Triassic Conodonts Research Articles

Early Triassic conodonts from the Liangshan area, Hanzhong, Shaanxi, South China

Early Triassic conodonts from the Liangshan area, Hanzhong, Shaanxi, South China

Morphological innovation after mass extinction events in Permian and Early Triassic conodonts based on Polygnathacea

Taxonomic diversity of marine animals decreased markedly during the end-Guadalupian and end-Permian mass extinctions, but conodonts were largely unaffected by these two major events. This conclusion is largely based on potentially problematic conodont taxonomy, but quantitative analyses of conodont morphology have received little attention, despite offering key insights into macroevolutionary dynamics. Polygnathacea conodonts seemingly evolved fast and had high morphological diversity, and are therefore ideal for exploring morphospace trends and disparity related to environmental change in conodonts. Here we compiled discrete character-taxon matrices to first refine phylogenetic interpretations and then explore morphological disparity in four related conodont families, the Anchignathodontidae, Sweetognathidae, Idiognathodontidae and Vjalovognathidae, from the Permian to Early Triassic. Our findings reveal morphological innovation and exploration of new morphospace after the end-Guadalupian mass extinction and end-Permian mass extinction. We also show that the smaller end-Guadalupian extinction event was more impactful, resulting in greater losses of morphological disparity and taxonomic diversity, than the larger end-Permian extinction event. Overall, our study reveals morphological disparity trends related to temporal evolutionary dynamics for conodonts during the geologically and environmentally turbulent Permian and Early Triassic. We show that conodonts are affected by extinction events during this interval in terms of morphological diversity, rather than simply taxonomic diversity.

Lower to Middle Triassic conodont biostratigraphy and carbonate carbon isotope chemostratigraphy of the Zuodeng area, Guangxi, South China, and its relevance for stratigraphic correlation from the Induan to the Anisian

The Nanpanjiang Basin in South China is a vital area for studying the Early Triassic marine ecosystem recovery in the aftermath of the end-Permian mass extinction (EPME). The Zuodeng sections (A, B, and C) are located on the Debao platform, one of the isolated shallow-water platforms within the Nanpanjiang Basin. This area preserves a relatively complete conodont succession from the Lower Triassic to the lower Middle Triassic. Here, a total of 12 conodont zones and 4 subzones are established, namely, the Hindeodus postparvus Zone, the Hindeodus sosioensis Zone, the Neoclarkina krystyni Zone, the Neoclarkina discreta Zone, the Neospathodus dieneri Zone (including the Neospathodus dieneri M1 and Neospathodus dieneri M3 subzones), the Neospathodus cristagalli Zone, the Neospathodus pakistanensis Zone, the Novispathodus waageni eowaageni Subzone, the Novispathodus waageni waageni Subzone, the Neospathodus yangtzeensis-Novispathodus shani Zone, the Novispathodus pingdingshanensis Zone, the Triassospathodus homeri Zone, the Neospathodus triangularis Zone and the Chiosella timorensis Zone.The Permian-Triassic boundary is placed at the base of Bed 48 in the Zuodeng A section, coinciding with the base of the widespread microbialite beds and the carbon isotope excursion. The Induan-Olenekian boundary is placed at the bases of Bed 86 and Bed 21 in the Zuodeng A and Zuodeng B sections, respectively, where Nv. ex gr. waageni occurs at or slightly below the peak of the positive δ13Ccarb excursion. The Smithian-Spathian boundary is recognized at the bases of Bed 92 and Bed 33 in the Zuodeng A and Zuodeng B sections, respectively, based on the first occurrence (FO) of Nv. pingdingshanensis near the middle point of the positive δ13Ccarb excursion. The Olenekian-Anisian boundary is drawn at the top of Bed 5 in the Zuodeng C section based on the FO of Ch. timorensis. The conodont zones recognized in the Zuodeng area correlate well with sections in South China and elsewhere worldwide. The Ns. yangtzeensis-Nv. shani Zone is newly established, and the recognition of this zone in several sections significantly improves the accuracy of stratigraphic subdivision and correlation of the Smithian. The conodont zones in the Zuodeng area thus provide a high-precision time scale for future studies on marine ecosystem recovery in the aftermath of the EPME and environmental events during the Early Triassic.

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.

Upper Triassic (middle Norian) conodont biostratigraphy succession from Qamdo, eastern Tibet

The Late Triassic is a critical period that witnessed major biological and environmental events. The geographic range and taxonomic diversity of conodonts were significantly changed during the Late Triassic, with the geographic range contracting prior to complete extinction of the group near the end of the Triassic. In the present study, we recognize for the first time a continuous middle Norian (Upper Triassic) conodont succession from the Qamdo (Changdu) area, eastern Tibet (Xizang), which was part of the North Qiangtang and Qamdo-Simao Block (NQ-QSB) located in the northeastern Tethys Ocean during the Late Triassic. Four conodont zones are established from the middle Norian (Alaunian) of the Chaiwei section in Qamdo, and in ascending order these are: the Epigondolella spiculata Zone, the Orchardella elongata Zone, the Mockina postera Zone, and the E. serrulata Zone; the neighboring Tuoba section also records these four zones, in addition to the upper lower Norian (upper Lacian) Ancyrogondolella uniformis Zone. All of these zones (except for the M. postera Zone) have been recognized for the first time in eastern Tibet. The Lacian-Alaunian boundary is tentatively placed at the level of sample CW-3 at the Chaiwei section and at the level of sample TBL-36 at the Tuoba section by the first occurrence (FO) of E. spiculata in each section. The position of the Alaunian-Sevatian boundary (ASB) is uncertain since the conodont assemblage from the top of the Bolila Formation at the study sections lacks age-diagnostic elements. The conodonts recovered from the Qamdo area have not only dated the Bolila Formation but also refined the conodont biostratigraphic zonation of the Alaunian in the study area. This allows improved correlation between the faunas of Qamdo and their counterparts elsewhere in Tibet and Europe, although the conodont zonations from these regions display lower precision than those established from North America. The Alaunian conodont faunas at Chaiwei and Tuoba appear to be dominated by juvenile specimens; this often appears to be the case in the Alaunian of the Tethyan Realm, but seems not occur in North America. This may suggest that the conodonts living in these two realms may have inhabited different ecological environments. The faunal turnover around the Lacian-Alaunian transition, with the evolution of Epigondolella, Orchardella, and Mockina from Ancyrogondolella, can be recognized in both study sections, although it is more remarkable in the Tuoba section. Although the lack of previous detailed studies of Norian conodont biostratigraphy from Tibet hampers correlation in this region and beyond, this study demonstrates the possibility of establishing high-resolution conodont biostratigraphic successions from Tibet in the future, since the conodont faunas recognized from Tibet and adjacent areas (e.g., Baoshan) suggest that relatively complete Norian strata exist in these regions. Overall, this study also provides new data to improve our understanding of conodont evolution during the Alaunian, and is significant in providing palaeontological data for studying the palaeogeographic evolution of eastern Tethyan ocean basins in the Late Triassic.

The utility of the Upper Triassic conodont Primatella in Tethyan-Panthalassan correlation around the Carnian-Norian boundary

The Upper Triassic conodont genus Primatella is important for recognizing the Carnian-Norian stage boundary in Panthalassan and Tethyan domains. Originally based on Canadian material from Black Bear Ridge in the Western Canada Sedimentary Basin, two key species are highlighted, and their occurrence is documented in the allochthonous Wrangellia and Alexander terranes in the North American Cordillera; in the Great Basin in Nevada, western United States; at Pizzo Mondello, Sicily, in western Tethys; and in Timor-Leste on the southeastern margin of the Meso-Tethys Ocean (northeastern Gondwana). The correlation potential of Primatella species is compromised by a differing nomenclature employed in Tethyan regions of Europe where Primatella species have been assigned to other genera, namely, Ancyrogondolella (formerly Epigondolella), Carnepigondolella, and Metapolygnathus. This has obscured phyletic relationships and impacted the stratigraphic utility of two demonstrably cosmopolitan species, P. asymmetrica and P. bifida. These species are shown to occur widely in a variety of paleoenvironments and have a restricted stratigraphic range around the CNB for which they can be adopted as useful indices.

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.

Comparisons of age estimates from Strontium-isotope values versus other Chronostratigraphy methods

Strontium-isotope stratigraphy enables estimates of numerical dates for marine carbonate-bearing sediments by comparing their 87Sr/86Sr ratio to a reference curve of 87Sr/86Sr variations of global seawater through geologic time. That seawater reference curve is a published statistical LOWESS fit to a very large dataset (ca. 14,000) of 87Sr/86Sr measurements of carbonate fossils from known biozones which is converted to numerical ages using published timescales. In this study, we compute the numerical dates projected by this method for suites 87Sr/86Sr ratios from seven stratigraphic sections ranging from Ordovician through Oligocene. The strontium-isotope stratigraphy from the Dawangou section in Tarim Basin of NW China that hosts the Auxiliary GSSP for the base of the Late Ordovician is a new dataset; and the others are published datasets. These 87Sr/86Sr-derived dates are compared to those estimated for the same horizons in these sections by other chronostratigraphic methods, including cyclostratigraphy calibrated to radioisotopic dates and standard biochronostratigraphy. Except for a published study of Lower Triassic strata from Chaohu section in Anhui, China and Middle Devonian strata Jebel Mech Lrdane section of Morocco, all the 87Sr/86Sr-derived dates are within the estimated uncertainties of the dates from the other chronostratigraphic methods, thereby validating the usefulness of strontium-isotope stratigraphy as one tool for obtaining the ages of marine carbonate-bearing deposits. However, the datasets from all three Paleozoic sections (two Ordovician, one Devonian) did display a noticeable offset bias toward older ages, which may be partly an artifact of inadequate adjustment of the LOWESS reference curve to current age models for the biozones. The 87Sr/86Sr-derived dates from Chaohu section of Early Triassic conodont zones were unacceptably systematically younger by ca. 1.45 Myr; thereby indicating higher-than-expected 87Sr/86Sr values, which may have been partially the result of a combination of a semi-restricted basin that was slightly diluted by 87Sr-enriched fluvial waters from the chemical weathering of adjacent landmasses and of the laser ablation (LA-ICP-MS) analytical method applied to those samples that seems to yield higher 87Sr/86Sr ratios than the solution-mode ICP-MS method for 87Sr/86Sr measurements. In summary, with rare exceptions, the method of strontium-isotope stratigraphy and the statistical 87Sr/86Sr seawater curve is an important method to obtain semi-precise numerical dates from marine carbonate sediments.

A unique early Triassic (Spathian) conodont community from the Nanzhang‐Yuan'an Fauna, Hubei Province, South China

The largely stagnant marine ecosystem following the Permian–Triassic mass extinction (PTME) was superseded by the appearance of marine reptiles. One of the most abundant Early Triassic (Spathian) marine reptile faunas occurs in the Nanzhang‐Yuan'an area of Hubei Province, South China, and provides remarkable information for understanding biotic recovery after the PTME. Situated on the north edge of the Middle Yangtze Platform in South China, the well‐exposed Zhangjiawan stratigraphic succession in Yuan'an County represents one of the most productive sections, yielding abundant marine reptiles. Intensive sampling of this section reveals a unique conodont community both before and during the emergence of the Nanzhang‐Yuan'an Fauna (NYF). Occurrences of Neostrachanognathus tahoensis below the NYF and deposition of ʻGreen Bean Rock (GBR)ʼ above the NYF restricted this fauna to the latest Early Triassic. Except for the coniform Neostrachanognathus, this conodont community consists of abundant Ellisoniidae characterized by ramiform P1 elements. Foraminifers and fish found together with the conodont elements form other low‐level parts of the local food web. Other temporally coincident sections nearby, for example, the Yanduhe section of western Hubei Province, yield only rare conodonts. Hence, the unique conodont community from the Zhangjiawan section suggests that the Nanzhang‐Yuan'an area might be a “refuge area” for the Early Triassic marine ecosystem, or at least for the marine reptiles and the conodont communities. Although the direct connection between conodonts and marine reptiles is still uncertain, low‐level consumers—conodont animals‐played important roles in the food webs of NYF. The collision of the South China and North China blocks removed this “refuge area” and witnessed the disappearance of endemic Hupeisuchians.

Growth allometry and dental topography in Upper Triassic conodonts support trophic differentiation and molar-like element function

AbstractConodont elements have high rates of morphological evolution, but the drivers of this disparity are debated. Positive allometric relationships between dimensions of food-processing surfaces and entire P1 elements have been used to argue that these elements performed mechanical digestion. If involved in food processing, the surface of the element should grow at a rate proportional to the increase in energy requirements of the animal. This inference of function relies on the assumption that the energy requirements of the animal grew faster (≅ mass0.75) than the tooth area (≅ mass0.67). We reevaluate this assumption based on metabolic rates across animals and calculate the allometry in platform-bearing P1 elements of Late Triassic co-occurring taxa, Metapolygnathus communisti and Epigondolella rigoi, using 3D models of ontogenetic series. Positive allometry is found in platform and element dimensions in both species, supporting a grasping-tooth hypothesis, based on the assumption that metabolic rate in conodonts scaled with body mass similarly to that in fish and ectotherms. We also calculate the curvature of the P1 platform surface using the Dirichlet normal energy (DNE) as a proxy for diet. DNE values increase with body mass, supporting the assumption that conodont metabolic rates increased faster than mass0.67. We finally find that adults in both taxa differ in their food bases, which supports trophic diversification as an important driver of the remarkable disparity of conodont elements.

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.

Occurrence of Early Carboniferous Radiolarians and Middle Triassic Conodonts from Ban Rai, Southwestern Uthai Thani, Central Thailand and Its Geological Significance

A bedded chert succession, intercalated with layers of coarse-grained sandstone and chert conglomerate, and a limestone block with a long axis of about 10 m are distributed in the Ban Rai area, southwestern Uthai Thani, central Thailand. The chert yielded early Carboniferous (Tournaisian to Visean) radiolarians composed of 10 species of five genera; the limestone yielded Middle Triassic (early Anisian) conodonts comprising five species (P1 element). The lower Carboniferous chert was presumably deposited on the upper continental rise of the Sibumasu Terrane in the Paleotethys Ocean, based on radiolarian faunal characteristics. The Middle Triassic limestone was probably deposited on the continental shelf of the eastern margin of the Sibumasu Terrane, judging from the inclusion of silt-sized quartz grains. Because the blocks of the lower Carboniferous chert and Middle Triassic limestone are currently located in a narrow area, these blocks are inferred to have been mixed with each other by submarine sliding after at least the Middle Triassic at the eastern margin of the Sibumasu Terrane.

Integrated conodont biostratigraphy and δ13Ccarb records from end Permian to Early Triassic at Yiwagou Section, Gansu Province, northwestern China and their implications

The South Qinling Belt is a key area for understanding the collisional history of the South China and North China blocks during the Lopingian (late Permian) and Triassic. This paper establishes the first integrated timescale based on conodont biostratigraphy and δ13Ccarb records from a continuous end Permian to the end-Early Triassic succession at Yiwagou, South Qinling Platform (SQP). Ten Early Triassic conodont zones are established. They are, in ascending order, Hindeodus parvus, H. postparvus, Neospathodus dieneri, Eurygnathodus costatus and E. hamadai, Novispathodus waageni-Scythogondolella mosheri, Pachycladina-Parachirognathus assemblage, Triassospathodus hungaricus, Ns. robustispinus and T. clinatus zones. Our record of δ13Ccarb fluctuations shows close correspondence to known Early Triassic carbon isotope fluctuations and, in combination with the conodont data, helps achieve a high-resolution age model for the region. The use of E. costatus as a good auxiliary marker for the Induan-Olenekian boundary (IOB), within palaeolatitudes of 40°N-40°S, is supported but it can not replace the use of Nv. waageni, because the former is absent in higher-latitude and cooler regions. The conodont faunas from the Palaeo-Tethyan Yiwagou section closely resemble those from the Northern Yangtze Platform (NYP), but they differ somewhat from the contemporaneous Nanpanjiang Basin at species level. Thus, the Qinling Sea was likely well connected with the NYP in the Early Triassic, but was more isolated from the Nanpanjiang Basin. The remarkable reappearance of Hindeodus fauna around the IOB at Yiwagou implies that the shallow-water Qinling Sea was a refuge area for this genus long after its disappearance elsewhere.

Phylogenetic classification and evolution of Early Triassic conodonts

Conodonts are some of the most important biostratigraphic index fossils in the Paleozoic and Triassic because of their rapid evolution and extensive distribution. Here we present a cladistic analysis of Early Triassic conodonts to reexamine the systematic classification and evolutionary relationships of the three related families Anchignathodontidae, Ellisonidae, and Gondolellidae. The tree consists of 38 Early Triassic conodont species with multielement apparatus documented, based on parsimony analysis of 73 discrete morphological characters including 40 P 1 element characters, 4 P 2 element characters, 27 S element characters and 2 M element characters. Based on the phylogenetic time tree, a series of evolutionary lineages are supported: Parafurnishius xuanhanensis – Furnishius triserratus – Platyvillosus regularis ; Scythogondolella mosheri – Scythogondolella milleri ; Discretella – Conservatella – Paullella meeki ; Triassospathodus homeri – Chiosella ; and Triassospathodus symmetricus – Triassospathodus chioensis . Reassignment of Ellisonia agordina to be Hadrodontina agordina is supported while Neospathodus planus should be resigned to the genus Triassospathodus . Meanwhile, Parafurnishius and Furnishius may belong to Gondolellidae rather than Ellisonidae or Ellisonidae may be a polyphyletic group rather than a monophyletic group. The cladogram suggests that Hindeodus , Hadrodontina and Pachycladina are monophyletic, whilst Novispathodus and Triassospathodus are paraphyletic and polyphyletic, respectively. In addition, a P 1 element with a round basal cavity is an important trait to distinguish Novispathodus from Triassospathodus . The cladogram and revised classification provide a robust phylogenetic foundation for further investigations on systematic classification and evolutionary rates of conodonts during the Early Triassic. • A multi-element cladistic tree of 38 conodont species is established. • The tree reexamines the classification and evolution of these 38 species. • Hindeodus , Hadrodontina and Pachycladina are monophyletic. • Novispathodus are paraphyletic and Triassospathodus are polyphyletic. • Neospathodus planus should be resigned to the genus Triassospathodus .

Lower Triassic conodont biostratigraphy of the Guryul Ravine section, Kashmir

The Guryul Ravine section in Kashmir, northern India is an important reference section for global Lower Triassic stratigraphy. Once a candidate Global Stratotype Section and Point (GSSP) for the Permian-Triassic Boundary (PTB), the section has attracted intense attention for the PTB beds, but few studies have concerned the entire Lower Triassic stratigraphy. As one of the most continuous marine Lower Triassic successions on the northern margins of Gondwana, the Guryul Ravine section provides an important conodont biostratigraphic yardstick for worldwide correlations. This study presents recent results of the Lower Triassic conodont zonation from the Guryul Ravine section. A total of 6500 elements including 1600 P1 elements were recovered. Ten conodont zones were recognized from the Griesbachian to Spathian: Hindeodus parvus, Isarcicella staeschei, Clarkina planata, Neoclarkina krystyni, Neospathodus dieneri, Ns. pakistanensis, Novispathodus waageni, Scythogondolella mosheri, Nv. pingdingshanensis, and Nv. abruptus – Nv. brevissimus zones. The PTB is placed within Bed 52 in Unit E2, 80 cm above the base of Unit E2, based on the first occurrence (FO) of H. parvus. The Induan–Olenekian boundary (IOB) is tentatively placed at the base of Member G according to the positive maximum δ13Ccarb values, but it could be slightly higher based on conodonts. The Smithian-Spathian boundary (SSB) is drawn at the top of Member H based on the FO of Nv. pingdingshanensis and the carbon mdpt(N3-P3). Several conodont taxa are newly recognized near the top of the study section where the conodont fauna is dominated by segminiplanate elements of the Neogondolellinae. Many of these age-diagnostic species have been identified in other sections around the world, and their occurrence in Guryul Ravine supports their potential for worldwide correlation. The conodont sequence erected from the study section corresponds well to those of South China (e.g. Meishan) and elsewhere worldwide. The newly established conodont zonation from Kashmir provides a high precision time-frame to consider biotic evolution and environmental change during the Early Triassic, a crucial period of Earth history.

A new study of Olenekian–Anisian boundary conodont biostratigraphy of the Tulong section in Himalaya Terrane, southern Tibet

The Himalaya Terrane of southern Tibet exposes successive shallow-marine carbonate deposits from the Lower to Upper Triassic, and is a key region for studying the Triassic conodont biostratigraphy at the northern margin of the Indian Plate. On the basis of newly collected samples from the Kangshare and Laibuxi formations at the Tulong section, 11 conodont species of 7 genera were identified, and four conodont zones were established, namely, the Novispathodus abruptus Zone (lower Spathian, first reported in Tibet), the Columbitella jubata Zone (middle Spathian), the Triassospathodus symmetricus Zone (upper Spathian), and the Chiosella timorensis Zone (lowermost Anisian) in ascending order. The first occurrence (FO) of Chiosella timorensis indicates the Olenekian–Anisian boundary (OAB) at Bed 25, upper part of the Kangshare Formation. The regional and global correlation of these conodont zones is synthesized.

A review of the Late Triassic conodont conundrum: survival beyond biotic perturbations

A review of the Late Triassic conodont conundrum: survival beyond biotic perturbations

Newly discovered Wuchiapingian to Olenekian conodonts from the Longgar area, southern Lhasa Terrane and their palaeobiogeographical implications

Biostratigraphical, geochemical and palaeomagnetic studies have demonstrated that the Lhasa Terrane occupied a low-latitude southern hemisphere region during Late Permian to Early Triassic time. However, the palaeogeographical relationship of the South Qiangtang and the Lhasa terranes remains a topic of debate. The principal dispute focusses are on whether the Bangong-Nujiang Suture Zone (BNSZ) separating the terranes was an ocean during the Late Permian to Early Triassic. Resolution of this problem requires the recognition and investigation of Permian - Triassic boundary (PTB) deposits and fossils of the Lhasa Terrane, especially proximal to the E-W trending Longgar-Gongbujiangda Fault, a region that has heretofore been considered devoid of these deposits. Our investigation of the Longgar area reveals that carbonate deposits correlated with the Middle Permian Xiala Formation are similar to PTB rocks described from elsewhere. We recovered conodont faunas spanning the Wuchiapingian and Changhsingian stages of the Permian and the Early Triassic Olenekian stage. Our results demonstrate that the studied carbonate succession ranges from the Upper Permian to the Upper Triassic (perhaps to the Lower Jurassic). The documented conodont succession demonstrates that PTB strata accumulated in the Longgar area. Thus, Late Permian and Early Triassic conodonts described from the Lhasa Terrane suggest a connection with the South Qiangtang Terrane. The BNSZ during this period of time was part of a carbonate platform that connected the Lhasa Terrane and the South Qiangtang Terrane.

Middle Triassic (Anisian) Conodont Biostratigraphy at the Shaiwa Section, Guizhou, South China

Middle Triassic (Anisian) Conodont Biostratigraphy at the Shaiwa Section, Guizhou, South China

Late Triassic (Norian) Conodont Apparatuses Revealed by Conodont Clusters from Yunnan Province, Southwestern China

Almost all aspects of conodont research rely on a sound taxonomy based on comparative analysis. This is founded on hypotheses of homology which ultimately rest on knowledge of the location of elements in the apparatus. Natural assemblages—fossils that preserve the articulated remains of the conodont skeletal apparatus—provide our only direct evidence for element location, but very few are known from the Late Triassic. Here we describe fused clusters (natural assemblages) from the late Norian limestone beds of the Nanshuba Formation in Baoshan, Yunnan Province, southwestern China. Recurrent arrangements and juxtaposition of S and M elements in multiple clusters reveal the composition of the apparatus of Mockina and, probably, Parvigondolella. They indicate that these taxa had a standard 15 elements ozarkodinid apparatus, and provide new insights into the morphology of the elements occupying the P2, M and S locations of the apparatus. The apparatus comprised a single alate (hibbardelliform) S0 element, paired breviform digyrate (grodelliform) S1 and (enantiognathiform) S2 elements, paired bipennate (hindeodelliform) S3 and S4 elements, paired breviform digyrate (cypridodellifrom) M elements, paired, modified-angulate P2 elements (with reduced or lacking ‘posterior’ process) and segminiplanate (mockiniform and parvigondolelliform) P1 elements. Our results will allow testing of the hypothesis that Mockina, Parvigondolella and Misikella—critical taxa in Late Triassic biostratigraphy—are closely related and possessed morphologically similar elements in homologous locations.