Conodont Species Research Articles

Early Permian and Permian–Triassic boundary interval conodonts from the Central Qiangtang metamorphic belt, northern Tibet, and their paleobiogeographic and paleoclimatic implications

The >500-km-long Central Qiangtang metamorphic belt (CQMB), northern Tibet, offers valuable materials for studying the tectonic evolution and paleobiogeography of the Qiangtang Block. In this study, two conodont faunas (the Mesogondolella and Clarkina–Hindeodus–Isarcicella faunas) are reported for the first time, from the Jiaomuri area of the CQMB. The Mesogondolella fauna, including M. siciliensis, M. qiangtangensis, and?M. sp., is from the exotic limestone blocks at the Jiaomuchaka 2 and Jiangaizangbu sections, indicating a late Kungurian age (Cisuralian, Early Permian). A total of 20 conodont species from five genera are identified and two conodont biozones are established in the Clarkina–Hindeodus–Isarcicella fauna at the Jiaomuchaka 1 section. In addition, the Borinella nepalensis horizon is also recognized at the present section. Based on the conodont succession, the Permian–Triassic boundary (PTB) is temporarily placed between the Clarkina yini and Isarcicella staeschei zones. The late Kungurian Mesogondolella fauna belongs to a transitional zone between the warm- and cool-water conodont provinces and is slightly different from faunas in the southwestern part of the South Qiangtang Block (SQB). A potential explanation for this phenomenon is that the SQB may have undergone anticlockwise rotation during northward-drifting, and warm-water currents along the northern peri-Gondwanan margin may have played a crucial role in conodont distribution. The absence of coeval cool-water Vjalovognathus and M. idahoensis in the CQMB and the southern part of the SQB suggests a weak paleobiogeographical affinity with the Lhasa Block, eastern Myanmar, and Western Australia. In the Clarkina–Hindeodus–Isarcicella fauna of the PTB interval, the co-existence of the endemic species C. sosioensis and warm-water Iranognathus may indicate that the SQB drifted to equatorial regions and had a close relationship with Iran. In addition, the existence of Borinella confirms that the genus preferred relatively cool-water habitats in the Induan–Olenekian boundary (IOB) interval.

Global pattern of conodont similarity and faunal constraints during the highstand of the Evae eustatic event (late Floian, Lower Ordovician)

One of the largest Ordovician sea-level rises is the Evae transgression, which occurs in the lower part of the Oepikodus evae Biozone, indicative of a late Floian age. Specifically, the characteristics associated with the highstand of this event included: a higher proportion of specimens of the index species O. evae than other species, a diversity acme in the evae Biozone, and a reduction of biogeographic barriers that resulted in a high proportion of species with cosmopolitan distribution. In the present contribution, the pattern of species similarity among Laurentia, Argentine Precordillera, Baltica, Kazakhstania, South China, and Australia is evaluated with a multiple coefficient analysis including only the sections that recorded the highstand of the Evae transgression. Moreover, the effect of possible terrestrial, latitudinal, physicochemical barriers and palaeogeographic distance on the species distribution is statistically analysed. Our results show a global pattern of conodont species distribution that is highly constrained by the tested palaeoenvironmental factors. This suggests that contrary to what was expected for a prominent transgression, faunal barriers did not decrease significantly during the Evae drowning peak.

Conodonts suggest a late Spathian (late Early Triassic) age for Thaisaurus chonglakmanii (Reptilia: Ichthyosauromorpha) from Thailand

The timing of the emergence of marine reptiles following the Permian–Triassic mass extinction is crucial for studying the recovery of marine ecosystems in the Triassic. Conodonts, key index fossils in the Triassic, are widely used to date the marine reptiles, especially in the Early Triassic. Triassospathodus anhuinensis is a conodont species originally discovered in the upper Spathian of South China, but lacked a comprehensive description, leading to misidentifications and confusion in previous research. Here, we reevaluated Tr. anhuinensis and summarized its morphological characteristics and spatial and temporal distribution based on a review of the literature. We then critically evaluated the age of the primitive ichthyosaur Thaisaurus chonglakmanii from Thailand based on the updated knowledge of Tr. anhuinensis. We sampled the Khao Thong section where T. chonglakmanii was found for conodont study. Tr. anhuinensis elements were obtained from the bed where T. chonglakmanii was collected and also in the bed five metres above the T. chonglakmanii fossil horizon, suggesting a late Spathian age for T. chonglakmanii. A late Spathian age for T. chonglakmanii questions the hypothesis of Thailand as the place of origin of ichthyosaurs in the late Induan or early Spathain.

Icriodus multidentatus sp. nov. and I. quartadecimensis sp. nov.—New Conodont Species from the Frasnian Stage of the Southern Timan

Icriodus multidentatus sp. nov. and I. quartadecimensis sp. nov.—New Conodont Species from the Frasnian Stage of the Southern Timan

Biostratigraphy and facies around the D/C boundary interval of the Tuye-Darvar section, Eastern Alborz Range, NE Iran

The 1st order mass extinction at the Devonian/Carboniferous transition, known as the Hangenberg Crisis, is characterized by major transgressive/regressive cycles which led to widespread ocean anoxia during the Hangenberg Black Shale Event, as well as to a global major sea-level fall and the worldwide deposition of regressive Hangenberg Sandstone equivalents. The Devonian/Carboniferous transition at the Tuye-Darvar section in the eastern Alborz Range is studied in terms of conodont biostratigraphy, litho-, microfacies and sequence stratigraphy. In order to examine the biostratigraphical framework, forty conodont samples were systematically taken from the studied interval. Thirty-two conodont species belonging to ten genera led to the discrimination of twelve conodont zones, ranging from the Pseudopolygnathus granulosus Zone to the Scaliognathus anchoralis-Doliognathus latus Zone. Due to facies, the conodont record also exhibits some hiatuses. Field observations and sedimentological and microfacies studies led to the identification of thirteen facies types from sub-tidal environments to the fully marine environments, including seven microfacies types. The sediments deposited in a mixed carbonate-siliciclastic platform, revealed four third-order sequences. The Hangenberg Black Shale is not recorded in the Tuye-Darvar section as a result of depositional facies. In comparison with other studied Devonian/Carboniferous Boundary (DCB) sections of the central and northern Iran, the Tuye-Davar section suggests a tectonic position, which is most likely placed on a separate tectonic block.

Palmatolepis abramovae sp. nov.—A New Conodont Species from the Makarovo Regional Substage (Lower Famennian, Upper Devonian) of the Western Slope of the South Urals

Palmatolepis abramovae sp. nov.—A New Conodont Species from the Makarovo Regional Substage (Lower Famennian, Upper Devonian) of the Western Slope of the South Urals

Ordovician conodont biodiversity analysis from the Precordillera (Argentina): a new insight in the global context of the GOBE

ABSTRACT The rapid diversification of conodonts during the Ordovician has been extensively studied by several authors, each presenting distinct diversity curves for different paleocontinents. This study analyzes trends in conodont biodiversity in the Precordillera region, spanning from the late Tremadocian to the early Sandbian ages. A conodont dataset, incorporating species previously identified in sections across Central and Eastern Precordillera, is utillized. This contribution presents the conodont diversity curve for the Lower to early Upper Ordovician in the Precordillera for the first time. The resulting conodont biodiversity pattern reveals that the initial peak of diversification occurs during the O. intermedius Zone (middle-late Floian). A sharp decline in biodiversity is observed during the Dapingian. Finally, during the early Darriwilian, there is a rise in the diversification of conodont species, reaching a peak in the L. pseudoplaunus Zone. This pattern is also compared to curves from Baltica, South China, North China, and Tarim, showing similar trends among them. The variation in Lower-Middle Ordovician conodont diversity in the Precordillera may be linked to different pulses or events within the ‘GOBE’ (Great Ordovician Biodiversification Event).

Morphological trends across the Norian/Rhaetian boundary within Late Triassic conodonts in western Canada: implications for protracted paleoenvironmental disturbance preceding the end-Triassic mass extinction

AbstractThe Late Triassic conodont species Mockina ex gr. carinata and Mockina ex gr. englandi were exceptionally prevalent among the marine fauna of the Panthalassan realm from the middle Norian through to the Rhaetian. Leading into the complete extinction of conodonts near the Triassic/Jurassic boundary, a significant turnover event occurred in conodont fauna across the Norian/Rhaetian boundary (NRB), with the pectiniform elements of common Rhaetian genera from Tethys exhibiting minimal or absent platforms. This intergeneric trend of platform reduction is not as evident in Panthalassa, where these genera are very rare, but morphometric analyses of M. ex gr. carinata and M. ex gr. englandi specimens from across the Canadian Cordillera demonstrate that comparable shifts in morphology occurred intraspecifically in Panthalassa across the NRB, confirming the global extent of these trends. Pectiniform elements of M. ex gr. carinata display a sequential reduction of platform width from the middle Norian to late Norian to Rhaetian, whereas pectiniform elements of M. ex gr. englandi display a reduction of platform width only from the late Norian to Rhaetian. Specimens of both species that have a mid-platform length to breadth ratio greater than 3:1 are restricted to the Rhaetian. Specimens from the Kennecott Point section on Haida Gwaii, British Columbia, demonstrate that this morphological shift occurred somewhat later than other biostratigraphic proxies for the NRB. The global trend of platform width reduction in many conodont pectiniform elements may reflect a change in primary diet away from hard food sources, perhaps suggesting some degree of carbonate biomineralization suppression beginning around the NRB. This interpretation would support CO2 outgassing as the causal mechanism of the environmental disturbance at the NRB and identify the NRB as a significant turning point for Late Triassic ecosystems, marking the beginning of a protracted, multiphase end-Triassic mass extinction.

Shape diversity in conodont elements, a quantitative study using 3D topography

The flourishment of conodont diversity through the Paleozoic is evidenced by the strong diversification of the shape of the elements composing their feeding apparatus. Among the different elements that compose the feeding apparatus, the platform elements (P1) are the most robust. However, the P1 elements also represent the most posterior dental elements of the apparatus, performing therefore the ultimate stage of food processing before ingestion of the food bowl. Thus, characterizing the shape of these elements across various species of conodonts could be relevant to decipher the diversity of feeding behavior among this group. Here we use topographic indices initially developed for the description of teeth relief (RFI, Slope), orientation (OPCr) and sharpness (ARC, DNE) to discriminate quantitatively P1 element shapes among conodont communities of the Late Famennian from the Montagne Noire Area (south France). We evidence methodological considerations such as voxel size impact on topographic indices that should be imperatively considered before conducing these methods on conodonts. Under several homogeneous conditions, this quantification of shape diversity, even on poorly damaged specimens, could bring new clues for the understanding of P1 elements kinematics and feeding strategies among conodonts.

First record of the late Famennian conodonts in Qamdo, Tibet and their biostratigraphic implications

Based on the conodonts recovered for the first time and some brachiopods, this study revises the age of the Wuqingna Formation in eastern Tibet to a late Famennian, challenging prior Carboniferous classification based on coral assemblages. In this study, conodonts are described for the first time from the Wuqingna Formation on the Wuqingka Mountain near Toba Town, Qamdo City in eastern Tibet. The conodont assemblage contains 6 species/subspecies (including morphotypes within open nomenclature) that belong to three genera. The conodont species Polygnathus cf. perplexus, Po. homoirregularis, Po. wuqingnaensis n. sp. and Scaphignathus peterseni suggest an age of late Famennian, probably the Palmatolepis gracilis manca Zone to the Pa. gr. expansa Zone, for the lower part of the Wuqingna Formation, which was previously assigned to the Carboniferous based on the rugose coral assemblages.

High-resolution conodont unitary association zonations (UAZs) across the Induan-Olenekian boundary (Lower Triassic): A global correlation

A precise global timescale for the Lower Triassic Series is essential to understand the sequence of events following the end-Permian mass extinction. A crucial step toward providing the necessary high-resolution chronostratigraphic framework for this interval is the final resolution of a long debated Global Stratotype Section and Point (GSSP) for the Induan-Olenekian boundary (IOB; Lower Triassic). Lower Triassic conodont biostratigraphy has been studied around the world in the past decades, with significant recent progress in the recognition of evolutionary lineages and new collections leading to a refined definition of the IOB. The worldwide distribution of Novispathodus waageni sensu lato has been proposed as the marker defining the IOB. This study recognized 15 or 9 unitary associations across the IOB interval worldwide depending on the taxa and sections that are utilized. The first analysis comprises 37 conodont species from 31 globally representative sections distributed around circum-Paleotethys and Panthalassic oceans, including South China, West Pakistan, northern India, North America and others. This analysis resulted in 15 unitary associations with the probable IOB being calibrated within UAZ-2. A second analysis involved only 31 taxa from 31 sections with species of four genera (Borinella, Scythogondolella, Paulella and Wapitiodus) removed. This analysis therefore was dominated by species of Neospathodus and Novispathodus that have wide distribution and normally are applied to define the IOB; this analysis only yielded 10 unitary associations with UAZ-2 including species normally considered for defining the IOB. Unitary association analyses are deterministic, providing a single result for a given dataset, but are also very conservative by defining zones based on maximal associations of taxa rather than taxonomic events. As such they cannot define a GSSP, although they can constrain a GSSP-bearing interval. Two sections are currently considered as the candidates for the base-Olenekian GSSP, including the West Pingdingshan section of Chaohu area, Anhui Province, South China and the Mud section near Spiti, northern India. This unitary association analysis indicates that the West Pingdingshan section is the most complete and reproducible site for the GSSP of the IOB based on the first appearances of Eurygnathodus costatus, Neospathodus posterolongatus, Novispathodus waageni eowaageni, and Nv. waageni waageni. They all co-occur in UAZ-2, which is calibrated to a 5 m interval from Beds 23–4 to 25–30 at the West Pingdingshan section, in which the primary markers Nv. waageni eowaageni and Nv. waageni waageni do not appear until upper Bed 24 and lower Bed 25. The same UAZ is confined to Beds 12b to 14a in the Mud section. In addition, two new species: Neospathodus yangtzeensis sp. nov. and Novispathodus shani sp. nov. are described, which will significantly refine the conodont zonations of early-middle Smithian and help to constrain the IOB interval. Owing to global distribution, the well-documented Ns. posterolongatus may serve as an auxiliary marker for the IOB by its first occurrence (FO), and Eurygnathodus costatus approximates the IOB in shallow-water settings.

Middle–Upper Ordovician conodonts from the Gunningbland area in central New South Wales with implications for regional correlations

This study documents Middle to Late Ordovician conodont faunas primarily from the Billabong Creek Formation exposed in the Gunningbland area located west of Parkes and northwest of Forbes in central New South Wales. Forty-four identifiable conodont species recovered from 105 limestone samples in this area form the basis of the most complete biostratigraphic succession in shallow-water facies known through this interval from Australia. Four conodont biozones are recognised, extending from the middle Darriwilian Histiodella holodentata–Eoplacognathus pseudoplanus and Eoplacognathus suecicus biozones, through the upper Darriwilian Pygodus serra Biozone, to the Pygodus anserinus Biozone spanning the uppermost Darriwilian to basal Sandbian interval. A lower to middle Sandbian carbonate gap coincides with an unzoned interval, followed by the successively younger Belodina compressa, Phragmodus undatus and Taoqupognathus blandus conodont biozones in the upper Sandbian to lower Katian. The T. blandus Biozone directly correlates with the detailed conodont biozonation established in Katian limestones of the Molong Volcanic Belt further east. These age determinations provide much improved precision for correlation within Phases 2 and 3 in the mineral-rich Macquarie Volcanic Province. Analysis of conodont biofacies data supports an enhanced understanding of the geological evolution of the Macquarie Volcanic Province by interpreting the interplay between volcanic activity and carbonate deposition. KEY POINTS Conodont studies in the Billabong Creek Formation of the Gunningbland area reveal the only known biostratigraphic succession in Australia that extends continuously from the middle Darriwilian to basal Sandbian. Three Late Ordovician (late Sandbian to early Katian) conodont biozones in the upper Billabong Creek Formation correlate precisely with carbonates of the Molong Volcanic Belt to the east. Revised stratigraphic definitions of the Billabong Creek and Gunningbland formations are provided.

Upper Devonian conodont fauna from Western Hubei, China and its significance

ABSTRACT Pelagic standard conodont biozonation is less applicable to nearshore shallow-water depositional settings close to the peritidal, where it is needed to establish its own conodont zonation. The Upper Devonian Xiejingsi Formation in South China is an important unit for nearshore conodont biostratigraphy investigation as its deposits in the nearshore argillaceous-carbonate mixed facies which yield numerous marine fossils. 25 conodont species belonging to 6 genera of platform elements were described in four sections of this formation in western Hubei, including 9 new species. Based on the conodont distribution in these sections, six nearshore conodont biozones are introduced in ascending order: Polygnathus brevis – Polynodosus changyangensis sp. nov. Assemblage Zone, Icriodus cornutus – Pelekysgnathus arcuatus sp. nov. – Polygnathus brevilaminus Assemblage Zone, Palmatolepis angulata Zone, Palmatolepis angulata – Palmatolepis quadrantinodosalobata Assemblage Zone, Palmatolepis quadrantinodosalobata Zone and Polygnathus planirostratus Zone. The correlation of these biozones with those of pelagic standard ones indicates an age of the Xiejingsi Formation in western Hubei from at least the Frasnian linguiformis Zone to the Famennian Lower rhomboidea Zone. Through constructing nearshore shallow-water conodont biozones based on the establishment of comprehensive conodont succession, this paper provides a case study for high-resolution conodont biostratigraphy investigation in the shallow-water settings.

An endemic conodont fauna of Darriwilian (Middle Ordovician) age from the Santa Gertrudis Formation, southwestern Gondwanan margin and its paleobiogeographic relationships

A large collection of conodonts (over 4200 elements) from the Santa Gertrudis Formation of the Cordillera Oriental, NW Argentina, is analyzed. The mostly endemic fauna of this unit and the lack of index species require complex taxonomic and biostratigraphic interpretations. We determined new species apparatuses by reviewing previous literature with a different taxonomic approach: Erismodus saltaensis n. sp., Erraticodon aldridgei n. sp., Gallinatodus elegantissimus n. gen. et sp., Pyramidens cactus n. gen. et sp., P. spinatus n. gen. et sp., Zentagnathus gertrudisae n. sp. Although the lack of key conodont species for intercontinental correlation precludes biostratigraphic assignment to a particular biozone, the overlapping ranges of recorded species restrict the age range to the upper Lenodus variabilis, Yangtzeplacognathus crassus and the lower Eoplacognathus pseudoplanus zones, of middle Darriwilian age (Dw2, Middle Ordovician). The depositional environment of the Santa Gertrudis Formation is primarily a shallow inner platform influenced by waves but not by storms; its paleogeographic location in mid-high latitudes exerts important control over the conodont biofacies, similar to the Arabian Darriwilian faunas of the Gondwanan margin. A narrow marine seaway along the suture zone connecting East and West Gondwana is proposed to explain the evolution of lineages of shallow cold-water conodont faunas from the Middle Ordovician onwards.

Upper Changhsingian to lower Anisian conodont biostratigraphy of the Datuguan section, Nanpanjiang Basin, South China

The Great Bank of Guizhou (GBG) of South China is an important area for the study of Lower Triassic conodont biostratigraphy, but few studies have concerned the clastic facies of this region. The Datuguan section in Luodian County, southern Guizhou Province, is a typical clastic ramp section, preserving a relatively complete conodont succession from the uppermost Permian to lower Middle Triassic. A total of nearly 4000 P1 elements were obtained from this section, and 48 conodont species belonging to 16 genera have been identified, including a new species, Gladigondolella luodianensis sp. nov. 12 conodont biozones have been recognized, namely, the Clarkina yini Zone, the C. meishanensis Zone, the Hindeodus postparvus Zone, the Novispathodus waageni Zone, the Discretella discreta Zone, the Nv. pingdingshanensis Zone, the Icriospathodus collinsoni Zone, the Triassospathodus homeri Zone, the Tr. symmetricus Zone, the Tr. triangularis Zone, the Tr. sosioensis Zone, and the Chiosella timorensis Zone in ascending order. These conodont zones improve the resolution of correlation with other sections in this region, as well as globally. Based on the conodont successions and correlation of lithology, the Permian–Triassic boundary (PTB) and the Griesbachian–Dienerian boundary (GDB) are temporarily placed at the middle of Bed 8, 7 m below the top of the Linghao Formation, and the top of Bed 12, 15 m above the bottom of the Luolou Formation, respectively. The Induan–Olenekian boundary (IOB), the Smithian–Spathian boundary (SSB), and the Olenekian–Anisian boundary (OAB) are drawn at Bed 15–1, Bed 27–1, and Bed 42–2, in terms of the first occurrences (FOs) of Nv. waageni sensu lato, Nv. pingdingshanensis, and Ch. timorensis sensu stricto respectively. The conodonts and ammonoids from the Datuguan section supplement the materials of the Guandao section, which is an important reference section for the definition of OAB. In addition, the distribution of segminiplanate conodonts from the platform margin to the basin center has been determined in the Nanpanjiang Basin, revealing that segminiplanates migrated to equatorial region four times and preferred a narrow mid-depth setting during relatively cooler periods of the Early Triassic, in addition to occupying the more oxygenated deep-water basin at other time.

The Ladinian–Carnian conodont fauna at Yize, Yunnan, southwestern China, with implications for conodont palaeoecology and palaeogeography

AbstractSubdivisions of Ladinian–Carnian boundary beds and the lower Carnian strata in South China are challenging owing to a paucity of west Tethyan ammonoids. We investigated a conodont fauna in a continuous section at Yize in eastern Yunnan Province to provide a biostratigraphic solution. Five genera and 24 conodont species are recognized, and five conodont zones are established. The zones are, in ascending order, the Paragondolella inclinata Zone, the Quadralella polygnathiformis Zone, the Quadralella praelindae Zone, the Quadralella auriformis Zone and the Quadralella robusta Zone. The Ladinian–Carnian boundary is provisionally defined by the first occurrences of Quadralella polygnathiformis and Quadralella intermedia in the cherty limestone member of the Zhuganpo Formation. Regional correlations via conodont biostratigraphy indicate that the Zhuganpo Formation is probably diachronous, with a maximal range spanning the upper Ladinian to the lower Carnian. Amongst all common late Ladinian – early Carnian conodont genera, Paragondolella, Quadralella and Mazzaella are probably cosmopolitan. Budurovignathus was restricted to a few basins and probably preferred offshore or deep-water environments.

Biostratigraphy and biofacies of the Kasimovian conodonts from the Shanglong section, South China

Abstract Late Moscovian–early Gzhelian conodonts occur abundantly in a newly discovered slope section, the Shanglong section, southern Guizhou, South China. The conodont fauna is dominated by P1 elements of Idiognathodus and associated with elements of Swadelina , Streptognathodus and Heckelina . A total of 62 species, including species in open nomenclature, were identified, which are assigned to eight genera. Index conodont species of Middle and Late Pennsylvanian, e.g. I. podolskensis Group, Sw. sp. A, Sw . subexcelsa , Sw . makhlinae , I . heckeli , I . magnificus , I . guizhouensis , H. eudoraensis , I . naraoensis , and H . simulator are all recovered, and their 10 conodont zones are recognized. The richness and abundance of the conodonts throughout the section are analysed. Conodont richness ranges from 1 to 14 and is positively related to conodont abundance (1–379). The composition of conodont elements, i.e. sinistral v. dextral, P1 v. non-P1 and adult v. subadult and juvenile, is presented. The numerical cluster technique is employed to identify four subbiofacies of the slope setting, namely the I . podolskensis , Swadelina , I. swadei–magnificus and Streptognathodus – Heckelina–Idiognathodus subbiofacies.

Automatic identification of conodont species using fine-grained convolutional neural networks

Conodonts are jawless vertebrates deposited in marine strata from the Cambrian to the Triassic that play an important role in geoscience research. The accurate identification of conodonts requires experienced professional researchers. The process is time-consuming and laborious and can be subjective and affected by the professional level and opinions of the appraisers. The problem is exacerbated by the limited number of experts who are qualified to identify conodonts. Therefore, a rapid and simple artificial intelligence method is needed to assist with the identification of conodont species. Although the use of deep convolutional neural networks (CNN) for fossil identification has been widely studied, the data used are usually from different families, genera or even higher-level taxonomic units. However, in practical geoscience research, geologists are often more interested in classifying species belonging to the same genus. In this study, we use five fine-grained CNN models on a dataset consisting of nine species of the conodont genus Hindeodus. Based on the cross-validation results, we show that using the Bilinear-ResNet18 model and transfer learning generates the optimal classifier. Area Under Curve (AUC) value of 0.9 on the test dataset was obtained by the optimal classifier, indicating that the performance of our classifier is satisfactory. In addition, although our study is based on a very limited taxa of conodonts, our research principles and processes can be used as a reference for the automatic identification of other fossils.

Revision of the Ordovician conodont species Fahraeusodus adentatus and the new genus Pohlerodus

Fahraeusodus adentatus, the type species of Fahraeusodus, is revised based on the re-examination of the original types and a large collection of topotype specimens from the Emanuel Formation (Lower Ordovician) of the Canning Basin in Western Australia. Confirmation of a modified pastinate Pa element in the septimembrate ramiform-pectiniform apparatus of this conodont species has resulted in a redefined generic definition for Fahraeusodus. Based on this newly defined diagnosis of Fahraeusodus and its type species, all other species previously assigned to Fahraeusodus and Texania are reviewed and now placed in Pohlerodus gen. nov., which is erected herein to substitute Texania, which is a junior homonym. Yong Yi Zhen [ yong-yi.zhen@regional.nsw.gov.au ], Geological Survey of New South Wales, W.B. Clarke Geoscience Centre, 947–953 Londonderry Road, Londonderry NSW 2753, Australia.

Ordovician conodonts from the Ban Tha Kradan area, western Thailand

Eleven Ordovician conodont species of nine genera from the Ban Tha Kradan area of western Thailand are described and illustrated here for the first time. Based on similar lithological features and stratigraphical range, the upper part of Tha Manao Formation in the Ban Tha Kradan area of Kanchanaburi Province is amended and assigned to the Pa Kae Formation. The Scolopodus striatus Assemblage Zone is recognized in the revised Tha Manao Formation in the Ban Tha Kradan area. Based on conodonts and macrofossils, the Tha Manao Formation in western Thailand is assigned to the upper Floian to Darriwilian, and the conformably overlying Pa Kae Formation to the Sandbian to lower Katian.