus. The Pa element of P. anserinus has a morphology that varies from the primitive form with node-like denticles of the fourth row only developed on the distal part of the platform, to the advanced form with a well-developed fourth row of denticles. Association of these two morphotypes of P. anserinus, and the absence of P. serra and P. xinjiangensis in the basal Yenwashan Formation, suggests correlation of this level with the upper part of the P. anserinus Biozone (earliest Late Ordovician). This age determination agrees with the FAD of Nemagraptus gracilis immediately below in black shales intercalated with thinly bedded limestones at the very top of the underlying Hulo Formation, and provides new data for correlation with the graptolite biozone.

Early Ordovician conodonts from Zhejiang Province, southeast China and their biostratigraphic and palaeobiogeographic implications

Forty-two conodont species are documented from the Liuxia, Shijiatou and Jingshan formations in Zhejiang Province of southeast China, located palaeogeographically on the Jiangnan Slope offshore to the Yangtze Platform. From these faunas, eight successive conodont biozones of Tremadocian to middle Floian (Early Ordovician) age are recognized, including the Cordylodus lindstromi Biozone, Cordylodus angulatus Biozone, Chosonodina herfurthi Biozone, Paltodus deltifer Biozone, Paroistodus proteus Biozone, Triangulodus bifidus Biozone, Serratognathus diversus Biozone and Prioniodus elegans Biozone. Several zonal index species of the Baltoscandian succession—Paltodus deltifer, Paroistodus proteus and Prioniodus elegans—are described and illustrated in detail for the first time from South China. Co-occurrence of P. proteus and Serratognathus bilobatus in several samples below the appearance of P. elegans also confirms correlation of the S. diversus Biozone (basal Floian) with the upper P. proteus Zone of the Baltoscandian succession. These Zhejiang faunas are dominated by pandemic forms, and are similar to those of the Open-Sea Realm elsewhere, inhabiting deep, offshore environments.

New material from the Ordovician of China indicates that Inocaulis is a graptolite

Muir, L.A., Zhang, Y.-D. & Lin, J.-P. 2012. New material from the Ordovician of China indicates that Inocaulis is a graptolite. Alcheringa 37, 558–559. ISSN 0311-5518. The problematic Early Palaeozoic fossil Inocaulis has been regarded as an alga, a graptolite and a hydroid by different authors. A new specimen from the Ordovician (late Darriwilian) of Guizhou Province (China) shows fusellar banding, confirming that it is a benthic graptolite. Lucy A Muir [lucy@asoldasthehills.org], Yuan-dong Zhang [ydzhang@nigpas.ac.cn], Jih-Pai Lin [jplin@nigpas.ac.cn] (corresponding author), State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, No. 39 East Beijing Road, Nanjing 210008, PR China. Received 13.12.2012; revised 10.5.2013; accepted 13.5.2013.

Heterogenous oceanic redox conditions through the Ediacaran-Cambrian boundary limited the metazoan zonation

Recent studies have enhanced our understanding of the linkage of oxygenation and metazoan evolution in Early Cambrian time. However, little of this work has addressed the apparent lag of animal diversification and atmospheric oxygenation during this critical period of Earth history. This study utilizes the geochemical proxy and N isotope record of the Ediacaran–Cambrian boundary preserved in intra-shelf basin, slope, and slope basin deposits of the Yangtze Sea to assess the ocean redox state during the Early Cambrian metazoan radiation. Though ferruginous conditions appear to have prevailed through the water column during this time, episodes of local bottom-water anoxia extending into the photic-zone impacted the slope belt of the basin. Heterogenous oceanic redox conditions are expressed by trace element concentrations and Fe speciation, and spatial variation of N isotopes. We propose that the coupling of ocean chemistry and Early Cambrian animal diversification was not a simple cause-and-effect relationship, but rather a complex interaction. Specifically, it is likely that animal diversification expanded not only temporally but also spatially from the shallow shelf to deep-water environments in tandem with progressive oxygenation of the extensive continental margin.

Tubes or cell sheet? A 3-D reconstruction of Halysis Høeg, 1932, from the Upper Ordovician of South China

Halysis is a microfossil found in Ordovician to Devonian shallow-marine carbonates. Up to now, it is only known from thin-sections, and therefore its three-dimensional shape and its systematic position are controversial. Halysis is described as a chain-like microfossil with a shape of the single “chain links” ranging from circular to rounded rectangular. Given that Halysis commonly co-occurs with calcareous algae, it is assumed to also be an alga. Interpretations of the anatomy propose a filiform or tubiform shape. Even a unistratose sheet of cells has been discussed. Since Halysis is comparatively rare, its shape has not been resolved up to now. For the present study, 52 out of several hundred specimens from an Upper Ordovician shallow-water limestone of South China have been investigated in detail, which for the first time offers the opportunity to analyze a great number of sections through Halysis. A three-dimensional computer model of Halysis has been constructed in order to set up planes sectioning the model. These simulated sections have been compared to those from Halysis in thin-sections. The results show that Halysis represents a microfossil with a morphology consisting of parallel juxtaposed, partly branching tubes. A single sheet of cells, which was recently proposed as shape of Halysis, can clearly be excluded.

Discovery of missing link between demosponges and hexactinellids confirms palaeontological model of sponge evolution

The two major extant groups of siliceous sponges, Demospongiae and Hexactinellida, are generally regarded as sister groups forming the clade Silicea, although the nature of their last common ancestor is uncertain. The fossil record contains a diverse range of basal demosponges that appear to have evolved from hexactine-bearing reticulosan ancestors, although a compelling morphological intermediate has not previously been discovered. Here we describe a new species of fossil sponge, Conciliospongia anjiensis gen. et sp. nov., from the Late Ordovician (~444 Ma) Anji Biota of South China. This species has a reticulate, tufted skeleton of minute monaxon spicules, characteristic of the fossil demosponge family Hazeliidae and modern heteroscleromorphs, with hexactine spicules and a globose body form inherited from reticulosan ancestors. This transitional morphology had previously been hypothesized in palaeontological studies. This morphological intermediate between two extant classes further confirms siliceous sponge monophyly and demosponge–hexactinellid spicule homology, and supports the primitive, stem-silicean interpretation of simpler-structured fossil reticulosans.