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The Lung Cam expanded stratigraphic succession in Vietnam is correlated herein to the Meishan D section in China, the GSSP for the Permian–Triassic boundary. The first appearance datum of the conodontHindeodus parvusat Meishan defines the Permian–Triassic boundary, and using published graphic correlation, the Permian–Triassic boundary level has been projected into the Lung Cam section. Using time-series analysis of magnetic susceptibility (χ) data, it is determined thatH. parvusarrived at Lung Cam ∼18 kyr before the Permian–Triassic boundary. Data indicate that the Lung Cam section is expanded by ∼90 % relative to the GSSP section at Meishan. Given the expanded Lung Cam section, it is possible to resolve the timing of significant events during the Permian–Triassic transition with high precision. These events include major stepped extinctions, beginning at ∼135 kyr and ending at ∼110 kyr below the Permian–Triassic boundary, with a duration of ∼25 kyr, followed by deposition of Lung Cam ash Bed + 13, which is equivalent to Siberian Traps volcanism is graphically correlated to a precession Time-series model, placing onset of this major volcanic event at ~242 kyr before the PTB. The Meishan Beds 25 and 26, at ∼100 kyr before the Permian–Triassic boundary. In addition, the elemental geochemical, carbon and oxygen isotope stratigraphy, and magnetostratigraphy susceptibility datasets from Lung Cam allow good correlation to other Permian–Triassic boundary succession. These datasets are helpful when the conodont biostratigraphy is poorly known in sections with problems such as lithofacies variability, or is undefined, owing possibly to lithofacies exclusions, anoxia or for other reasons. The Lung Pu Permian–Triassic boundary section, ∼45 km from Lung Cam, is used to test these problems.

We report the first discovery of Lower Triassic Clarkina assemblages: four natural conodont assemblages from Lower Triassic pelagic black claystones of the North Kitakami Belt in northeastern Japan (Akkamori section). The fossils were obtained from the 2.5-m horizon level above the black claystone base, which is assigned to the end-Permian mass-extinction event. This horizon has been dated to the earliest Triassic (Griesbachian) by the occurrence of Hindeodus parvus, which is the index species for the base of the Triassic, in the same and subjacent horizons. These four fossil assemblages include a paired segminiplanate-formed P1 element, which was identified as the genus Clarkina, and have fully or partially preserved the original components of conodont elements. The most complete assemblage among them includes 15 distinctive elements, namely S0 and pairs of M, S1, S2, S3, S4, P1, and P2. It is noteworthy that these fossil assemblages preserve probable impressions of ‘eyes,’ which were replaced by aggregations of silicate, phosphate, and sulphide minerals. The occurrence of several sets of fossils that retain the original positioning of the conodonts' elemental apparatuses, as well as the original presence of soft tissue, may be attributed to the process by which the conodonts' bodies were transported to the deep seafloor, and by which the activity of agents of decomposition was inhibited in near-abiotic sediments under anoxic conditions in the pelagic deep sea during the earliest Triassic.

The Kamura section, located in the Chichibu Belt of Kyushu Island in southern Japan, contains a succession of uppermost Permian to Upper Triassic shallow-marine atoll sediments from the mid-Panthalassic Ocean. In the present study, carbonate microfacies, conodont biostratigraphy, and carbonate carbon isotopes were analyzed, making it possible to construct a detailed biochronological framework for the Triassic of the central Panthalassic region. A total of 14 conodont zones are recognized from the uppermost Changhsingian to the upper Norian. The Lower Triassic contains the Hindeodus parvus, Isarcicella isarcica, and H. postparvus zones (Griesbachian), the Neospathodus dieneri Zone (Dienerian), and the Novispathodus ex gr. waageni-Parachirognathus Zone (Smithian), while no evidence of the upper Lower Triassic Spathian substage was recovered at Kamura. The overlying Middle Triassic section consists of the Chiosella ex gr. timorensis-Cratognathus, ‘Paragondolella’ ex gr. alpina-Pg. ex gr. excelsa, Budurovignathus hungaricus, and B. mungoensis zones, followed in the Upper Triassic by the Quadralella tadpole-Gladigondolella malayensis, Q. lobata-Q. carpathica, Primatella cf. orchardi-Pr. permica, Epigondolella rigoi-‘Pg.’ hallstattensis, and E. ex gr. bidentata-Norigondolella steinbergensis zones. The exact stratigraphic intervals present at Kamura were refined through intercalibration of the conodont biozonation data with its δ13Ccarb profile, which shows a characteristic series of negative and positive excursions that correspond to well-established global reference profiles. The Permian–Triassic boundary is placed 0.20 m above the Mitai-Kamura formation contact (a reference datum corresponding to the end-Permian extinction horizon, = 0 m) based on the first appearance of H. parvus, and the Olenekian–Anisian boundary is placed 17.60 m above the reference datum based on the first appearance of Ch. ex gr. timorensis. Kamura carbonates were assigned to six fabric types and 17 microfacies. The microfacies succession records a deepening immediately following the end-Permian mass extinction, a strong shallowing during the mid to late Smithian, development of an unconformity spanning the entire Spathian, and minor sea-level fluctuations during the Middle and Late Triassic. The Spathian unconformity is attributed to a eustatic fall related to a sharp cooling event at or close to the Smithian–Spathian boundary that exposed the Kamura atoll. The subsequent resumption of shallow-marine sedimentation in the earliest Middle Triassic was probably due to continued thermal subsidence of the oceanic crustal basement beneath the atoll. The present work is the most complete analysis to date of the conodont biostratigraphic, carbon isotope chemostratigraphic, and eustatic records of the Triassic System in the central Panthalassic Ocean and should serve as a regional reference standard in the future.

Molybdenum isotopes are considered to be a promising paleoredox proxy in reducing facies for evaluating either global-ocean redox conditions (given quantitative Mo uptake) or local redox conditions (given non-quantitative Mo uptake). Here, we examine the Mo-isotopic composition of black to gray shales from the Permian-Triassic boundary (PTB) section at Chaohu, eastern China, in order to assess the utility of this proxy under a range of paleoredox conditions. We evaluated local redox conditions using a combination of redox-sensitive trace-element concentrations (Mo, U) and FeT/Al ratios, recognizing six intervals of more reducing conditions at the PTB and Induan-Olenekian boundary (IOB), in the mid-Smithian, at the Smithian-Spathian boundary (SSB), and in the mid- and upper Spathian. These six intervals are associated with variably weak to moderate enrichments of Mo, and they show variable shifts away from background δ98Mo values of ca. −0.4 to +0.1‰ (recording detrital Mo-isotopic compositions) toward δ98Mo values as high as +2.3 ± 0.2‰. Based on an analysis of local redox proxies versus δ98Mo as well as of sample-to-sample variance in δ98Mo values, we conclude that only one of the six reducing intervals in the study section is likely to record contemporaneous seawater δ98Mo (as a result of quasi-quantitative Mo uptake), i.e., the interval from the Hindeodus typicalis conodont Zone close to the PTB, for which δ98Mo values of +2.3 ± 0.2‰ suggest average global-ocean redox conditions similar to those of the modern ocean. For the remaining five reducing intervals, non-quantitative Mo uptake led to Mo-isotope signatures reflecting local, mostly suboxic redox conditions. The highest Mo concentrations (17–23 ppm) were yielded by the mid- and upper Spathian intervals, and the lack of concurrent U enrichment in the mid-Spathian interval suggests the local operation of a Mn-Fe particulate shuttle, an inference that is consistent with its relatively low δ98Mo values (0 ± 0.3‰). The lack of evidence for strong oceanic anoxia in the South China Craton following the PTB crisis may have been a factor in the relatively rapid recovery of marine ecosystems in this region during the Early Triassic. The present contribution serves as a case study of the application of Mo-isotopes as a paleoredox proxy in low-[Mo] sediments, which requires a careful assessment of the relative importance of global versus local redox influences based on additional proxies and evaluation criteria.

We present recent study results of the Lower Triassic conodont succession from the Ganxi and Jianshi areas of Enshi city, western Hubei Province, South China, which were situated on a carbonate ramp at the northeastern margin of the Upper Yangtze Platform. Therein, the uppermost Permian to Lower Triassic succession is well exposed and yielded abundant conodonts. A total of nine conodont zones are differentiated: (1) Clarkina yini Zone, (2) Clarkina meishanensis Zone, (3) Hindeodus changxingensis Zone, (4) Hindeodus parvus Zone, (5) Hindeodus postparvus Zone, (6) Clarkina planata Zone, (7) Neoclarkina aff. discreta Zone, (8) Neospathodus dieneri Zone, and (9) Novispathodus waageni Zone. The Ns. dieneri M1, Ns. dieneri M2, and Ns. dieneri M3 Subzones have also been distinguished within the Ns. dieneri Zone, and the Nv. waageni eowaageni and Nv. waageni waageni Subzones are recognizable within the Nv. waageni Zone in Jianshi. Most of the zones occur in succession, but the C. planata Zone is a local ecozone reflecting deeper water biofacies during H. postparvus Zone time. In the Jianshi section, the Permian–Triassic boundary is placed at Bed 136-2 based on the appearance of Hindeodus parvus immediately above the disappearance of Changhsingian taxa, while the Induan–Olenekian boundary (IOB) is drawn at Bed 225 + 40 cm based on the first appearance of Nv. waageni eowaageni within the upper range of the Ns. dieneri Zone indices. The Enshi conodont zones overall correlate well with those recognized elsewhere in South China and worldwide.

Two Permian-Triassic boundary (PTB) sections (Pojue and Dala) are well exposed in an isolated carbonate platform (Napo Platform) on the southwestern margin of the Nanpanjiang Basin, South China. These sections provide an insight into the transition across the PTB and a detailed investigation of the conodont biostratigraphy and inorganic carbon isotopes is presented. The PTB at the Pojue Section is placed at the base of Bed 10B (a dolomitized mudstone found below a microbialite horizon), defined by the first occurrence of Hindeodus parvus. At the Dala Section, four conodont zones occur. They are, in ascending order, the Hindeodus parvus Zone, Isarcicella staeschei Zone, Isarcicella isarcica Zone and Clarkina planata Zone. Comparison with the Pojue Section suggests the PTB at Dala also occurs at the base of dolomitized mudstone below a microbialite horizon, although the first occurrence of Hindeodus parvus is near the top of a microbialite bed: an occurrence that is also seen in other platform sections. The succeeding microbialite beds developed during the ongoing PTB mass extinction phase. This time was characterized by low carbon isotope values, and a microbialite ecosystem that provided a refuge for selected groups (bivalves, ostracods and microgastropods) that were likely tolerant of extremely high temperatures.

A single sample from the logged section at eastern side of Gua Panjang limestone hill, southwest of Kampung Kubang Rasa Village, Merapoh, has yielded 5 very important conodont species. They are Hindeodus parvus erectus, Hindeodus parvus parvus, Hindeodus latidentatus latidentatus, Hindeodus latidentatus praeparvus, Hindeodus postparvus, Hindeodus eurypge and Isarcicella staeschi. These Early Triassic conodonts were obtained in a bioclastic dolostone sample, located 2.5 m above bioclastic grainstone which yielded Late Permian foraminifera. The conodonts found were given Conodont Alteration Index (CAI) scale of 5, consistent with the heating of Main Range granitoid during Indosinian Orogeny. Limestone harbouring basal Triassic conodonts in Gua Panjang is interpreted to be deposited in an open shallow marine shelf environment.

[First paragraph] AGEMATSU et al. (2018) commented on our recent paper about testing hypotheses of element loss and apparatus stability in the apparatus composition of complex conodonts (Zhang et al. 2017). They take issue not with our approach, but with our specific hypothesis concerning the skeletal apparatus of Hindeodus parvus. We proposed that,in marked contrast to the remarkable anatomical conservatism exhibited by ozarkodinid conodonts, which seem not to vary their 15 element ‘dental formula’ over a period in excess of 250 million years, H. parvus had only 13 elements, lacking 2 elements from the posterior P domain of the apparatus.Our paper presents an hypothesis of homology for the skeletal elements of H. parvus that Agematsu et al. (2018) argue is incorrrect, based on three lines of reasoning

A major discrepancy for the age of the Selong Group from middle Cisuralian (Early Permian) to Changhsingian resulted from previous reports of Sakmarian, Kungurian and Guadalupian (Middle Permian) conodonts and Lopingian (Late Permian) brachiopods. Recently, Cisuralian and Guadalupian conodonts were reported again from the Selong Group and the basal part of the Kangshare Formation at the Selong section, but the age discrepancy remains. We present our conodont materials based on large samples collected from the Selong Group and our interpretation based on identifications using a sample population approach. Three conodont zones are recognized in our re-investigation of the upper part of the Selong Group. They include the Vjalovognathus sp., the Mesogondolella hendersoni, and the M. sheni zones, in ascending order. These zones are overlain by the basal Triassic Hindeodus parvus Zone and the Otoceras woodwardi Zone. Our reassessment of conodonts reported by previous studies from Selong and nearby sections suggest that all specimens consistently point to a Lopingian age; the upper part of the Selong Group is latest Changhsingian in age based on the presence of Clarkina orchardi and Mesogondolella sheni. Previously reported early Cisuralian and Guadalupian conodonts are misidentified using a form species concept. A hiatus may be present at the erosional surface between the Selong Group and the Waagenites Bed of the basal part of the Kangshare Formation. However, the hiatus is minimal because conodont and brachiopod assemblages above and below this surface are very similar, and it results from a latest Changhsingian transgression just before the extinction that follows a global latest Changhsingian regression. There is a distinct rapid end-Permian mass extinction at Selong within the Waagenites Bed, as indicated by the disappearances of all benthic brachiopods, rugose corals and Permian bryozoans. The burst of Clarkina species in the Waagenites Bed and throughout the entire Lower Triassic at Selong is interpreted as a southward migration of equatorial conodont animals associated with the rapid global warming beginning at the end of the Permian. The cool- or cold-water species of Mesogondolella, in the upper part of the Selong Group and the basal part of the Kangshare Formation, are representative of the uppermost Permian in the bipolar/bi-temperate cold-water province and are not reworked from the underlying Selong Group or any other unknown Cisuralian or Guadalupian deposits.

The Permian Period is punctuated by Earth system changes unlike any other in geological history. The start of the Permian witnessed the termination of the Late Paleozoic Ice Age, followed by the climatic transition from icehouse to greenhouse conditions. The Guadalupian-Lopingian (Middle-Late Permian) was characterized by two biocrises associated to volcanisms: (i) the end-Guadalupian crisis and (ii) the end-Permian mass extinction. Seawater Sr isotope (87Sr/86Sr) records can shed light on the evolution of the Permian Earth system. The Permian 87Sr/86Sr record suffers from a number of issues including low resolution and potential diagenetic alteration. In this paper, we summarize the existing Permian 87Sr/86Sr records and focus on the current challenges. We also present a new, high-resolution Permian 87Sr/86Sr curve derived from pristine brachiopod shells based on data resulting from careful diagenetic screening. Our new record shows that the 87Sr/86Sr of seawater decreased continuously from the earliest Permian to the middle Capitanian (late Guadalupian), with the lowest ratio of 0.706832 registered in the Colania douvillei-Kahlerina pachiytheca Zone. Subsequently, 87Sr/86Sr ratios increased from the late Capitanian to the latest Permian and reached a ratio of 0.707167 just 0.8 m below the first occurrence of the Hindeodus parvus. We employed a stochastic oceanic box model to explore the potential drivers of the Permian seawater Sr isotope record. Our results support that changes in the hydrothermal input, rather than changes in continental weathering intensity, are the most likely controlling factor for the observed variations in Permian seawater 87Sr/86Sr. Therefore, we suggest that the marine hydrothermal system (and hence ocean basin dynamics and deep-sea temperatures) may have been the driver of the pronounced decreasing 87Sr/86Sr trend across the Permian.

The Permian–Triassic boundary (PTB) is defined by the conodont Hindeodus parvus at Meishan section D in the palaeotropical Tethyan region, where basal Triassic ammonoids are rare and poorly preserved. Here we describe some basal Early Triassic ammonoids from the lower part of the Kangshare Formation at the Qubu section in the Mt. Everest area in southern Tibet, China. Our study recognizes three distinct ammonoid zones, the Otoceras woodwardi, Ophiceras tibeticum, and Ambites zones in ascending order. The occurrence of Otoceras, a key basal Triassic taxon, is here documented for the first time in this area. The first occurrence of Triassic conodonts at Qubu indicates that the PTB is not higher than the level 0.81 m above the base of the dolomite unit of the Kangshare Formation, and the first occurrence of the ammonoid Otoceras woodwardi is 0.89 m higher up at the section. At Qubu, the Griesbachian–Dienerian boundary is placed between the Ophiceras tibeticum Zone and the Ambites Zone. Our work represents a valuable addition for the construction of a high resolution of Griesbachian and Dienerian ammonoid biozonations in southern Tibet and provides a framework for the basal Triassic correlation in the Mt. Everest area.

Understanding the timing and correlation of significant global events in Earth history is facilitated by the Global Boundary Stratotype Section and Point (GSSP) concept, along with multi-proxy correlation techniques. As an example, the Permian–Triassic boundary (PTB) GSSP is used herein to correlate three PTB successions in east and southeast Asia. The PTB is defined using the First Appearance Datum (FAD) of the conodont Hindeodus parvus at the Meishan D section in China. By definition then, Meishan D is the only section on Earth where the FAD of H. parvus represents the beginning of the Triassic, at ~ 251.88 Ma, and thus the end of the Permian. Therefore, when correlating strata in any other section back to the PTB using biostratigraphic data, the local Lowest Observed Occurrence Point (LOOP) of H. parvus will probably not equate precisely to the defined FAD GSSP level (the PTB) for the beginning of the Triassic at Meishan D. The Graphic Correlation method, applied to PTB sites in China and Vietnam, is used herein to demonstrate that LOOPs of H. parvus in other successions are not equivalent in time to the PTB FAD. The LOOP and Highest Observed Occurrence Point (HOOP) for conodont data at two other successions studied, Huangzhishan in China, and Lung Cam in Vietnam, are used to determine the approximate level where the Triassic begins in these successions, resulting in high-resolution correlation among the sections and correlation back to the PTB GSSP level. It is demonstrated that when critical biostratigraphic data are missing, multiple proxy correlation techniques, geochemical, geophysical and, in some regional instances, unique lithostratigraphic information such as coeval ash beds, can be used to aid in locating the boundary in successions that are not the defining GSSP. LOOP and HOOP data are used to establish a Line of Correlation to differentiate between a defining PTB H. parvus FAD versus the H. parvus LOOP in secondary successions, and to project the PTB FAD into secondary sections to define the PTB at these localities. In addition, the timing of H. parvus arrivals at these sections is used to establish rough dispersal rates and patterns in the region.

Earliest Triassic natural conodont assemblages preserved as impressions on bedding planes occur in a claystone of the Hashikadani Formation, which is part of the Mino Terrane, a Jurassic accretionary complex in Japan. In this study, the apparatus of Hindeodus parvus (Kozur and Pjatakova, 1976) is reconstructed using synchrotron radiation micro-tomography (SR–μCT). This species has six kinds of elements disposed in 15 positions forming the conodont apparatus. Carminiscaphate, angulate, and makellate forms are settled in pairs in the P1, P2, and M positions, respectively. The single alate element is correlated with the S0 position. The S array is a cluster of eight ramiforms, subdivided into two inner pairs of digyrate S1–2 and two outer pairs of bipennate S3–4 elements. The reconstruction is similar to a well-known ozarkodinid apparatus model. In addition, the μCT images show that the ‘anterior’ and ‘posterior’ processes of the S1–2 elements faced the caudal and rostral ends of the living conodont body, respectively.

Knowledge of the conodont skeleton, in terms of the morphology of the elements and the positions they occupy, provides the foundation for understanding of homology, taxonomy and evolutionary relationships in conodonts. This knowledge also underpins analyses of conodont functional morphology and feeding. Direct evidence of skeletal anatomy and apparatus architecture comes from natural assemblages: fossils that preserve together the articulated remains of the conodont apparatus, either collapsed onto a bedding plane or as clusters of elements in which juxtaposed and overlapping elements have been fused together by diagenetic minerals. Here we describe six clusters of the biostratigraphically important conodont Hindeodus parvus from the Lower Triassic Shangsi section, Sichuan Province, South China. Five of these clusters represent the partial remains of articulated skeletons, providing direct evidence of the number and arrangement of elements in the apparatus. Combined with data from previously published natural assemblages this provides a test of the hypothesis that Triassic conodonts had a reduced dentition. Hindeodus parvus possessed a complete raptorial array of two M and nine S elements (unpaired S0; symmetrically paired S1, S2, S3, S4); the paired P1 locations were occupied by carminiscaphate elements, but the apparatus lacked P2 elements. This is consistent with broader evidence for a particularly high degree of integration and constraint operating on the S–M array of morphologically complex conodonts, leading to conserved architecture of the array over a period of more than 250 million years. The loss of elements from the P domain implies a change in food processing ability and, given the predominance of data from P elements in conodont taxonomy and biostratigraphy, the hypothesis of element loss from the P domain has significant implications for the broader understanding of conodont diversity and evolutionary patterns.

Conodonts and ammonoids have played significant roles in the Permian-Triassic timescale. In order to uncover the nature of the Permian-Triassic mass extinction and subsequent recovery, we studied conodont and ammonoid biostratigraphies around the Permian-Triassic boundary from Jianzishan of Hubei, South China. A total of four conodont zones and two ammonoid beds are recognized. In ascending order, the conodont zones are Late Changhsingian Clarkina changxingensis Zone, Clarkina yini Zone and Griesbachian Hindeodus parvus Zone, Hindeodus postparvus Zone; the ammonoid beds are Late Griesbachian Ophiceras beds and Early Dienerian Ussuridiscus varaha beds. At Jianzishan, Ophiceras beds are stratigraphically younger than Hindeodus parvus Zone, but it is likely to be the same level with Hindeodus postparvus Zone. The Lower Dienerian in Bed 8 in this section is characterized by ammonoid Ussuridiscus varaha beds, which is associated with many Late Griesbachian conodonts including Hindeodus postparvus, Hindeodus praeparvus, Hindeodus typicalis, Hindeodus pisai, Hindeodus latidentatus, Hindeodus parvus, Hindeodus anterodentatus and Isarcicella turgida, indicating these conodont species could pass through the Griesbachian-Dienerian boundary and occurred in the Early Dienerian oceans.

Permian strata from the Tieqiao section (Jiangnan Basin, South China) contain several distinctive conodont assemblages. Early Permian (Cisuralian) assemblages are dominated by the genera Sweetognathus, Pseudosweetognathus and Hindeodus with rare Neostreptognathodus and Gullodus. Gondolellids are absent until the end of the Kungurian stage—in contrast to many parts of the world where gondolellids and Neostreptognathodus are the dominant Kungurian conodonts. A conodont changeover is seen at Tieqiao and coincided with a rise of sea level in the late Kungurian to the early Roadian: the previously dominant sweetognathids were replaced by mesogondolellids. The Middle and Late Permian (Guadalupian and Lopingian Series) witnessed dominance of gondolellids (Jinogondolella and Clarkina), the common presence of Hindeodus and decimation of Sweetognathus. Twenty main and seven subordinate conodont zones are recognised at Tieqiao, spanning the lower Artinskian to the middle Wuchiapingian Stage. The main (first appearance datum) zones are, in ascending order by stage: the Sweetognathus (Sw.) whitei, Sw. toriyamai, and Sw. asymmetrica n. sp. Zones for the Artinskian; the Neostreptognathodus prayi, Sw. guizhouensis, Sw. iranicus, Sw. adjunctus, Sw. subsymmeticus and Sw. hanzhongensis Zones for the Kungurian; the Jinogondolella (J.) nankingensis Zone for the Roadian; the J. aserrata Zone for the Wordian; the J. postserrata, J. shannoni, J. altudaensis, J. prexuanhanensis, J. xuanhanensis, J. granti and Clarkina (C.) hongshuiensis Zones for the Capitanian and the C. postbitteri Zone and C. transcaucasica Zone for the base and middle of the Wuchiapingian. The subordinate (interval) zones are the Pseudosweetognathus (Ps.) costatus, Ps. monocornus, Hindeodus (H.) gulloides, Pseudohindeodus ramovsi, Gullodus (G.) sicilianus, G. duani and H. excavates Zones. In addition, three new species, Gullodus tieqiaoensis n. sp., Pseudohindeodus elliptica n. sp. and Sweetognathus asymmetrica n. sp. are described. Age assignments for less common species (e.g., G. duani, H. catalanoi and Pseudosweetognathus monocornus etc.) are reassessed based on a rich conodont collection.

The well-exposed stratigraphic sequences on the Great Bank of Guizhou (GBG) in South China provide important information for the understanding of various environmental settings during the Permian-Triassic mass extinction and the subsequent recovery, including one of the oldest Triassic marginal reef complexes, which is viewed as an important indicator of biotic recovery following the end-Permian mass extinction. Here we report a systematic conodont study on a newly exposed Lower-Middle Triassic section, the Mingtang section, at the margin of the GBG to provide more data for the time scale of the post-extinction recovery. Twenty-four species in 11 conodont genera are identified and assigned to Hindeodus parvus , Neoclarkina discreta , Neospathodus dieneri , Novispathodus waageni , Neospathodus triangularis - Triassospathodus homeri , Chiosella timorensis , Nicoraella germanica , and Nicoraella kockeli zones in ascending order. These zones correlate well with the conodont successions in South China and over the world. The Induan-Olenekian boundary can be well defined by the first occurrence of Novispathodus waageni in the lower-middle part of the Luolou Formation, while the Early-Middle Triassic boundary was placed at 0.2 m below the top of the Luolou Formation according to the first occurrence of Chiosella timorensis . These conodont data suggest that the Tubiphytes -reef began to recover in the Bithynian (early Middle Triassic), later than benthonic organisms such as foraminifers and calcareous algae.

The Middle Siberian volcanic plateau is characterized with respect to its paleoecological environments. In this area, volcanism commenced in the Severodvinian (Vishkilian) Age. The lower (tuffaceous) part of the plateau section (Lebedev deposits) was formed in the Vyatkian Age. Its middle (tufflava) part (Khungtukun deposits) is correlative with the Goudikeng Formation (interval of 65–111 m) in the Dalongkou type section of China and corresponds to the Quadrocladus pachyphyllus ... Echinolimnadia mattoxi Zone. The top of this sedimentary unit (111 m up from the base of the Goudikeng Formation) should be correlated with the base of the Otoceras Ecozone. The upper (lava) part of the plateau (Putorana deposits) corresponds to the interval of 111–210 m, belongs to the Elatocladus linearis ... Cornia vosini Ecozone, and is older than the Hindeodus parvus Zone, which is now considered as the basal unit of the Triassic marine sequences. The volcanic plateau section shows now evidence of any biotic crisis.

The biochronological characterization of the Permian–Triassic boundary (PTB) is here improved by means of conodont unitary associations zones (UAZs). The selected data set comprises the six best documented sections in South China, including the Meishan global stratotype section and point of the PTB. This new biochronological zonation has a much higher accuracy than previous schemes, which were based on continuous interval zones. We show how traditional interval zones around the PTB in South China suffer from diachronous boundaries that cross each other as the result of sampling effort (intensity and density) and of geographical or ecological exclusion of zonal index taxa, inclusive of the first occurrence of the base Triassic index species Hindeodus parvus . Our quantitative and robust approach produces a discrete sequence comprising six UAZs. In the closest agreement with the position of the PTB in Meishan, the PTB falls here in the interval of separation between UAZ 2 and UAZ 3 . In Meishan, this interval of separation corresponds to the stratigraphic interval above bed 25 and below bed 27, which also includes the formational boundary between the Changhsing and the Yinkeng formations. We provide a new and independent support for this placement by showing that it correlates with the main turnover of conodont species within the analysed time interval. As previously documented, the main extinction interval ranged from bed 25 to bed 28 in Meishan, which are here assigned to UAZ 2 and to UAZ 4 , respectively. Therefore, the main extinction episode is not of end-Permian age but straddles the PTB. Previous claims for two distinct extinction pulses bracketing the PTB in South China were based on traditional conodont interval zones and are not supported by the new UA zonation. The oldest Triassic UAZ 3 is identified by the characteristic species Hindeodus pisai and by any of the ten characteristic pairs of species Neogondolella zhejiangensis or Neogondolella tulongensis associated with Hindeodus changxingensis , Hindeodus parvus , Neogondolella planata , Neogondolella taylorae or Isarcicella huckriedei . Separate analyses of anchignathodontids and neogondolellids sub-data sets show that the base of the Triassic is unambiguously defined by the occurrences of the characteristic species H. changxingensis , Isarcicella prisca , and I. huckriedei in shallow-water settings, and of two characteristic species, N. planata and N. taylorae , in deep-water settings. Moreover, we document uncoupled diversity trends across the PTB for each of these two clades. A substantial diversification phase of anchignathodontids spans the interval from UAZ 3 to UAZ 5 . It is followed by a drastic (50%) reduction of the number of species between UAZ 5 and UAZ 6 . On the other hand, neogondolellids show a protracted extinction from UAZ 4 to UAZ 6 . In South China, correlations are proposed for the microbialite-bearing sections and deeper-water PTB sections. The UA method also highlights which parts of the conodont record are still insufficiently documented for reliable correlations. Biochronological correlations with Meishan and its U–Pb radio-isotopic ages allow inferring a maximal duration of 61 ± 48 ka for the gap at the base of the Triassic microbial limestone at Dajiang, a time interval that also corresponds to the duration of the main extinction episode in Meishan.

In many tropical shallow water regions the end-Permian mass extinction event occurs at the top fossiliferous packstone beds and is immediately followed by the development of microbialite facies. Both the age and redox conditions of the microbialite have been debated and both factors are addressed here in a study of the Gaohua section (Cili County, Hunan Province, China): specifically the size distribution of pyrite framboids and high-resolution conodont biostratigraphy. The framboids populations show a broad size range with examples up to 30 microns in diameter, and indicating dysoxic but not anoxic depositional conditions. More intense dysoxia is recorded in interbedded laminated micrites but not beds of giant ooids. Both the Hindeodus parvus zone and Isarcicella isarcica zones were established with the microbialite beds being confined to the H. parvus zone. Therefore, the formation of microbialite postdates the end Permian main mass extinction and records oxygen-poor conditions even in a shallow-water setting such as Gaohua section at Cili.

We report herein new Permian conodont data from the strata of the La Cueva Limestone and the Mina Mexico Formation in central Sonora. These data allow us to characterize the biostratigraphy of the southwestern Laurentian Permian successions and the last stage of the Ouachita-Marathon-Sonora orogen in northwestern Mexico. We studied three sections in central Sonora, which cover the stratigraphic contact between both formations. In the Las Rastras Section (LRS), we recognized a conodont association that includes Neostreptognathodus exsculptus sensu Henderson and McGugan, Sweetognathus “whitei”, Sw. subsymmetricus, and Hindeodus aff. H. minutus at its base and Sw. subsymmetricus, Hindeodus aff. H. gulloides, Gullodus tieqiaoensis, and Mesogondolella siciliensis at its top. These conodonts date the upper part of the La Cueva Limestone as latest early to earliest late Kungurian and the lower part of the Mina Mexico Formation as late Kungurian in the LRS. In the Sierra Martinez 1 and 2 sections (SMS-1 and SMS-2), located 7 km to the east of the LRS, the conodont association points to an age corresponding to the latest early to earliest middle Kungurian for both La Cueva Limestone and Mina Mexico Formation. This association is represented by the species Ns. exsculptus sensu Henderson and McGugan and Sw. subsymmetricus. The stratigraphic contact between both formations has been interpreted as the beginning of the autochthonous deformation of the Laurentian platform. This new conodont data allows us to associate this event to the latest early–earliest middle Kungurian in SMS-1 and SMS-2, and to the late Kungurian in the LRS showing a diachrony between these localities. This diachrony may be related to the continental oblique collision of Laurentia against Gondwana that resulted in progressively younger basins westward along the Ouachita-Marathon-Sonora orogen. This diachrony can also be due to the configuration of the subsiding Mina Mexico foredeep, which would have produced a non-coeval contact in the areas closer to the thrust front and those located far from it.

Conodont biostratigraphic and high-precision U-Pb isotope data are presented for the Permian-Triassic transition in three limestone hills, Gua Bama, Gua Panjang and Gua Sei, in the Malay Peninsula. Gua Bama yielded conodonts representating the Clarkina orientalis, Clarkina wangi and Clarkina subcarinata zones and the Wuchiapingian-Changhsingian stage boundary is identified for the first time in Malaysia. The Wuchiapingian subspecies Hindeodus julfensis wardlawi Kozur is elevated to species level, H. wardlawi, and evolved to the Changhsingian species Hindeodus julfensis Sweet and then Hindeodus changxingensis Wang. Distinguishing features and a new phylogeny of species of the genera Hindeodus and Isarcicella in the Late Permian-Early Triassic are presented. A new CA-TIMS high-precision U-Pb age of 253.70 ± 0.06 Ma for zircon from a tuff layer 6.5 m above the Wuchiapingian-Changhsingian boundary and in the lower part of the Clarkina subcarinata zone is reported. Conodont faunas from Gua Panjang represent the Clarkina changxingensis-Hindeodus praeparvus, Clarkina yini-Clarkina zhangi, and Hindeodus parvus zones and the PTB is placed at approximately 12 m in the studied 19 m thick sequence. Three tuff layers in the lower part of Gua Panjang contain zircon grains with CA-TIMS U-Pb ages of 252.23 ± 0.07 Ma, 252.47 ± 0.12 Ma and 252.16 ± 0.16 Ma (maximum age), respectively. Conodont faunas from Gua Sei represent the Upper Permian (Changhsingian) Clarkina hauschei - Hindeodus latidentatus Zone and the basal Triassic lower Induan (Griesbachian) Hindeodus parvus and Isarcicella staeschei zones. The PTB is placed at 30 m above the base of the Gua Sei sequence.

Research on the Permian-Triassic boundary (PTB) along the northern margins of Pangaea (exposed today in the Arctic region) has been heavily reliant on field observations, where data resolution was consequently determined by outcrop condition and accessibility. Core drilling in central Spitsbergen allowed for a near-complete recovery of two ~90 m cores through the PTB. Analyses of the core and nearby outcrops include stratigraphic logging and sampling, XRF scanning, petrography, biostratigraphy, isotope geochemistry, and geochronology. The First Appearance Datum (FAD) of H. parvus in Svalbard places the base of the Triassic ca. 4 m above the base of the Vikinghøgda Formation, and ca. 2.50 m above the End-Permian Mass Extinction (EPME) and its associated sharp negative δ13C. The PTB therefore falls within the Reduviasporonites chalastus Assemblage Zone in Svalbard. Precise U-Pb TIMS dating of two zircon crystals in a tephra layer just above the first documented Hindeodus parvus in Svalbard gives an age of 252.13 ± 0.62 Ma. High-resolution palaeoenvironmental proxies, including Si/kcps (kilo counts per second), Zr/Rb, K/Ti, Fe/K, and V/Cr, indicate a transition towards a more arid climate in the earliest Triassic, contemporaneous with prolonged bottom-water dysoxic/anoxic conditions, following an increase in volcanic activity in the Late Permian. Statistical analysis of Zr/Rb, K/Ti and V/Cr elemental ratios suggests that the system was impacted by long-eccentricity (400 kyr) cyclicity. The δ13C excursion in organic carbon (δ13Corg) record signals a large negative carbon isotope excursion (CIE) associated with the mass extinction event, but also records a second, smaller negative CIE ca. 22 m above this interval. This younger δ13Corg excursion correlates to similar CIEs in the Dienerian (late Induan) records of other sections, notably in the Tethys Ocean, which have been interpreted as recording a small biotic crisis during the post-extinction recovery. Evidence of this negative CIE in Spitsbergen suggests that the Dienerian crisis may have been global in extent. The negative δ13Corg values are associated with evidence for dysoxia or anoxia in the core, and the occurrence of tephra layers in the same interval suggests a possible connection between the Dienerian crisis and a discrete episode of volcanic activity. A new high-resolution stratigraphic and palaeoenvironmental record spanning the End-Permian Mass Extinction and its aftermath in central Spitsbergen, Svalbard publishedVersion

Unitary Association Method (UAM) analyses of conodont faunas from 28 sections spanning the biggest Phanerozoic end-Permian mass extinction and significant global environmental and ecosystem perturbations during the succeeding Early Triassic are presented. Based on 72 conodont species, 26 Unitary Association Zones (UAZs) are established for the latest Permian to earliest Middle Triassic of South China. These UAZs provide quantitative high-resolution tools to correlate sequences in the Early Triassic of South China and to compare and test high-resolution conodont biostratigraphy based on interval conodont zones developed over the past three decades. Our quantitative analyses provide insights on ongoing debates relating to the First Appearance Datum (FAD) of the conodont Hindeodus parvus which is used to place and subsequently correlate the “Golden Spike” defining the base of the Triassic (Permian-Triassic Boundary) at the base of Bed 27c at the GSSP Meishan D Section. Previous proposals that suggested potential earlier occurrences of H. parvus below its FAD at Meishan section are not supported by our results. In deep water sections, the First Occurrence (FO) of H. parvus lies at the base of UAZ 5 at the Bianyang section while it lies within UAZ 6 at the Meishan section. This indicates that the earliest occurrence of H. parvus in South China is in the Bianyang section but this conclusion needs further testing due to the reliance on “spot” data by the UAM. Anomalously high occurrences of Hindeodus in the Mingtang section (close to the Bianyang section) further suggests that the Bianyang-Mingtang area may have provided a temporally extended habitable zone for anchignathodontid conodonts. Stage boundaries currently proposed or established using interval conodont zones locate within or between UAZs and are difficult to correlate with carbon isotope curves. UAZs are useful in helping to define GSSPs by recognizing which correlations are most robust and in the selection of the most appropriate species and level for GSSPs.

Early Triassic microbialites are distributed widely in the shallow marine facies of the Tethys Region, especially in the carbonate platform where they were deposited immediately after the latest Permian mass extinction (LPME). Ten Griesbachian domed microbial mounds were found in an outcrop of the uppermost first member of the Feixianguan (FXG) Formation at Baimiaozi, which is located in Beibei in the Upper Yangtze Region of southwest China. Field investigations and thin-sections analyses indicated that oolitic limestone, bioclastic limestone, microbialite, marl, and mudstone deposits are present in the first and second members of the FXG Formation, among which the thickness of the microbial mound above the massive oolitic limestone at the carbonate platform was approximately 3-4 m. Three facies were identified at the microbial mounds, namely, a mound base, mound body, and mound cap. Irregular laminae were found in the brown-colored microbialite of the mound base. The main mound body, which is composed of gray microbialite, is 1.0-1.5 m high and 2.0-3.0 m in diameter at the base. Dark gray grainstone found in the mound cap is covered by a thin layer of shelly limestone containing intact fossils of bivalves and gastropods, which are indicative of a simple ecosystem consisting of microbes and primary consumers. Brown-colored mudstone and marl layers of the second member of the FXG Formation overlie the microbialite, and this indicates that growth of the microbial mounds was halted by a sudden increase of terrestrial inputs and rapid transgression. Early Griesbachian conodonts of Hindeodus parvus? were identified from the mound limestone and the overlying strata of the second member of the FXG Formation, which is suggestive of the presence of a microbialite-dominated ocean in the Upper Yangtze Region during a certain interval after the LPME.

Upper Permian and lowermost Triassic strata of the Masore section in western Slovenia have been restudied by means of bio- and lithostratigraphy. This section is mainly characterized by a carbonate succession of the Bellerophon Formation deposited in a shallow marine ramp environment that was located in the western part of the Paleotethys. The Permian-Triassic boundary (PTB) transition is marked by laminated microbialites – stromatolites interpreted to reflect a deeper ramp environment. The conodont elements recovered enabled the recognition of the Hindeodus praeparvus Zone of the uppermost Permian (Upper Changhsingian) in the Bellerophon Formation. Gondolellids are documented in the PTB transitional interval with microbial microfacies, whereas the Isarcicella isarcica Zone (Lower Griesbachian, Lower Triassic) is recognized in the tectonically separated Werfen Formation just above the microbial microfacies part of the section. The lowermost part of the microbialites is characterized by Late Permian species of foraminifers indicating that at least this part of the section is still Upper Permian.

During and after the end Permian mass extinction terrestrial and marine biota underwent major changes and reorganizations. The latest Permian and earliest Triassic is also characterized by major negative carbon isotope shifts reflecting fundamental changes in the carbon cycle. The present study documents a high-resolution bulk organic carbon isotope record and palynofacies analysis spanning the latest Permian–earliest Triassic of East Greenland. An almost 700 meter thick composite section from Kap Stosch allowed discriminating 6 chemostratigraphic intervals that provide the basis for the correlation with other coeval records across the world, and for the recognition of basin wide transgressive–regressive events documenting tectonic activity during the opening of the Greenland–Norway Basin. The identification of the main factors that influenced the organic carbon isotope signal during the earliest Triassic (Griesbachian to Dienerian) was possible due to the combination of bulk organic carbon isotope, palynofacies and Rock-Eval data. Two negative carbon isotopic shifts in the Kap Stosch record can be correlated with negative shifts recorded in coeval sections across the globe. A first negative shift precedes the base of the Triassic as defined by the first occurrence of the conodont Hindeodus parvus in the Meishan reference section, and the second one coincides with the suggested Griesbachian–Dienerian boundary. This new organic carbon isotope record from the extended Kap Stosch section from the Boreal Realm documents regional and global carbon cycle signals of the interval between the latest Palaeozoic and the onset of the Mesozoic.

The Tibetan Plateau, the highest plateau in the world, is relatively difficult to access. Therefore, the stratigraphy and fossils in this area are poorly known, although they are very important for interpreting the palaeogeographical evolution of different tectonic blocks. Here we report the new discovery of an abundant conodont fauna from the lowest part of the Xiala Formation in the central part of the Lhasa Block, Tibet. This conodont fauna includes three genera and four species (Mesogondolella idahoensis, M. siciliensis, Vjalovognathus nicolli Yuan, Shen & Henderson sp. nov. and Hindeodus sp.). The conodont fauna indicates that the lowest part of the Xiala Formation is late Kungurian in age based on the presence of abundant Mesogondolella idahoensis and the denticle characters of Vjalovognathus nicolli sp. nov. The presence of the conodont genus Vjalovognathus, the associated small solitary corals and the absence of any fusulinids clearly suggest a cool-water condition in the lower part of the Xiala F...

The Guryul Ravine section (Kashmir, India) exposes one the world's most continuous carbonate rock successions throughout the Permian-Triassic boundary and beyond. Due to political instability in this region, the biostratigraphy of this section has not been updated for nearly three decades. Following new high-resolution sampling, we reassess here the conodont biochronology and isotopic records of the fifteen lowermost stratigraphical metres (Member E) of the Khunamuh Formation at Guryul Ravine section. This interval includes both the Permian-Triassic and the Griesbachian-Dienerian (lower-upper Induan) boundaries. The First Occurrence of Hindeodus parvus, the index for the base of the Triassic, is confirmed in the middle of sub-member E2 (Unit 56 in Matsuda, 1981 [Journal of Geosciences, Osaka City University 24, 75–108]; our bed GUR09). We characterize 11 Unitary Association Zones based on the conodont record from China and from Guryul Ravine. UAZ1–2 are Late Permian and identified only in South China, UAZ3–11 are identified both in China and Guryul Ravine. The Griesbachian-Dienerian boundary is included within the interval of separation between UAZ8 and UAZ9. At Guryul Ravine, this boundary is precisely constrained between beds GUR310 and GUR311, and corresponds to the replacement of segminiplanate (here Clarkina and Neoclarkina) by segminate (Sweetospathodus and Neospathodus) conodonts. This faunal turnover was possibly linked to a climate change at the Griesbachian-Dienerian transition, from a cool and dry to a hot and humid climate. This transition could be the trigger of the migration of neogondolellids towards high latitudes and of the radiation of neospathodids during the Dienerian.

Accurate and precise dating of individual volcanogenic beds that spread across multiple sedimentary successions is a powerful tool to untangle stratigraphic age contradictions, since these horizons are deposited synchronously. In this study, we show that combining apatite chemistry with zircon age, Th/U ratio, and Hf isotope composition leads to reliable lateral correlation of volcanic horizons across sections representing disparate biological, chemical, and physical paleoenvironments. We correlate two volcanogenic horizons across six sedimentary sections straddling the Permian-Triassic boundary (PTB) in the Nanpanjiang Basin (South China), including the last Permian bed below the unconformity in shallow-water sections of the Luolou Platform. We place the PTB in our sections at the marked lithological change in order to avoid the difficulties that arise from the diachronism of the index conodont Hindeodus parvus, the first occurrence of which defines the PTB at the Global Stratotype Section and Point at Meishan. Our new data demonstrate that these volcanogenic beds are contemporaneous and cogenetic, allowing us to pool high-precision U-Pb zircon ages from the same horizon across several sections, and dating the last Permian volcanic event in this basin at 252.048 ± 0.033 Ma. We show that the mineral chemistry of apatite and zircon of intra- and interbasin-wide volcanogenic beds provides tie points against which biozones, carbon isotopes, astronomic cycles, and geomagnetic polarity time series can be stringently tested.

Meishan Section D with the Wuchiapingian/Changhsingian and Permian/Triassic GSSPs has become the most intensively studied section because it records the whole process of the largest biological extinction during the Phanerozoic. Numerous data including high-precision geochronology, multiple isotope chemostratigraphy, magnetostratigraphy, and high-resolution multiple fossil biostratigraphy have been determined during the last decade. Conodonts are very abundant in the Changhsingian Stage at the Meishan sections and their biostratigraphy together with geochronologic and multiple geochemical data provide a basic temporal framework to calibrate the end-Permian mass extinction and realize global correlation between sections at Meishan and those in other regions of the world. However, major discrepancies exist in various previous studies of conodonts from the Meishan sections. Many different authors have documented very different species ranges based on different concepts and approaches of taxonomy. We here employ a sample population approach to revise and refine the high-resolution conodont biostratigraphic framework for the Changhsingian Stage and end-Permian mass extinction interval across the Permian–Triassic boundary (PTB) at the Meishan sections. Eight zones are recognized from the latest Wuchiapingian to the basal Triassic. They are, in ascending order, the Clarkina longicuspidata Zone in the uppermost Wuchiapingian; the Clarkina wangi Zone, Clarkina subcarinata Zone, Clarkina changxingensis Zone, Clarkina yini Zone, Clarkina meishanensis Zone, Clarkina zhejiangensis–Hindeodus changxingensis Zone in the Changhsingian Stage, and the Hindeodus parvus Zone in the basal Triassic. Conodont evolutionary lineages for the whole Changhsingian are also tentatively established. All species are described in detail and growth series of different specimens for valid species are figured as completely as possible. The temporal relationship of each conodont zone with geochemical excursions, geochronologic calibration and magnetostratigraphical polarity zones are provided, which is critical to understand the tempo of the end-Permian mass extinction.

The Permian–Triassic boundary interval in shallow shelf seas of South China shows Upper Permian limestones overlain by lowermost Triassic microbialites. Global sea-level rose across the Permian–Triassic boundary, but an irregular top-Permian erosion surface across a 10 km north–south transect of the Great Bank of Guizhou contains evidence of sea-level fluctuation. The surface represents the ‘event horizon’ of mass extinction, below the biostratigraphic Permian–Triassic boundary defined by first appearance datum of conodont Hindeodus parvus. An Upper Permian foraminiferal grainstone beneath this surface contains geopetal sediments, etched grains, and pendent and meniscus cements interpreted here as vadose. However, these latter diagenetic processes occurred before the event horizon and were followed by erosion of the final Permian surface. This erosion cuts previous fabrics but lacks evidence of weathering or bioerosion. A few centimetres below is an earlier grainstone that was also eroded but lacks proof of sub-aerial processes. Samples therefore reveal one, or possibly two, small-scale relative sea-level changes before the Triassic transgression in this area, and these may relate to local tectonics. The final Permian surface is subject to at least four interpretations: (i) sub-aerial physical erosion and dissolution by carbon dioxide-enriched fresh water or carbon dioxide-enriched mixed water, prior to Triassic transgression; (ii) sub-aerial physical erosion overprinted by dissolution related to carbon dioxide-enriched sea water in the Early Triassic transgression; (iii) submarine dissolution affected by acidified sea water due to rapid increase in volcanically-derived carbon dioxide and oxidized methane released from marine clathrates; (iv) submarine dissolution due to acid anoxic waters rising across the continental shelf, unrelated to atmospheric carbon dioxide or oxidized methane. Field and petrographic evidence suggests that (i) is the simplest option; and it is possible that (ii) and (iii) occurred, but none are proved. Option (iv) is unlikely given the evidence and modelling of supersaturation of upwelled waters with respect to bicarbonate.

The Providence Limestone member of the Dugger Formation in Indiana and its lithologic correlatives in the southern part of the Illinois Basin are thin lime mudstones to packstones lying stratigraphically between the Herrin and Hymera Coal Members of the Dugger Formation and their equivalents. The purposes of the study are to describe and correlate the Providence conodont fauna and to apply biofacies analysis and petrographic study to interpreting the paleoenvironments.Providence conodonts are dominated by representatives of the Idiognathodus-Streptognathodus plexus. Hindeodus is abundant; Neognathodus is common; and Idioprioniodus, Adetognathus, and Diplognathodus are common only in some sections. Aethotaxis is a minor constituent.Conodont biofacies reflect a shallow, nearshore, low- to moderate-energy marine environment. The Idiognathodus-Streptognathodus plexus indicates quiet to moderately elevated energy levels. Hindeodus replaces part of the Idiognathodus-Streptognathodus plexus in higher energy conditions. Diplognathodus has an affinity for low to slightly elevated energy conditions. Migration during ontogeny to quite, organic-rich water from a more open, slightly higher energy environment is indicated for Streptognathodus oppletus.Assignment to the Neognathodus dilatus-N. roundyi zone indicates a middle Desmoinesian age. The new species Diplognathodus indianaensis is morphologically intermediate between the early Desmoinesian D. coloradoensis and the late Desmoinesian D. illinoisensis and allows refinement of a Diplognathodus-based zonation.

Nine assemblages of conodont elements have been found on bedding surfaces of the “Wolfcamp Shale’ from the Midland Basin, Texas. Four of these assemblages have Pa elements assigned to Sweetognathus cf. S. inornatus. The assemblages are classified taphonomically as apparatus (remains or partial remains of a single individual) or coprolitic associations. The two apparatus assemblages indicate that Sweetognathus cf. S. inornatus possessed a seximembrate apparatus comprised of Pa, Pb, M, Sa, Sb, and Sc elements. Five of the seven coprolitic associations contain numerous elements (50–100) and/or multiple pairs of Pa elements representing the presumably ingested remains of two or more conodonts.The “Wolfcamp Shale’ assemblages are significant because 1) they confirm the polygnathacean affinity of the family Sweetognathidae, 2) they represent the youngest polygnathacean assemblages currently known, and 3) they permit comparison of multielement Sweetognathus with homologous elements of coeval genera such as Hindeodus, Adetognathus, Streptognathodus, and Neostreptognathodus.