Triassic Conodonts Research Articles

First Records of Late Triassic Conodont Fauna and δ13Ccarb from the Dengdengqiao Section, Dangchang County, Gansu Province, Northwestern China

Based on a study of 49 conodont and 57 geochemical samples from the Upper Triassic, carbonate-dominated Dengdengqiao Formation, Qinling Basin, China, the Carnian conodonts and carbon isotope records are first reported. Two genera and four species have been identified amongst 87 conodont elements: Mosherella praebudaensis, Mo. longnanensis sp. nov., Mo. sp., and “Misikella” longidentata. The presence of Mo. praebudaensis indicates that the lower part (bed 2) of the formation is attributable to the Julian (lower Carnian) substage. A radiolarian fauna identified in a previous study belongs to the upper Carnian, but the sampling horizon is unclear. The δ13Ccarb curve shows a ∼1.8‰ negative excursion beginning from upper part of bed 3, but its stratigraphic location is uncertain. The Dengdengqiao Formation is clearly at least partly of Carnian age but could include younger strata. The abundant calcareous algae at the section is probably due to some transport rather than preserved in site. The unusual ecosystem with rare marine organisms may reflect long-term stressful and unfavorable conditions at Dengdengqiao.

Carbon isotope chemostratigraphy and conodont biostratigraphy around the Smithian–Spathian boundary in the Panthalassan carbonate succession (SW Japan)

Abstract The Tahogawa Member of the Triassic Taho Formation in Southwest Japan consists predominantly of light, dark, and brownish gray bedded limestones and contains abundant Lower to Middle Triassic conodonts. The late Smithian to early Spathian sequence of the Tahogawa Member is divided into five conodont zones, in ascending order: Novispathodus ex gr. waageni, Nv. pingdingshanensis, Nv. brevissimus, Triassospathodus symmetricus, and Tr. homeri. The Scythogondolella milleri Subzone of the Nv. ex gr. waageni Zone contains a late Smithian Anasibirites bearing ammonoid bed. The carbon isotope (δ13Ccarb) curve for the late Smithian to early Spathian shows a rapid excursion with values increasing from ~0.11‰ to ~5.88‰ (VPDB). The rise in δ13Ccarb starts in the upper part of the Nv. ex gr. waageni Zone and continues into the overlying Nv. pingdingshanensis Zone. The δ13Ccarb values peak in the Nv. pingdingshanensis Zone at 5.88‰, and subsequently decrease to 1.13‰ in the Tr. symmetricus Zone. The carbon cycle perturbation recorded in the Tahogawa Member corresponds to the late Smithian to early Spathian global carbon isotope positive and following negative excursions reported from the Tethyan, Panthalassan, and Boreal regions. The Smithian–Spathian boundary is probably located within the Nv. pingdingshanensis Zone of the Tahogawa Member, coincident with the decreasing limb of the carbon isotope perturbation. The combination of δ13Ccarb and conodont stratigraphic data enable us to correlate between the eastern Tethys and Panthalassan regions.

A database of Triassic conodonts from a comprehensive revision of literature

The revision of a comprehensive amount of bibliography has made possible the development of a database containing the stratigraphic ranges of the conodont species from the uppermost Permian and the Triassic, with a total of 336 species in 52 genera. This database is aimed at biostratigraphy and studies related to biological, evolutional and palaeodiversity dynamics

Late Triassic (late Carnian-early Norian) conodonts discovered from the Takisawa limestone body in the Chichibu Composite Belt, Hamamatsu, Shizuoka, central Japan

Late Triassic (late Carnian-early Norian) conodonts discovered from the Takisawa limestone body in the Chichibu Composite Belt, Hamamatsu, Shizuoka, central Japan

Upper Permian and Lower Triassic conodonts, high-precision U-Pb zircon ages and the Permian-Triassic boundary in the Malay Peninsula

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.

Microstructure of Triassic conodont Pseudofurnishius murcianus van den Boogaard: Functional implications

Pseudofurnishius murcianus van den Boogaard is a Triassic conodont with a very characteristic morphology, a blade with a rostral platform heavily denticulated, that makes it easily distinguishable from other coeval species. It is a well-know taxon that has been the object of several palaeobiological works, focused on their apparatus reconstruction, ontogeny and, recently, their P1 element function. In order to increase our palaeobiology knowledge of this taxon we undertook a histological analysis to corroborate the functional hypothesis established for this conodont. The histological study demonstrated the presence of different microstructural types, suggesting that they are functional adaptions due to the slicing function that the P1 elements performed

New biostratigraphic framework for the Triassic–Paleogene in the Neo-Tethys realm of southern Xizang (Tibet), China

Abstract Multifaceted biostratigraphic work on Triassic to Paleogene strata in southern Xizang (Tibet), western China, in the last decades allows a new, refined biochronostratigraphic framework in the Qinghai–Xizang plateau region. Synthesis of the latest biostratigraphic progress is carried out in this paper to build a new integrated biostratigraphic scheme comparable to the international Geological Time Scale. The scheme incorporates key fossils as many of each system, such as ammonites, calcareous nannofossils, conodonts and foraminifers. Other fossil groups that are helpful for stratigraphic division and interregional correlation are also contained. These include bivalves, miospores and radiolarians, some of which, e.g. radiolarians and miospores, not previously well explored, are now utilised for new zones. Biostratigraphic zones of this new integrative system, especially the Lower Triassic conodonts and ammonites, uppermost Triassic–Lower Jurassic ammonites, Upper Cretaceous planktonic foraminifers and calcareous nannofossils, correlate well with the international standards. The results are tabulated as four new comprehensive biostratigraphic charts, which, we hope, will provide a new and more reliable chronostratigraphic foundation for study of Neo-Tethys.

Significance of Early Triassic conodont zones from Western Australia

Significance of Early Triassic conodont zones from Western Australia

Evaluating tectonic models for the formation of the North American Cordillera using multivariate statistical analysis of Late Triassic conodont faunas

The tectonic processes that led to the current configuration of the Quesnel and Stikine terranes within the North American Cordillera are contentious, with competing models favouring either northward, strike-slip movement or southward, rotational movement of the Stikine terrane. Multivariate statistical analysis of Late Triassic conodonts faunas from Canada and the USA has been used to evaluate these competing models and to constrain the movement of terranes relative to the North American continent. Late Carnian to early Norian conodonts are present in both the Stikine and Quesnel terranes, as well as at high and low latitudes on the North American continental margin, in northeastern British Columbia and Nevada respectively. The conodont faunas from each of these four geographic areas have been compared using the Dice, Jaccard, Ochiai and Simpson similarity indices. The highest values of similarity were found to be between the faunas of the Stikine and Quesnel terranes, supporting previous conclusions that these belonged to a single volcanic arc system. The conodont faunas of both of these terranes were more similar to that of northeastern British Columbia than either were to that of Nevada, suggesting that during the Late Triassic the terranes were more likely located at higher latitudes than lower latitudes. Finally, the conodont fauna of the Stikine terrane was significantly more similar to that of Nevada than the fauna of the Quesnel terrane was, which indicates that of the two terranes, the Stikine terrane lay farther south than the Quesnel terrane during the Late Triassic. This interpretation of the orientation of these terranes supports tectonic models that favour northward strike-slip translation of the Stikine terrane, rather than those models that require southward rotation of the terrane.

New biostratigraphic evidence of Late Permian to Late Triassic deposits from Central Tibet and their paleogeographic implications

AbstractTriassic deposits in the Bangong-Nujiang Suture Zone are important for understanding its tectonic nature and evolutionary history, but have not been systematically studied due to a lack of biostratigraphic data. For a long time, the Upper Triassic Quehala Group featuring clasolite has been regarded as the only rocky unit. In recent years, the silicite-dominated Gajia Formation that bears radiolarian fossils was suggested to represent Ladinian to Carnian deposits. The Upper Permian and Lower Triassic rocks have never been excavated and thus are considered to be absent. This research, however, reveals that fossils aged from the Late Permian to Anisian of the Middle Triassic and Norian of the Late Triassic have been preserved in the central Bangong-Nujiang Suture Zone, which provides evidence of Upper Permian to early Middle Triassic deposits and provides new insights on the Upper Triassic strata as well. A new Triassic strata succession is thus proposed for the Bangong-Nujiang Suture Zone, and it demonstrates great similarities with those from Lhasa to the south and Qiangtang to the north. Therefore, we deduce that the Bangong-Nujiang Suture Zone was under a similar depositional setting as its two adjacent terranes, and it was likely a carbonate platform background because limestones were predominant across the Triassic. The newly acquired biostratigraphic data indicate that Lhasa and Qiangtang could not have been located on two separate continents with disparate sedimentary settings; therefore, the Bangong-Nujiang Suture Zone likely did not represent a large ocean between them. This conclusion is supported by lithostratigraphic and paleomagnetic research, which revealed that Lhasa and Qiangtang were positioned at low to middle latitudes during the Early Triassic. Combining this conclusion with fossil evidence, we suggest that the three main Tibetan terranes were in the same palaeobiogeographic division with South China, at least during the Latest Permian to Early Triassic. The Early Triassic conodont species Pachycladina obliqua is probably a fossil sign of middle to low latitudes in palaeogeography.

Latest Wuchiapingian to Earliest Triassic Conodont Zones and δ13Ccarb Isotope Excursions from Deep-Water Sections in Western Hubei Province, South China

Deep-water facies sections have advantages of recording complete information across the Permian-Triassic boundary (PTB). Here we present a detailed study on the conodont biostratigraphy and carbon isotope profile ranges from the Wuchiapingian-Changhsingian boundary (WCB) to the PTB of two deep-water facies sections at Zhuqiao and Shiligou in the Middle Yangtze region, western Hubei, South China. Fifteen species and three genera are identified. Eight conodont zones are recognized, in ascending order, they are the Clarkina orientalis, C. wangi, C. subcarinata, C. changxingensis, C. yini, C. meishanensis, Hindeodus parvus and Isarcicella isarcica zones. The onset of deposition of the deep-water siliceous strata of the Dalong Formation in western Hubei began in the Late Wuchiapingian and persisted to the Late Changhsingian. Carbon isotope negative excursions occur near both the WCB and PTB in both sections. The WCB δ13Ccarb negative excursion is in the C. orientalis and C. wangi zones. The PTB δ13Ccarb negative excursion began in the C. yini Zone and extended to the I. isarcica Zone. The absence of several Changhsingian zones may indicate the difficulty of extracting conodonts from siliceous strata or the presence of an intra-Changhsingian hiatus.

The last phase of conodont evolution during the Late Triassic: Integrating biostratigraphic and phylogenetic approaches

For the Upper Triassic, conodonts are the primary tools utilized in biostratigraphic investigations. For an effective biostratigraphic zonation, the species should be constrained by clear phylogenetic relationships, in which the stratigraphic ranges and taxonomy are reliable. Unfortunately, a phylogenetic framework for the Late Triassic pectiniform conodonts is almost missing, except for particular intervals, such as the Carnian/Norian boundary. The purpose of this study is to examine the latest Norian and Rhaetian pectiniform conodonts in detail in an attempt to determine their phylogenetic relationships, by applying novel phylogenetic methodologies that incorporate both morphological and stratigraphic data. This work is based on the conodont assemblages from the Upper Triassic strata of the Lagonegro Basin (southern Apennines, southern Italy) and the Csővár area (north-central Hungary), complemented with data from the literature. The calibrated phylogenetic analysis of the latest Norian and Rhaetian conodonts supports a two-step evolutionary history: a first radiation (~211–210 Ma) of the Parvigondolella species and the first representative of the genus Misikella, followed by a second phase (~206.5–205 Ma) leading to the final radiation of the Misikella species. Furthermore, the systematic revision of uppermost Triassic conodonts is provided along with the description of Misikella kolarae n. sp.

Exceptional basal-body preservation in some Early Triassic conodont elements from Oman

Conodont elements are composed of two main parts: the crown and the basal body. The basal body of a conodont element is a laminated structure that is less densely mineralized than the crown and, as a result, is rarely preserved. Elements with preserved basal bodies are found only in exceptional cases in the fossil record. To date, no S or M element with preserved basal body has ever been documented for post-Devonian conodonts, which had raised the question of an evolutionary trend towards unmineralized basal bodies in conodonts. Here we report the discovery, in Smithian (Early Triassic) rocks of Oman, of neospathodid conodont elements whose basal body is partly preserved. We demonstrate the presence of basal body in all elements, including S and M elements, of Novispathodus, and most likely of all gondolelloideans, thereby suggesting that the absence of basal bodies in post-Devonian conodonts was due to a preservational bias only. We further demonstrate that the morphology and extent of the basal bodies in Novispathodus are in agreement with previous predictions and do not contradict a cyclostome-like functional model of the apparatus. Based on a review of the occurrences of basal bodies in the literature, we suggest a general pattern for the morphology of the basal bodies in conodont elements that may reflect the mechanical constraints associated with feeding motions.

Middle Triassic conodont apparatus architecture revealed by synchrotron X-ray microtomography

The composition of conodont apparatuses is crucial for understanding the feeding mechanisms of these early vertebrates. However, the multielement apparatus reconstructions of most species remain equivocal because they have been inferred from loose element collections, guided by knowledge from rare articulated ‘bedding plane assemblages’ and fused clusters, often from distantly related taxa. Even these natural assemblages can be difficult to interpret because the component elements can be closely juxtaposed or embedded in matrix, making it hard to discern the morphology of each element and their relative positions within the architecture of the feeding apparatus. Here we report five exceptionally preserved conodont clusters from the Middle Triassic Luoping Biota, Yunnan Province, Southwest China. These materials were scanned using synchrotron radiation X-ray tomographic microscopy (SRXTM), revealing the morphology and positional homology of the component elements in the fused clusters. We confirm that the apparatus of Nicoraella was composed of eight types of elements, comprising a total of 15 elements. SRXTM reveals the positional homologies of the component elements, viz. a single alate element is located in the S0 position, flanked successively abaxially by pairs of breviform digyrate S1 and S2 elements, bipennate S3 and S4 elements, and a pair of inwardly curved breviform digyrate M elements. Carminate elements occupy the P1 and P2 positions. The apparatus of Nicoraella is among the most completely characterised of all conodonts and serves as a template for the reconstruction of gondollellids.

Early Triassic Conodonts from the Tahogawa Member of the Taho Formation, Ehime Prefecture, Southwest Japan

The Triassic Taho Formation crops out in Taho, Shirokawa Town, Seiyo City, Ehime Prefecture, Southwest Japan. The formation is newly divided into the Tahogawa and Sakuragatouge members. The Tahogawa Member consists mainly of partly dolomitized light-, dark-, brownish-gray and black bedded limestones, and yields abundant Early to Middle Triassic conodonts, ammonoids, gastropods, bivalves, brachiopods and fish remains. The Sakuragatouge Member is dominated by brownish gray lenticular conglomeratic limestone and massive gray and white limestones that contain Middle to Late Triassic conodonts, gastropods, bivalves, echinoids and fish remains. In the Tahogawa Member, conodont assemblages are composed of 13 genera and 45 species, including three new species: Neospathodus arcus Maekawa sp. nov., Novispathodus shirokawai Maekawa sp. nov., and Nv. tahoensis Maekawa sp. nov. The member is divided into five conodont zones in ascending order: the Ns. dieneri Zone, the Ns. cristagalli Zone, the Nv. ex gr. waageni Zone, the Nv. pingdingshanensis Zone and the Nv. brevissimus Zone. The Nv. ex gr. waageni Zone contains three conodont subzones (the Eurygnathodus costatus Subzone, the Guangxidella bransoni Subzone and the Scythogondolella milleri Subzone), and the Nv. brevissimus Zone includes the Icriospathodus collinsoni Subzone. The conodont biostratigraphy of the member indicates a late Dienerian to early Spathian age, and correlates with that of Tethyan and Panthalassean sections. The Induan-Olenekian boundary is indicated by the first occurrence of Nv. ex gr. waageni. The Smithian-Spathian boundary is immediately below or intercalated within the Nv. pingdingshanensis Zone.

A Taxonomic Re-Assessment of the Novispathodus waageni Group and Its Role in Defining the Base of the Olenekian (Lower Triassic)

Lower Triassic conodont biostratigraphy has been well studied around the world in the past decades, but the Induan-Olenekian boundary (IOB) remains undecided. The Novispathodus waageni group has been taxonomically re-assessed based on abundant new materials from the Jianshi and Chaohu sections, South China. New study shows that Nv. waageni typically possesses: (1) an approximately equi-dimentional P1 blade element, (2) an accurate upper profile with denticle height descending in both directions, (3) a denticulated posterior edge (lower denticles posterior of the highest denticle), and (4) a round basal cavity outline. Of the three proposed subspecies of the waageni species, both Nv. waageni waageni (Sweet, 1970) and Nv. w. eowaageni (Zhao and Orchard, 2005) are valid, and the former differs clearly from Nv. w. eowaageni in having (1) a slightly higher length/height ratio (holotype=1.30 : 1.23), (2) a thicker blade, sometimes with medial thickening, (3) fewer (broader) denticles per unit length, (4) generally recurved denticles, not straight and upright, (5) highest denticles closer to posterior, (6) common differentiation of a posterior cusp, and (7) more sinuous basal profile, with increased posterior upturning. A third subspecies illustrated as Nv. waageni n. subsp. A sensu Goudemand, 2014 is not conspecific with older individuals of Nv. w. eowaageni, and also cannot be assigned to the Nv. waageni group. Abundant new materials demonstrate a clear ontogenic process for Nv. w. eowaageni, indicating that Nv. w. eowaageni occurring in the Induan−Olenekian boundary (IOB) succession is rather stable. Small, earlier individuals (i.e., those from Bed 225 in Jianshi) are referred to as Nv. w. eowaageni Morphotype A, and are thought to have likely evolved from Ns. dieneri Morphotype 3, and to be the precursor of mature elements of Nv. w. eowaageni. The first appearance datum of Nv. w. eowaageni therefore is an ideal mark defining the IOB.

Final Results and Recommendations of the Last 10 Years IGCP 572 and 630 Field Workshops in South Turkey, Oman, India (Kashmir) and Armenia

Being involved in the organization of IGCP 572 field workshops in Turkey (2009), in Oman (2010), as in the following IGCP 630 field workshops in Kashmir (India, 2014) and in Armenia (2017), I co-wrote for each of them detailed guidebooks and extended reports that can be found and downloaded from ResearchGate website. This paper summarizes the final results obtained by IGCP 572 and 630 members from these four important field workshop sites in the past 10 years, and also attempts to make recommendations for future studies based on these unique localities surrounding the Tethys Ocean. The first field workshop of IGCP 572 was organized in South Turkey in September, 2009, with the logistical support of Dr. Erdal Kosun from the Antalya University. Following the South Turkey field workshop, eight important papers have been published and concerned the well-preserved Permian-Triassic boundary (PTB) microbialites and their ecosystems (including ostracodes, brachiopods, and many of other clades). The 3rd IGCP 572 annual field workshop was held during February, 2010 in the Sultanate of Oman, with Dr. Michaela Bernecker and the deep support from the GuTech University in Muscat. More than 15 papers have derived from the P-Tr successions that IGCP 572 members have investigated during this workshop, including the first study on oceanic acidification based on Boron isotopes. New paleontological studies are still on progress, and concern the Smithian ammonoids, Lower Triassic shark teeth and dental remains as well as basal Triassic conodonts, crinoids and ammonoids. The 1st IGCP 630 annual field workshop was held during November, 2014 in Srinagar, Kashmir, and North India, with the helpful assistance of Prof. Ghulam Bhat from Jammu University. This meeting renewed studies on the classic Guryul Ravine and adjacent P-Tr boundary sections in that region, with new geochemical works on carbon isotopes and pyrite framboids as well as a detailed Induan conodont taxonomy and zonation. Other new paleontological works concern the palynology of the Guryul Ravine Section as some well-preserved organic eukariotic protist (thecamoebians) that cross without damage the PTB. Lilit Sahakyan, Aymon Baud, and Zhong-Qiang Chen organized the 5th IGCP 630 annual conference and field workshop in Armenia on October 8–14, 2017. Several PTB and Lower Triassic sections have been systematically sampled for biogeochemical and geobiological studies. These Armenian sections provide unique paleoenvironmental settings that have the longest record, from Griesbachian to Dienerian, of microbial proliferation following the P-Tr mass extinction in the world. The basal Triassic giant sponge-microbial build-ups are encouraging more comprehensive studies on metazoan-microbial reef developments after the greatest extinction event.

Earliest Triassic Conodonts of Gua Panjang, Merapoh, Pahang and their Bearing towards Permian-Triassic Mass Extinction in Malaysia

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.

Heterogeneity of conodont faunas in the Cache Creek Terrane, Canada; significance for tectonic reconstructions of the North American Cordillera

The oceanic Cache Creek Terrane has long been interpreted to be exotic relative to the neighbouring Stikine and Quesnel terranes, on the basis of its unusual fossil faunas. Current tectonic models for the amalgamation of these three terranes have to account for the position of the exotic Cache Creek Terrane between two volcanic island arc terranes, and competing models invoke either terrane entrapment or strike-slip motion to explain this configuration. Although previous paleobiogeographic studies have attempted to assess the degree of faunal variability among terranes of the North American Cordillera, none have yet measured the amount of internal faunal heterogeneity and considered the effect that this may have on tectonic reconstructions. The use of multivariate statistics demonstrates that the Late Paleozoic to Triassic conodont faunas from the Cache Creek Terrane show distinct heterogeneity. The degree of heterogeneity among faunas from different regions of the terrane varies with time, and does not correlate with temporal changes in depositional environment, conodont ecology, or species endemism. Instead, it is proposed that the Cache Creek Terrane may consist of a number of sub-terranes which moved independently of each other prior to the final accretion of the Intermontane terranes. Periods of low faunal heterogeneity may correspond to times when the sub-terranes were close together, whereas periods of high heterogeneity may indicate that the sub-terranes had moved further apart. This interpretation requires that tectonic models for the formation of this part of the Cordillera emphasise lateral movement both within and between terranes prior to accretion.

Integrated Upper Triassic Conodont and Radiolarian Biostratigraphies of the Panthalassa Ocean

The Late Triassic conodont biostratigraphy of two pelagic chert sections (sections N and Q) in the Inuyama area, central Japan, was investigated to calibrate the Triassic radiolarian zonation proposed by Sugiyama in 1997 with the conodont zones and the standard Triassic timescale. Based on the stratigraphic distributions of marker species, six conodont zones were defined: the Paragondolella? tadpole interval Zone, the Quadralella tuvalica interval Zone, the Epigondolella quadrata interval Zone, the E. triangularis interval Zone, the Mockina postera interval Zone, and the M. bidentata Zone. These conodont zones are comparable to the standard Carnian and Norian conodont zones of North America and the Tethys. The Carnian-Norian boundary in the sections studied is tentatively placed between the last occurrence of a Carnian species (Q. tuvalica) and the first occurrences of Norian species (E. quadrata and E. spatulata). The intercalibrated conodont—radiolarian biostratigraphy from the sections we studied accurately calibrates the radiolarian zones in Japan with standard chronostratigraphic stages and substages.