Comment on “Quantitative biochronology of the Permian–Triassic boundary in South China based on conodont unitary associations” by Brosse et al. (2016)

Recently, Brosse et al. (2016) have proposed the use of conodont Unitary Associations Zones (UAZs) to substantially modify the biostratigraphy of the Permian–Triassic transition and to redefine the Permian–Triassic boundary (PTB). However, in our opinion, the UAZ analysis presented by Brosse et al. (2016) is based on unreliable taxonomic data sets with unjustified taxonomic re-assessments. No evidence shows that the UAZ approach improves the biozone biostratigraphy currently used to date the PTB

Dating the onset and nature of the Middle Permian Emeishan large igneous province eruptions in SW China using conodont biostratigraphy and its bearing on mantle plume uplift models

The Middle Permian Emeishan large igneous province of SW China has provided the quintessential example of the phenomenon of kilometre-scale pre-eruption domal uplift associated with mantle plume impingement on the base of the lithosphere. One key line of evidence is an interpreted zone of truncation of the platform carbonates belonging to the Maokou Formation that underlies the volcanic pile. Here we test this interpretation by conodont age dating the uppermost beds of the Maokou Formation in sections from Yunnan, Sichuan, Guizhou and Guangxi provinces, which span locations from the inner part of the igneous province to several hundred kilometres beyond its margins. The results show that eruptions began in the Jinogondolella altudaensis Zone ( 263 Ma) of the Middle Capitanian Stage and greatly increased in extent and volume in the J. xuanhanensis Zone ( 262 Ma). Pre-eruption uplift was muted, and most locations within the terrain and at many locations beyond its margins witnessed platform collapse (not uplift) with deep-water facies (radiolarian cherts, submarine fans) developing in the J. altudaensis Zone. The clearest evidence for an emergence surface occurs around the margins of the province in the J. xuanhanensis Zone. This is after the initial onset of eruptions and marks either a eustatic sequence boundary or a brief pulse of tectonic uplift contemporaneous with volcanism. As with recent studies on the basal volcanic successions of the Emeishan LIP, kilometre-scale plume-related domal uplift prior to Emeishan eruptions is not supported by these data; rather a more complex interaction between plume and lithosphere with minor localized uplift and subsidence is inferred

Smithian platform-bearing gondolellid conodonts from Yiwagou Section, northwestern China and implications for their geographic distribution in the Early Triassic

Abundant platform-bearing gondolellid conodonts, including Scythogondolella mosheri (Kozur and Mostler), Sc. phryna Orchard and Zonneveld, and Sc. cf. milleri (Müller), have been discovered from the Yiwagou Section of Tewo, together with Novispathodus waageni waageni (Sweet) and Nv. w. eowaageni Zhao and Orchard. This is the first report of Smithian platform-bearing gondolellids from the Paleo-Tethys region. In addition, Eurygnathodus costatus Staesche, E. hamadai(Koike), Parafurnishius xuanhanensis Yang et al., and the genera Pachycladina Staesche, Parachirognathus Clark, and Hadrodontina Staesche have also been recovered from Dienerian to Smithian strata at Yiwagou Section. Three conodont zones are established, in ascending order: Eurygnathodus costatus-E. hamadai Assemblage Zone, Novispathodus waageni-Scythogondolella mosheri Assemblage Zone, and the Pachycladina-Parachirognathus Assemblage Zone. The platform-bearing gondolellids were globally distributed just after the end-Permian mass extinction, but the formerly abundant Clarkina Kozur disappeared in the late Griesbachian. Platform-bearing gondolellids dramatically decreased to a minimum of diversity and extent in the Dienerian before recovering in the Smithian. Scythogondolella Kozur, probably a thermophilic and eurythermic genus, lived in all latitudes at this time whereas other genera did not cope with Smithian high temperatures and so became restricted to the high-latitude regions. However, the maximum temperature in the late Smithian likely caused the extinction of almost all platform-bearing gondolellids. Finally, the group returned to equatorial regions and achieved global distribution again in the cooler conditions of the late Spathian. We conclude that temperature (and to a lesser extent oxygen levels) exerted a strong control on the geographical distribution and evolution of platform-bearing gondolellids in the Early Triassic

A review of the Late Permian – Early Triassic conodont record and its significance for the end-Permian mass extinction

As a marine microfossil with a long-lasting fossil record stretching from the Cambrian to the Triassic, the tiny conodont plays an important role for the study of the end-Permian mass extinction. In the past few decades, numerous studies on Permian-Triassic conodonts have been published. This paper summarizes the progress made on high-resolution conodont biostratigraphy, timing of the mass extinction across the Permian-Triassic Boundary, conodont apparatus and phylogeny, conodont size variation, conodont oxygen isotope as well as other isotopes and chemical elements. Finally, future perspectives are also discussed

Data from: Testing hypotheses of element loss and instability in the apparatus composition of complex conodonts: articulated skeletons of Hindeodus

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

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