Arnaud Brayard - Academia.edu (original) (raw)

Papers by Arnaud Brayard

Genus Porpoceras Buckman, 1911 TYPE SPECIES. — Ammonites &l... more Genus Porpoceras Buckman, 1911 TYPE SPECIES. — Ammonites vortex Simpson, 1855 by monotypy.

Rivista Italiana Di Paleontologia E Stratigrafia, 2006

Early Triassic (Griesbachian to Spathian) ostracod faunas are here first discovered and described... more Early Triassic (Griesbachian to Spathian) ostracod faunas are here first discovered and described form the Guangxi Province, South China. Thirty-seven species belonging to fourteen genera are recognized. Seven species are new: Bairdia fengshanensis n.sp., Bairdia wailiensis n.sp., Liuzhinia guangxiensis n.sp., Ptychobairdia luciaae n.sp., Ptychobairdia aldaae n.sp., Paracypris jinyaensis n.sp. and Paracypris gaetanii n.sp. The Griesbachian assemblage from the basal microbial limestone is well diversified and does not suggest any abnormal palaeoenvironmental conditions in terms of salinity, temperature or oxygen content. Particularly, the ostracods are typical of well oxygenated water and do not reflect any anoxia. Dienerian and Smithian ostracods are evidenced for the first time and the assemblages suggest less favourable palaeoenviromental conditions. Diversity and abundance of ostracod assemblages recovered from the Spathian on. The main taxonomic turnover among ostracod assemblag...

1 Palaontologisches Institut der Universitat Zurich, Karl Schmid-Strasse 4, 8006 Zurich, Switzerl... more 1 Palaontologisches Institut der Universitat Zurich, Karl Schmid-Strasse 4, 8006 Zurich, Switzerland, email: galfetti@pim.uzh.ch, hugo.FR.bucher@pim.uzh.ch, bruehwiler@pim.uzh.ch, goudemand@pim.uzh.ch, peter.hochuli@erdw.ethz.ch; 2 Department of Mineralogy, University of Geneva, rue des Maraichers 13, CH-1205 Geneva, Switzerland, email: maria.ovtcharova@terre.unige.ch, urs.schaltegger@terre.unige.ch; 3 UMR 5125 PEPS CNRS, Universite Lyon I, Campus de la Doua, 69622 Villeurbanne Cedex, France, email: arnaud.brayard@univ-lyon1.fr, Fabrice.Cordey@univ-lyon1.fr; 4 Department of Earth Science, ETH, Sonneggstrasse 5, 8006 Zurich, Switzerland, email: helmut.weissert@erdw.ethz.ch; 5 Guangxi Bureau of Geology and Mineral Resources, Jiangzheng Road 1, 530023 Nanning, China

The end-Permian mass extinction is the biggest known crisis in life history and wiped out more th... more The end-Permian mass extinction is the biggest known crisis in life history and wiped out more than 90% of all marine species. In its aftermath, the Early Triassic was a time of profound instabilities in the sedimentary, geochemical and climatic evolution. Full recovery of many marine, essentially benthic clades as well as pre-crisis level of marine ecosystem complexity was not reached until the Middle Triassic (e.g. reefal communities). On the contrary, at least some faunal groups such as ammonoids and conodonts recovered much faster than other marine clades. However, the evolution of Early Triassic ammonoids was not a smooth, nor a gradual process. It was characterized by the following main features: (i) a very low diversity in the Griesbachian (early Induan), (ii) a moderate diversity increase in the Dienerian (late Induan), (iii) an explosive radiation in the early Smithian (early Olenekian), (iv) a late Smithian extinction event followed by (v) a second explosive radiation in t...

Geobios, 2021

Abstract The late Smithian extinction represents a major event within the Early Triassic. This ev... more Abstract The late Smithian extinction represents a major event within the Early Triassic. This event generally corresponds to a succession of two, possibly three successively less diverse, cosmopolitan ammonoid assemblages, which when present, provide a robust biostratigraphic framework and precise correlations at different spatial scales. In the western USA basin, known occurrences of latest Smithian taxa are rare and until now, have only been documented from northeastern Nevada. Based on these restricted basinal occurrences, a regional zone representing the latest Smithian was postulated but not corroborated, as representative taxa had not yet been reported from outside Nevada. Here we document two new ammonoid assemblages from distant localities in northern Utah, overlying the late Smithian Anasibirites beds and characterized by the unambiguous co-occurrence of Xenoceltites subevolutus and Pseudosageceras augustum. The existence of a latest Smithian zone in the western USA basin is therefore validated, facilitating the identification of the Smithian/Spathian boundary and intra-basin correlation. This zone also correlates with the latest Smithian zone recognized from southern Tethyan basins. Additionally, these new data support other observed occurrences of Xenoceltites subevolutus throughout most of the late Smithian.

Scientific Reports, 2021

The mass extinction characterizing the Permian/Triassic boundary (PTB; ~ 252 Ma) corresponds to a... more The mass extinction characterizing the Permian/Triassic boundary (PTB; ~ 252 Ma) corresponds to a major faunal shift between the Palaeozoic and the Modern evolutionary fauna. The temporal, spatial, environmental, and ecological dynamics of the associated biotic recovery remain highly debated, partly due to the scarce, or poorly-known, Early Triassic fossil record. Recently, an exceptionally complex ecosystem dated from immediately after the Smithian/Spathian boundary (~ 3 myr after the PTB) was reported: the Paris Biota (Idaho, USA). However, the spatiotemporal representativeness of this unique assemblage remained questionable as it was hitherto only reported from a single site. Here we describe three new exceptionally diverse assemblages of the same age as the Paris Biota, and a fourth younger one. They are located in Idaho and Nevada, and are taxonomic subsets of the Paris Biota. We show that the latter covered a region-wide area and persisted at least partially throughout the Spa...

Global and Planetary Change, 2020

BMC Evolutionary Biology, 2019

Background Many pathologies that modify the shell geometry and ornamentation of ammonoids are kno... more Background Many pathologies that modify the shell geometry and ornamentation of ammonoids are known from the fossil record. Since they may reflect the developmental response of the organism to a perturbation (usually a sublethal injury), their study is essential for exploring the developmental mechanisms of these extinct animals. Ammonoid pathologies are also useful to assess the value of some morphological characters used in taxonomy, as well as to improve phylogenetic reconstructions and evolutionary scenarios. Results We report on the discovery of an enigmatic pathological middle Toarcian (Lower Jurassic) ammonoid specimen from southern France, characterized by a pronounced left-right asymmetry in both ornamentation and suture lines. For each side independently, the taxonomic interpretations of ornamentation and suture lines are congruent, suggesting a Hildoceras semipolitum species assignment for the left side and a Brodieia primaria species assignment for the right side. The fo...

Geobios, 2019

Abstract Intensive sampling of three earliest Spathian sites represented by the Lower Shale unit ... more Abstract Intensive sampling of three earliest Spathian sites represented by the Lower Shale unit and coeval beds within the Bear Lake vicinity and neighboring areas, southeastern Idaho, yielded several new ammonoid and nautiloid assemblages. These new occurrences overall indicate that the lower boundary of the Tirolites beds, classically used as a regional marker for the base of the early Spathian, and therefore the regional Smithian/Spathian boundary, must be shifted downward into the Lower Shale unit and coeval beds. Regarding ammonoids, one new genus (Caribouceras) and two new species (Caribouceras slugense and Albanites americanus) are described. In addition, the regional temporal distribution of Bajarunia, Tirolites, Columbites, and Coscaites is refined, based on a fourth sampled site containing a newly reported occurrence of the early Spathian Columbites fauna in coeval beds of the Middle Shale unit. As a complement to ammonoids, changes observed in nautiloid dominance are also shown to facilitate correlation with high-latitude basins such as Siberia during this short time interval, and they also highlight the major successive environmental fluctuations that took place during the late Smithian–early Spathian transition.

Geobios, 2019

Protomonaxonid sponges are a major group of Cambrian and Ordovician fossils in exceptionally pres... more Protomonaxonid sponges are a major group of Cambrian and Ordovician fossils in exceptionally preserved (especially Burgess Shale-type) faunas, but are rare thereafter. Rare examples of apparent surviving lineages are known from the late Palaeozoic and Mesozoic, but by this time more derived groups of sponges have generally displaced them in at least shallow-water (shelf depth) ecosystems. The early Spathian (Early Triassic) Paris Biota includes abundant material of a new leptomitid protomonaxonid, Pseudoleptomitus advenus Botting nov. gen., nov. sp., distinguished by having an unbundled longitudinal skeleton and very weak transverse component. This is the first post-Ordovician leptomitid known, and indicates long-term survival of the group in unknown environments. Its occurrence near storm wave base is similar to the preferred environment of earlier examples of the family, suggesting either ecological rarity or taphonomic reasons for their 200-million-year absence from later Palaeozoic rocks.

Genus Porpoceras Buckman, 1911 TYPE SPECIES. — Ammonites &l... more Genus Porpoceras Buckman, 1911 TYPE SPECIES. — Ammonites vortex Simpson, 1855 by monotypy.

Rivista Italiana Di Paleontologia E Stratigrafia, 2006

Geobios, 2021

Scientific Reports, 2021

Global and Planetary Change, 2020

BMC Evolutionary Biology, 2019

Geobios, 2019

As interest in the end Permian mass extinction event and the Triassic recovery has grown in recen... more As interest in the end Permian mass extinction event and the Triassic recovery has grown in recent decades, greater attention has necessarily been focussed on the time framework for this important interval. Intensive sampling of the lower portion of the Thaynes and Moenkopi Groups (Lower Triassic) in central and southern Utah (USA), has lead to the recognition of a new key regional Smithian ammonoid succession. The new biostratigraphic zonation is comprised of twelve subdivisions, resulting in a sequence with much higher resolution than the long-recognized Meekoceras gracilitatis and Anasibirites kingianus Zones, that can be correlated not only with other western USA sites, but also with major localities worldwide. Middle and late Smithian faunas contain many taxa with wide geographic distributions allowing long-distance correlation with faunal successions from other regions such as British Columbia, the Canadian Arctic, South China, Spiti and Oman. Combined with Dienerian data from Nevada, and Spathian data from Nevada, Idaho, California, and Utah, a refined biostratigraphic scheme for the Lower Triassic of the Western USA can be achieved.

Geological Society of …, Jan 1, 2009

The Pahvant Range lies near the junction of three major geological provinces in the western USA: ... more The Pahvant Range lies near the junction of three major geological provinces in the western USA: the Basin and Range, the Rocky Mountains, and the Colorado Plateau. The complex geological milieu of central Utah provides both challenges and opportunities. Among these is the ...