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The conodont fauna from the Willara Formation, a carbonate-dominated stratigraphic unit widely distributed in the subsurface Canning Basin of Western Australia, is represented by 41 species, including a new species, Erraticodon neopatu Zhen n. sp. The Jumudontus gananda and Histiodella altifrons biozones are recognized in the lower and upper parts, respectively, of the Willara Formation. Deposited primarily in shallow nearshore settings, the Willara Formation is characterized by the occurrence of predominantly long-range coniform species of Triangulodus, Scalpellodus, Drepanoistodus, Drepanodus, and Kirkupodus. Several widely distributed age-diagnostic species, including Histiodella altifrons, Histiodella holodentata, Histiodella serrata, and Jumudontus gananda, serve as keys for biostratigraphic analysis and correlation. Our study also shows that the basal and top boundaries of the Willara Formation are diachronous across the basin, extending from the middle Floian (Oepikodus communis Biozone) to middle Darriwilian (Histiodella holodentata-Eoplacognathus pseudoplanus Biozone). This contribution provides crucial new biostratigraphic data for precise correlation of the Willara Formation with its time equivalents regionally and internationally.

Ordovician conodonts representing 28 genera and 28 named and three unnamed species were identified from 740 chert and siliceous siltstone spot samples (>3 000 thin sections) from deep-water turbiditic sequences of the Lachlan Orogen in central and southern New South Wales, Australia. Based on these faunas, a new conodont biozonal scheme has been established to divide the Ordovician turbiditic successions of the Lachlan Orogen into 12 superbiozones and biozones. They are (in ascending order) the Paracordylodus gracilis Superbiozone (including the Prioniodus oepiki Biozone), Periodon flabellum Superbiozone (including the Oepikodus evae Biozone in the lower part), Periodon hankensis Biozone, Periodon aculeatus Superbiozone (including the Histiodella labiosa, Histiodella holodentata, Histiodella kristinae, Pygodus serra and Pygodus anserinus biozones) and the Periodon grandis Biozone. The Pygodus anserinus Biozone is divided further into the lower and upper subbiozones. This new conodont biozonation scheme spanning the upper Tremadocian to middle Katian interval permits precise age-dating and correlation of deep-water siliciclastic rocks that characterize the Ordovician Deep-Sea Realm regionally and internationally.

Seven conodont biozones are recognized in the carbonate-dominated shelf-marine Middle Ordovician developed in the intracratonic sedimentary basins (Canning, Amadeus and Georgina) of central and north-western Australia, in the Lachlan and New England orogens of New South Wales, and in the Takaka Terrane of New Zealand. A separate scheme identifying seven conodont biozones spanning the Middle Ordovician has also been developed for siliciclastic sequences deposited in slope-basinal environments in the Lachlan Orogen in New South Wales and Victoria. This biozonal classification consisting of two parallel biostratigraphic schemes for the shelf-marine and deep-marine successions respectively has significantly increased precision in regional and global biostratigraphic correlation and laid a solid foundation for the Middle Ordovician chronostratigraphy of Australia and New Zealand. Recognition of short-ranging pandemic species as the eponymous species of the biozones also supports direct correlation with the classical conodont successions established in Baltoscandia and the North American Midcontinent, and with those of the major Chinese terranes (South and North China and Tarim). The Lachlan Orogen appears to be globally unique in enabling correlation of contemporaneous conodont faunas over a considerable spectrum of water depths and biofacies ranging from carbonate shelves, slopes to deep-water basins.

Darriwilian to early Katian conodonts are documented herein from the Kuniutan, Datianba and Pagoda formations at the Daling section of southern Anhui Province, East China, representing a typical Or...

The Ordovician stratigraphy of southern-central Xizang (Tibet) has been revised based on new conodont data recovered from 43 samples in four stratigraphic units and their integration with existing nautiloid and graptolite data. The Histiodella holodentata and Pygodus serra biozones have been identified respectively in the Alai and Jiaqu formations of the Chiatsun Group exposed near Alai village in Nyalam County within the Himalayan terrane, and the Yangtzeplacognathus foliaceus Subbiozone (lower part of the Pygodus serra Biozone) in the Sangqu Formation exposed at the Guyu section within Zayu County in the Lhasa terrane. Recognition of these biozones has increased the precision of correlation of the middle-upper Darriwilian strata in the region. Regional reassessment of the Ordovician stratigraphy permitted by new biostratigraphic data has allowed revised definitions for the Chiatsun and Keerduo groups and the Sangqu and Xainza formations. The Chiatsun Group is defined herein to include three lithologically distinctive formations in descending order, the Jiaqu, the Alai and the Adang formations. The stratigraphic age for the Jiaqu and Alai formations in the type area ranges from the middle Darriwilian (Histiodella holodentata Biozone) to middle Katian (Hamarodus brevirameus Biozone), but the age of the Adang Formation remains less certain.

Corals representing the sole occurrence of C/S Fauna IV of the regional biostratigraphic scheme occur in limestone in the uppermost Malachis Hill Formation of the Bowan Park area, central New South...

The conodonts documented by Watson form one of the best-known middle Darriwilian faunas from Australia. The present contribution is based on the re-examination of this material. Thirty-one conodont...

Zhen, Y.Y., Normore, L.S., Dent, L.M. & Percival, I.G., 11 July 2019. Middle Ordovician (Darriwilian) conodonts from the Goldwyer Formation of the Canning Basin, Western Australia. Alcheringa 44, 2...

Zhen, Y.Y. 9 July 2019. Revision of two phragmodontid species (Conodonta) from the Darriwilian (Ordovician) of the Canning Basin in Western Australia and phylogeny of the Cyrtoniodontidae. Alcherin...

A revised conodont biozonal scheme for the Ordovician of South China is presented herein based on extensive studies following the pioneer work by the late Professor An and his co-workers in the 1980s. This new classification of 33 biozones and subbiozones includes the conodont succession of the Yangtze Platform (29 biozones and subbiozones), the Jiangnan Slope (17 biozones), and a unique succession in the Qinling Orogen (four Katian biozones). The proposed biozone scheme provides more accurate correlations of the Ordovician strata in South China. As the best known and most detailed Ordovician conodont biozone succession in eastern Gondwana and peri-Gondwana, it will serve as a standard reference for correlation not only in this region but also for comparisons with the well-established biozone successions in Baltoscandia and North America. Furthermore, this new scheme has the potential to improve the precision in reconstruction of the conodont biofacies architecture in space and time. It will also assist in advancing our understanding of the timing and magnitude of biodiversification, oceanographic, and geological events at both the local and global scale.

Conodonts and microbrachiopods of latest Cambrian–earliest Ordovician age are documented from the Handler Formation of northern Victoria Land, Antarctica. Five spot samples from allochthonous limestone clasts collected during expeditions conducted by the Korean Polar Research Institute in 2013–2014 yielded the conodonts Cordylodus proavus, C. lindstromi, Hirsutodontus simplex, and Teridontus nakamurai, associated with four species of brachiopods (two indeterminate acrotretides, a zhanatellid lingulide, and a siphonotretide tentatively referred to Schizambon reticulatus). The four conodont species are distinctive taxa occurring in the widely distributed Cordylodus lindstromi Biozone of the latest Cambrian and the Iapetognathus Biozone at the base of the Ordovician. The allochthonous limestone clasts in the Handler Formation were likely derived from now-lost carbonate shelves developed locally (in the Bowers Arc) or transported from further north. Fossil evidence from the Handler Formation indicates that the final episode of the Ross Orogeny that uplifted and deformed the Robertson Bay Group was no older than early Tremadocian (earliest Ordovician). Striking similarities in fossil content, ages and depositional settings between the limestone olistoliths in the Handler Formation and latest Cambrian–earliest Ordovician autochthonous and allochthonous carbonates of the post-Delamerian Orogen recognized in the Koonenberry Belt (Gnalta Shelf) in far western New South Wales support the depositional model considering the Robertson Bay Group as the synorogenic deposits of the Ross Orogeny.

The Ordovician Chiatsun Group, exposed at the Jiacun section, Nyalam, in southern Xizang (Tibet), China, is biostratigraphically one of the best constrained Ordovician sections in the Himalaya margin, and thus plays a key role in correlating the Ordovician strata of this region. The Chiatsun Group is subdivided into the Adang Formation, the Alai Formation, and the Jiaqu Formation, in stratigraphically ascending order. Based on limestone samples collected from the Alai and Jiaqu formations, the Darriwilian chemostratigraphy is established and confirmed by conodont biozonation data. The Middle Darriwilian δ13C excursion (MDICE) is recorded in the Himalaya margin for the first time, with an amplitude of about 2‰. Its rising limb starts near the boundary of the Histiodella holodentata and Histiodella kristinae zones, and the excursion reaches its maximum values in the Pygodus serra Zone. The decreasing limb is not exposed. The carbon isotope curve with its pronounced onset of the MDICE documents a high potential for chemostratigraphic correlations helping to disentangle the Kurgiakh orogeny in the Himalaya margin. The MDICE recorded in southern Xizang correlates well with that in Baltoscandia, Laurentia, the Argentine Precordillera, Siberia, South China, North China, and Tarim, and extends the distribution of the MDICE to a new block, and thereby strengthens its global significance.

New stable carbon isotope data (δ13Ccarb and δ18Ocarb) from the Lower–Middle Ordovician is presented from petroleum exploration well Olympic 1 in the Canning Basin, Western Australia. Olympic 1 continuously cored 319.53 m of sedimentary strata, from the basal part of the Willara Formation through the majority of the Nambeet Formation. This cored section comprises carbonate and siliciclastic deposits that constitute the primary fill sequence of the Canning Basin. Previous studies report CA-IDTIMS dates between 479.37 ± 0.16 Ma and 470.18 ± 0.13 Ma from bentonite beds within the Nambeet Formation and lower Willara Formation in Olympic 1. Four conodont biozones ranging from the Paroistodus proteus conodont Biozone (upper Tremadocian) to the Jumudontus gananda Biozone (upper Floian to lower Dapingian) have been identified from the same interval. The new carbon isotope data from the Olympic 1 core are superimposed on this robust framework to provide context for Tremadocian to Dapingian stable isotope trends for Australia. Three positive δ13Ccarb excursions are identified in the Olympic 1 δ13Ccarb isotope curve, which are correlated to the global generalized δ13C curve. The highest of these occurs in the basal Willara Formation, immediately above a CA-IDTIMS radioisotopic date of 470.18 ± 0.13 Ma within the upper Floian to lower Dapingian J. gananda conodont Biozone. The second falls in the upper Nambeet Formation, immediately above a middle Floian CA-IDTIMS radioisotopic date of 472.82 ± 0.13 Ma, and within the Oepikodus communis conodont Biozone. The oldest positive excursion occurs in the lower Nambeet Formation, immediately above a CA-IDTIMS radioisotopic date of 479.37 ± 0.16 Ma, and within the upper Tremadocian P. proteus conodont Biozone. Correlation of the Olympic 1 δ13Ccarb curve to Lower-Middle Ordovician δ13Ccarb curves from the Great Basin USA, Argentine Precordillera, Western Newfoundland and South China confirms the global distribution of dissolved inorganic carbon preserved in the geological record. This integrated record may be a useful reference for constraining the timing of major oceanographic events, and a key to establishing better links between the sedimentary successions of Western Australia and the larger Ordovician world.

Zhen, Y.Y. & Percival, I.G. March 2017. Late Ordovician conodont biozonation of Australia—current status and regional biostratigraphic correlations. Alcheringa 41, xxx–xxx. ISSN 0311-5518.Seven conodont biozones are recognized in the Upper Ordovician of Australia. The Pygodus anserinus, Belodina compressa and Phragmodus undatus–Tasmanognathus careyi biozones are successively represented in the Sandbian. Although the Erismodus quadridactylus Biozone of the late Sandbian North America Midcontinent succession was previously recognized in the Stokes Siltstone of the Amadeus Basin and the Mithaka Formation of the Georgina Basin in central-north Australia, we argue for a middle–late Darriwilian age for these two units. Four conodont biozones, from oldest to youngest the Taoqupognathus philipi, T. blandus, T. tumidus–Protopanderodus insculptus and Aphelognathus grandis biozones, are established in the Katian of eastern Australia. Taoqupognathus species are particularly useful in correlation of the lower–middle K...

Funded by Geoscience Australia’s Exploring for the Future initiative and operated by the Geological Survey of Western Australia, the Waukarlycarly 1 deep stratigraphic drillhole was designed to investigate the geology of the little-known Waukarlycarly Embayment and assess the petroleum, mineral, groundwater and CO2 storage potential of the area. Based on consultation with the Western Desert Lands Aboriginal Corporation on the cultural significance of the name, Waukarlycarly, it has been agreed to change the name of the well to Barnicarndy 1 and the tectonic subdivision to the Barnicarndy Graben. This and all future publications will now refer to the Barnicarndy 1 stratigraphic drillhole (previously Waukarlycarly 1) and the Barnicarndy Graben (previously Waukarlycarly Embayment). Drilling commenced on 1 September 2019 and reached a total depth (TD) of 2680.53m on 30 November 2019, recovering more than 2km of continuous core. The cored interval extended from 580m to TD in Neoproterozoic Yeneena Basin dolostone, which was unconformably overlain by a thick, lower Canning Basin Ordovician stratigraphy, including richly fossiliferous marine mudstones with common volcanic ash beds. A major unconformity is located at the top of the Ordovician section where it is overlain by sandstones and muddy diamictites of the Carboniferous–Permian Grant Group, followed by a Cenozoic succession near surface. Ditch cuttings were collected from surface to 580m at 3m intervals. The pre-Grant Group Paleozoic succession is unique within the Canning Basin, indicating that the Barnicarndy Graben’s depositional history is markedly different when compared with adjacent structural subdivisions, such as the Munro Arch and Kidson Sub-basin. Detrital zircon geochronology, biostratigraphy and borehole imaging interpretation assisted in the definition of two new geological units within the Ordovician stratigraphy of Barnicarndy 1: the Yapukarninjarra and Barnicarndy formations. Preliminary routine core analysis data indicates the potential for CO2 storage within the Barnicarndy Formation beneath a Grant Group seal. The well also provides new insights into the structural interpretation of the Barnicarndy Graben.

Zhen, Y.Y., Wang, G.X. & Percival, I.G., August 2016. Conodonts and tabulate corals from the Upper Ordovician Angullong Formation of central New South Wales, Australia. Alcheringa 41, xxx–xxx. ISSN 0311-5518.The Angullong Formation is the youngest Ordovician unit exposed in the Cliefden Caves area of central New South Wales. Its maximum age is constrained by a Styracograptus uncinatus graptolite Biozone fauna at the very top of the underlying Malongulli Formation, but the few fossils previously reported from higher in the Angullong Formation are either long-ranging or poorly known. From allochthonous limestone clasts in the middle part of the formation, we document a conodont fauna comprising Aphelognathus grandis, A. solidum, Aphelognathus sp., Aphelognathus? sp., Belodina confluens, Drepanoistodus suberectus, Panderodus gracilis, Panderodus sp., Phragmodus undatus, Pseudobelodina inclinata and Pseudobelodina? sp. aff. P. obtusa, which supports correlation with the Aphelognathus grandis Biozone (late Kat...

Ordovician conodont studies have revealed a depositional hiatus extending from the late Floian to early Darriwilian on the North China Platform. Recognition of this widespread gap entails revision of the original concept of the Huaiyuan Epeirogeny, with definition of two distinct regional tectonic events: Event 1, which initiated this hiatus, and a subsequent Event 2 that was responsible for terminating Early Palaeozoic sedimentation in the region from the late Katian. The timing of these two events partly coincides with widely recognized eustatic sea-level falls, and separates Ordovician sedimentation into two episodes that can be broadly correlated with eustatic sea-level rises. In combination with these sea-level changes, the Huaiyuan Epeirogeny played a decisive role in shaping and controlling Ordovician sedimentation and sequence stratigraphic architecture on the North China Platform. Lower Ordovician carbonates were deposited during an apparent regression (decreasing accommodation space), resulting from rapid sediment accumulation exceeding the overall rate of basement subsidence and eustatic sea-level rise. Sedimentation ceased in the middle to late Floian when basement uplift commenced in the south and extended northward to affect the entire platform. The diachronous top surface of the Lower Ordovician succession reflects extensive erosion that is most pronounced in the south and southwest parts of the platform where the disconformity surface cut down into Tremadocian (or even upper Cambrian) strata. Deposition of the younger sequence (Darriwilian to Katian) was the result of the interplay between rejuvenated basement subsidence and the late Middle Ordovician eustatic sea-level rise. Event 2, which was initially coupled with eustatic sea-level fall induced by the end-Ordovician glaciations, terminated Ordovician deposition in the region with the top of the Ordovician marked by an unconformity, representing a hiatus of some 122 Ma extending from latest Ordovician to latest Mississippian.

The Australasian Superprovince, a biogeographical entity defined by shallow water conodont faunas that mainly inhabited Ordovician tropical zones of eastern Gondwana and peri-Gondwanan continental blocks and terranes, is characterized by the occurrence of serratognathids in the Floian. Biostratigraphic correlation of the Floian Stage within the Australasian Superprovince is based primarily on species of Serratognathus, Prioniodus and Oepikodus, which are distributed across South China, North China, the Tarim Basin, Korea, Indochina, Sibumasu, Kazakhstan and Australia. Conodont biozones from the shallow water Yangtze Platform succession of South China, from oldest to youngest the Serratognathus diversus, Prioniodus honghuayuanensis, Oepikodus communis, and O. evae biozones, correlate respectively with the Serratognathus bilobatus, Prioniodus elegans, and O. evae biozones recognized in the succession of the deeper-water Jiangnan Slope. Paroistodus proteus, a zonal index species of late Tremadocian to earliest Floian age in Baltoscandia, occurs abundantly in the slope setting of South China and in outer-shelf settings in Western Australia. Other zonal index species of the Baltoscandian middle and late Floian succession that are recognized in South China include P. elegans (only reported from the Jiangnan Slope) and O. evae, which is widespread on the slope and deeper parts of the Yangtze Platform. O. evae is, however, confined to deep water basin successions in Australia. O. communis (zonal index species for the middle Floian of the Ibexian Series in the North American Midcontinent fauna) is common in the middle-upper Floian Stage in Australia, but is relatively rare in South China.

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 Balt...

Wang, Z.H., Bergstrom, 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 lower...

Serratognathus diversus An, Cornuodus longibasis (Lindstrom), 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 F...

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,...

Zhen, Yong Yi, Nicoll, Robert S. (2009): Biogeographic and Biostratigraphic Implications of the Serratognathus bilobatus Fauna (Conodonta) from the Emanuel Formation (Early Ordovician) of the Canning Basin, Western Australia. Records of the Australian Museum 61 (1): 1-30, DOI: 10.3853/j.0067-1975.61.2009.1520, URL: http://dx.doi.org/10.3853/j.0067-1975.61.2009.1520

Erraticodon hexianensis, a conodont with an octomembrate species apparatus, is described and illustrated from the upper part of the Meitan Formation in Guizhou, South China. Cooccurrence of Erraticodon hexianensis and Lenodus variabilis at the top of the Meitan Formation in the Honghuayuan Section of Tongzi suggests an early Darriwilian age for this level. Recovery of Oepikodus communis from the base of the Meitan Formation in the Ganxi Section of Yanhe indicates a correlation with the communis Zone of the Early Ordovician.

The two oldest species of rhipidognathid conodonts, Rhipidognathus yichangensis and Bergstroemognathus extensus , are described and illustrated from the Early Ordovician Honghuayuan Formation of Guizhou, South China. Both species are interpreted to consist of a septimembrate apparatus. The form species Bergstroemognathus hubeiensis is regarded as a junior synonym of B. extensus . As currently defined, the multi-element species B. hubeiensis includes elements belonging to both B. extensus and R. yichangensis , and hence can no longer be regarded as a valid species.

Two new conodont species, Triangulodus, T. bifidus sp. nov. and T. zhiyii sp. nov., are described and illustrated from the Early Ordovician Honghuayuan Formation of Guizhou, South China. Both consist of a septimembrate apparatus having similar M and Sd elements. Triangulodus bifidus is distinguished from all other known species of Triangulodus in displaying bifurcating costae on all seven constituent elements. Although the ranges of both species overlap and extend through most of the unit, T. bifidus is more abundant in the lower part of the Honghuayuan Formation, whereas T. zhiyii is most common in the middle and upper part of the formation in the more comprehensively sampled type section. Both new species are widely distributed in South China, with T. bifidus also reported in the Lower Ordovician of the Tarim Basin.

The septimembrate conodonts Acodus triangularis (Ding in Wang, 1993) and Prioniodus honghuayuanensis n.sp., are described and illustrated from Guizhou, South China where both species are widely distributed in Lower Ordovician strata. The adenticulate A. triangularis, which ranges through the middle and upper parts of the Honghuayuan Formation, is morphologically more primitive than the denticulate P. honghuayuanensis, which is present from the uppermost Honghuayuan Formation into the lower part of the succeeding Dawan Formation. Prioniodus honghuayuanensis, elements of which were previously ascribed to Oepikodus communis (Ethington & Clark, 1964), appears to be closely related to a species of Prioniodus from the basal Whiterockian of Utah, North America. ZHEN, YONG YI, JIANBO LIU & IAN G. PERCIVAL, 2005. Revision of two prioniodontid species (Conodonta) from the Early Ordovician Honghuayuan Formation of Guizhou, South China. Records of the Australian Museum 57(2): 303–320. Records of the Australian Museum (2005) Vol. 57: 303–320. ISSN 0067-1975 www.amonline.net.au/pdf/publications/1448_complete.pdf Conodonts from the Honghuayuan Formation of Guizhou Province, South China were first studied by An (1987) in the Honghuayuan and Ganxi sections (Fig. 1). In the Honghuayuan section, An (1987) recognized three conodont assemblages with the lowermost consisting only of coniform species. The middle assemblage is characterized by the occurrence of Serratognathus diversus An, 1981. The upper assemblage is much higher in diversity, with the appearance of a number of pectiniform species of Prioniodus, Bergstroemognathus and Rhipidognathus. Similar faunas were also recorded from the Honghuayuan Formation of Yanhe, northern Guizhou (An, 1987; X.Y. Chen et al., 1995), and are widely distributed in the Honghuayuan Formation and age equivalent units in South China (An et al., 1985; An, 1987; Wang, 1993). More recently, conodont samples were collected from Lower Ordovician sections in Guizhou and other parts of South China with the aim of revising the faunas to provide support for a more precise biostratigraphic correlation and age alignment, both regionally and internationally. This revision will assist our understanding of the origin, radiation and phylogeny of the prioniodontid and related clades

Twenty species of late Middle Ordovician conodonts including two new forms, Erraticodon bellevuensis sp. nov. and Ansella? haustra sp. nov., are described and illustrated from allochthonous limestone blocks in the Oakdale Formation of the Bell River Valley, N.S.W. The co-occurrence of Paroistodus horridus, Histiodella kristinae and Appalachignathus delicalulus in the fauna suggests the limestone was originally deposited in late Darriwilian (most likely early-mid Da3) time, providing a maximum age constraint on its inclusion in the Oakdale Formation. Some faunal similarities are apparent between this conodont fauna and that from (1) allochthonous limestone clasts within the Fairbridge Volcanics below the Wahringa Limestone Member and (2) contemporaneous deep-water cherts in basinal turbidite facies of the Adaminaby Group. The latter similarity suggests that prior to downslope displacement into the Oakdale Formation, the original depositional environment of the limestone was on an unstable outer shelf edge ...

Review of the traditional separation of global Ordovician conodont distribution into the North American Midcontinent Province (NAMP) and North Atlantic Province (NAP) reveals a confusing variety of concepts and definitions that hinder biogeographic analysis. Use of this twofold scheme and its subsequent variants should be­discontinued in favour of the more detailed divisions proposed here. Major biogeographical entities of the Shallow-Sea and Open-Sea Realms, separated by the shelf-slope break, are both further subdivisible into Tropical, Temperate and Cold Domains. In the Cold domains, faunal differences between the two Realms and their subdivisions are not easily discernible, since biofacies zones and different habitats were highly condensed. Faunal differences are amplified in the tropical regions, where the North American Midcontinent Province and North Atlantic Province were originally defined. Recognition of endemic taxa is essential for finer classification within domains of the Shallow-Sea Realm (SSR). Our preliminary analysis of Early Ordovician conodont distribution identifies the Laurentian Province (in the Tropical Domain), Australian­(Tropical Domain), North China (Tropical Domain), South China (Temperate Domain), Argentine Precordillera (Temperate Domain) and Balto-Scandian Province (in the Cold Domain). The Open-Sea Realm (OSR) is dominated by cosmopolitan and widespread taxa, and formal subdivision at provincial level is yet to be achieved. The North Atlantic Province encompasses both the Open-Sea Realm and the Temperate and Cold Domains of the Shallow-Sea Realm. The North American Midcontinent Province sensu stricto is more or less equivalent to the Laurentian Province, representing shallow-water regions fringing Laurentia; in a broader sense the North American Midcontinent Province includes all provinces of the Tropical Domain within the Shallow-Sea Realm.

Some 2379 conodont specimens have been recovered from 50 samples through the 560 m thick BowanPark Group and the basal part of the Malachi's Hill Beds of Late Ordovician age, from the western side of the Molong high, in central New South Wales. These have been assigned to 32 species including three new species, Panderodus nodus nov. sp., Paroistodus? nowlani nov. sp. and Yaoxianognathus ani nov. sp., and a revised multielement apparatus of the species, Yaoxianognathus? tunguskaensis ( Moskalenko ). Two stratigraphically distinct conodont assemblages characterised by the first appearances of T. blandus and T. tumidus, respectively, are recognised. They are correlated with similar faunas in the mid-upper part of the Cliefden Caves Limestone Group and the lower Malongulli Formation of the eastern Molong High in central New South Wales. The Bowan Park fauna as a whole is dominated by Panderodus gracilis ( Branson & Mehl ), Yaoxianognathus ani nov. sp., Belodina confluens Sweet , Protopanderodus liripipus Kennedy, Barnes & Uyeno and Drepanoistodus suberectus ( Branson & Mehl ) (72% of total fauna), and shows a mixture of North American Midcontinent and North China affinities. However, influx of some species of North Atlantic Realm aspect mainly occurs in the T. tumidus assemblage which, exhibiting a significant increase in diversity, is preserved in a relatively deeper water facies.