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Hugo Bucher - One of the best experts on this subject based on the ideXlab platform.
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Marine Early Triassic Actinopterygii from Elko County (Nevada, USA): implications for the Smithian equatorial vertebrate eclipse
Journal of Paleontology, 2017Co-Authors: Carlo Romano, James F. Jenks, Romain Jattiot, Kevin G. Bylund, Torsten M Scheyer, Hugo BucherAbstract:The Early Triassic vertebrate record from low paleolatitudes is spotty, which led to the notion of an ‘equatorial vertebrate eclipse’ during the Smithian. Here we present articulated ray-finned fishes (Actinopterygii), collected from the marine Lower Triassic Thaynes Group at three new localities in Elko County (Nevada, USA), which were deposited within the equatorial zone. From the Smithian of the Winecup Ranch, we describe two partial skulls of the predatory actinopterygian Birgeria (Birgeriidae), attributed to B. americana new species and Birgeria sp. Birgeria americana n. sp. is distinguished from other species by a less reduced operculogular series. With an estimated total length of 1.72–1.85 m, it is among the largest birgeriids. We confirm that Birgeria encompasses species with either two or three rows of teeth on the maxilla and dentary, and suggest that species with three well-developed rows are restricted to the Early Triassic. From the latest Smithian of Palomino Ridge, we present a three-dimensional, partial skull of the longirostrine predator Saurichthys (Saurichthyidae). This and other occurrences indicate that saurichthyids were common in the western USA basin. From the Early late Spathian of Crittenden Springs, we describe a posterior body portion (Actinopterygii indet.). This find is important given the paucity of Spathian osteichthyan sites. We provide a summary of Early Triassic vertebrate occurrences in the United States, concluding that vertebrate fossils remain largely unstudied. The presence of predatory vertebrates in subequatorial latitudes during the Smithian confirms that Early Triassic trophic chains were not shortened and contradicts the ‘equatorial vertebrate eclipse’.
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Guodunites, a low-palaeolatitude and trans-Panthalassic Smithian (Early Triassic) ammonoid genus.
Palaeontology, 2017Co-Authors: Arnaud Brayard, Thomas Brühwiler, Hugo Bucher, Jim JenksAbstract:Based on new, bed-rock controlled material from Oman and Utah, USA, the Early Triassic genus Guodunites, which was recently erected on the basis of scarce specimens from northwestern Guangxi, South China, is now shown to be a representative of Proptychitidae. This solves the question of the previously unknown phylogenetic affinity of this genus. The genus is restricted to the late middle Smithian, and to date, its biogeographical distribution comprises Oman, South China and Utah, thus indicating an essentially low palaeolatitudinal distribution during the Early Triassic. Its palaeobiogeographical distribution further strengthens the existence of significant equatorial faunal exchanges between both sides of the Panthalassa at that time. It also suggests that, in addition to the potential stepping stones represented by Panthalassic terranes, vigorous equatorial oceanic currents must have contributed largely to the dispersal of ammonoids during such time intervals.
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Marine Early Triassic Osteichthyes from Spiti, Indian Himalayas
Swiss Journal of Palaeontology, 2016Co-Authors: Carlo Romano, David Ware, Hugo Bucher, Thomas Brühwiler, Winand BrinkmannAbstract:A new, marine osteichthyan (bony fish) fauna from the Early Triassic of northern India is presented. The material was collected in situ at localities within Pin Valley (Lahaul and Spiti District, Himachal Pradesh, India) and is dated as middle-late Dienerian (one specimen possibly earliest Smithian). The new ichthyofauna includes a lower jaw of the predatory basal ray-finned fish Saurichthys , a nEarly complete specimen of a parasemionotid neopterygian (cf. Watsonulus cf. eugnathoides ), as well as further articulated and disarticulated remains (Actinopterygii indet., Actinistia indet.), and thus comprises the most complete Triassic fish fossils known from the Indian subcontinent. Saurichthys is known from many Triassic localities and reached a global distribution rapidly after the Late Permian mass extinction event. Parasemionotidae, a species-rich family restricted to the Early Triassic, also achieved widespread distribution during this epoch. Comparison of the Spiti material with other parasemionotid species reveals similarities with Watsonulus eugnathoides from Madagascar. However, taxonomic ambiguities within Parasemionotidae prevent a specific attribution of the Spiti specimen. The new material also includes an isolated actinistian urohyal exhibiting morphology distinct from any previously described urohyal. Marine Dienerian black shale deposited on continental shelves are common not only in the Himalayas but also in other geographic regions. Anoxic depositional settings provide ideal preservational conditions for vertebrate fossils, suggesting that additional ichthyofaunas could still be discovered in marine Dienerian strata of other localities. The study of Early Triassic fish assemblages, including the presented one, is fundamental for our understanding of the great osteichthyan diversification after the Late Permian mass extinction event.
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Early Triassic Marine Biotic Recovery: The Predators' Perspective
PLoS ONE, 2014Co-Authors: Torsten M Scheyer, Carlo Romano, James F. Jenks, Hugo BucherAbstract:Examining the geological past of our planet allows us to study periods of severe climatic and biological crises and recoveries, biotic and abiotic ecosystem fluctuations, and faunal and floral turnovers through time. Furthermore, the recovery dynamics of large predators provide a key for evaluation of the pattern and tempo of ecosystem recovery because predators are interpreted to react most sensitively to environmental turbulences. The end-Permian mass extinction was the most severe crisis experienced by life on Earth, and the common paradigm persists that the biotic recovery from the extinction event was unusually slow and occurred in a step-wise manner, lasting up to eight to nine million years well into the Early Middle Triassic (Anisian) in the oceans, and even longer in the terrestrial realm. Here we survey the global distribution and size spectra of Early Triassic and Anisian marine predatory vertebrates (fishes, amphibians and reptiles) to elucidate the height of trophic pyramids in the aftermath of the end-Permian event. The survey of body size was done by compiling maximum standard lengths for the bony fishes and some cartilaginous fishes, and total size (estimates) for the tetrapods. The distribution and size spectra of the latter are difficult to assess because of preservation artifacts and are thus mostly discussed qualitatively. The data nevertheless demonstrate that no significant size increase of predators is observable from the Early Triassic to the Anisian, as would be expected from the prolonged and stepwise trophic recovery model. The data further indicate that marine ecosystems characterized by multiple trophic levels existed from the earliest Early Triassic onwards. However, a major change in the taxonomic composition of predatory guilds occurred less than two million years after the end-Permian extinction event, in which a transition from fish/amphibian to fish/reptile-dominated higher trophic levels within ecosystems became apparent.
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Early Triassic gastropods from Salt Range, Pakistan
Bulletin of Geosciences, 2013Co-Authors: Andrzej Kaim, Alexander Nützel, Michael Hautmann, Hugo BucherAbstract:Five gastropod species are described from the Early Triassic (Smithian, Spathian) of the Salt Range in Pakistan, which is the first detailed documentation of gastropods from this key area of the Palaeozoic-Mesozoic transition. Bellerophontoidea are represented by Warthia hisakatsui. Bellerophontoidea were widespread in the Paleozoic and had their last appearance in the Early Smithian. Anisian and later reports of this group are discussed, but currently remain doubtful. Soleniscidae, a typical Late Palaeozoic caenogastropod family, are present with two new species: Strobeus batteni and S. pakistanensis. The neritimorph genus Naticopsis and the caenogastropod Coelostylina are present with one species each, provisionally treated in open nomenclature. Naticopsis? sp. shows preservation of original colour patterns, which is very rare in Early Triassic gastropods. All identified genera originated during the Paleozoic (perhaps with the exception of Coelostylina) and are thus survivors or holdovers. Warthia and Strobeus survived the end-Permian mass extinction but went extinct during the Smithian when environmental conditions deteriorated again
Anne-sabine Grosjean - One of the best experts on this subject based on the ideXlab platform.
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Early Triassic environmental dynamics and microbial development during the Smithian–Spathian transition (Lower Weber Canyon, Utah, USA).
Sedimentary Geology, 2018Co-Authors: Anne-sabine Grosjean, James F. Jenks, Kevin G. Bylund, Gwénaël Caravaca, Nicolas Olivier, Gilles Escarguel, Emmanuel Fara, Emmanuelle Vennin, Christophe Thomazo, Daniel A. StephenAbstract:The Early Triassic biotic recovery following the end-Permian mass extinction is well documented in the Smithian–Spathian Thaynes Group of the western USA basin. This sedimentary succession is commonly interpreted as recording harsh conditions of various shallow marine environments where microbial structures flourished. However, recent studies questioned the relevance of the classical view of long-lasting deleterious post-crisis conditions and suggested a rapid diversification of some marine ecosystems during the Early Triassic. Using field and microfacies analyses, we investigate a well-preserved Early Triassic marine sedimentary succession in Lower Weber Canyon (Utah, USA). The identification of microbial structures and their depositional settings provide insights on factors controlling their morphologies and distribution. The Lower Weber Canyon sediments record the vertical evolution of depositional environments from a middle Smithian microbial and dolosiliciclastic peritidal system to a late Smithian-Early Spathian bioclastic, muddy mid ramp. The microbial deposits are interpreted as Microbially Induced Sedimentary Structures (MISS) that developed either (1) in a subtidal mid ramp where microbial wrinkles and chips are associated with megaripples characterizing hydrodynamic conditions of lower flow regime, or (2) in protected areas of inter- to subtidal inner ramp where they formed laminae and domal structures. Integrated with other published data, our investigations highlight that the distribution of these microbial structures was influenced by the combined effects of bathymetry, hydrodynamic conditions, lithology of the substrat physico-chemical characteristics of the depositional environment and by the regional relative sea-level fluctuations. Thus, we suggest that local environmental factors and basin dynamics primarily controlled the modalities of microbial development and preservation during the Early Triassic in the western USA basin.
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Early Triassic environmental dynamics and microbial development during the smithian spathian transition lower weber canyon utah usa
Sedimentary Geology, 2018Co-Authors: Kevin G. Bylund, Gwénaël Caravaca, Nicolas Olivier, Gilles Escarguel, Emmanuel Fara, Emmanuelle Vennin, Anne-sabine Grosjean, Christophe Thomazo, James F. JenksAbstract:The Early Triassic biotic recovery following the end-Permian mass extinction is well documented in the Smithian–Spathian Thaynes Group of the western USA basin. This sedimentary succession is commonly interpreted as recording harsh conditions of various shallow marine environments where microbial structures flourished. However, recent studies questioned the relevance of the classical view of long-lasting deleterious post-crisis conditions and suggested a rapid diversification of some marine ecosystems during the Early Triassic. Using field and microfacies analyses, we investigate a well-preserved Early Triassic marine sedimentary succession in Lower Weber Canyon (Utah, USA). The identification of microbial structures and their depositional settings provide insights on factors controlling their morphologies and distribution. The Lower Weber Canyon sediments record the vertical evolution of depositional environments from a middle Smithian microbial and dolosiliciclastic peritidal system to a late Smithian-Early Spathian bioclastic, muddy mid ramp. The microbial deposits are interpreted as Microbially Induced Sedimentary Structures (MISS) that developed either (1) in a subtidal mid ramp where microbial wrinkles and chips are associated with megaripples characterizing hydrodynamic conditions of lower flow regime, or (2) in protected areas of inter- to subtidal inner ramp where they formed laminae and domal structures. Integrated with other published data, our investigations highlight that the distribution of these microbial structures was influenced by the combined effects of bathymetry, hydrodynamic conditions, lithology of the substrat physico-chemical characteristics of the depositional environment and by the regional relative sea-level fluctuations. Thus, we suggest that local environmental factors and basin dynamics primarily controlled the modalities of microbial development and preservation during the Early Triassic in the western USA basin.
Arnaud Brayard - One of the best experts on this subject based on the ideXlab platform.
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Guodunites, a low-palaeolatitude and trans-Panthalassic Smithian (Early Triassic) ammonoid genus.
Palaeontology, 2017Co-Authors: Arnaud Brayard, Thomas Brühwiler, Hugo Bucher, Jim JenksAbstract:Based on new, bed-rock controlled material from Oman and Utah, USA, the Early Triassic genus Guodunites, which was recently erected on the basis of scarce specimens from northwestern Guangxi, South China, is now shown to be a representative of Proptychitidae. This solves the question of the previously unknown phylogenetic affinity of this genus. The genus is restricted to the late middle Smithian, and to date, its biogeographical distribution comprises Oman, South China and Utah, thus indicating an essentially low palaeolatitudinal distribution during the Early Triassic. Its palaeobiogeographical distribution further strengthens the existence of significant equatorial faunal exchanges between both sides of the Panthalassa at that time. It also suggests that, in addition to the potential stepping stones represented by Panthalassic terranes, vigorous equatorial oceanic currents must have contributed largely to the dispersal of ammonoids during such time intervals.
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Unexpected Early Triassic marine ecosystem and the rise of the Modern evolutionary fauna.
Science Advances, 2017Co-Authors: Arnaud Brayard, James F. Jenks, Kevin G. Bylund, Nicolas Olivier, Laurel J. Krumenacker, Joseph P. Botting, Emmanuel Fara, Emmanuelle Vennin, Nicolas Goudemand, Thomas SaucèdeAbstract:In the wake of the end-Permian mass extinction, the Early Triassic (~251.9 to 247 million years ago) is portrayed as an environmentally unstable interval characterized by several biotic crises and heavily depauperate marine benthic ecosystems. We describe a new fossil assemblage—the Paris Biota—from the earliest Spathian (middle Olenekian, ~250.6 million years ago) of the Bear Lake area, southeastern Idaho, USA. This highly diversified assemblage documents a remarkably complex marine ecosystem including at least seven phyla and 20 distinct metazoan orders, along with algae. Most unexpectedly, it combines Early Paleozoic and middle Mesozoic taxa previously unknown from the Triassic strata, among which are primitive Cambrian-Ordovician leptomitid sponges (a 200–million year Lazarus taxon) and gladius-bearing coleoid cephalopods, a poorly documented group before the Jurassic (~50 million years after the Early Triassic). Additionally, the crinoid and ophiuroid specimens show derived anatomical characters that were thought to have evolved much later. Unlike previous works that suggested a sluggish postcrisis recovery and a low diversity for the Early Triassic benthic organisms, the unexpected composition of this exceptional assemblage points toward an Early and rapid post-Permian diversification for these clades. Overall, it illustrates a phylogenetically diverse, functionally complex, and trophically multileveled marine ecosystem, from primary producers up to top predators and potential scavengers. Hence, the Paris Biota highlights the key evolutionary position of Early Triassic fossil ecosystems in the transition from the Paleozoic to the Modern marine evolutionary fauna at the dawn of the Mesozoic era.
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Gastropod evidence against the Early Triassic Lilliput effect.
Geology, 2010Co-Authors: Arnaud Brayard, Jim Jenks, Kevin G. Bylund, Alexander Nützel, Daniel A. Stephen, Hugo BucherAbstract:Size reduction in the aftermath of the Permian-Triassic mass extinction event has repeatedly been described for various marine organisms, including gastropods (the Lilliput effect). A Smithian gastropod assemblage from Utah, USA, reveals numerous large-sized specimens of different genera as high as 70 mm, the largest ever reported from the Early Triassic. Other gastropods reported from Serbia and Italy are also as large as 35 mm. Size frequency distributions of the studied assemblages indicate that they were not unusually small when compared with later Mesozoic and modern faunas. The occurrence of large-sized gastropods less than 2 Ma after the Permian-Triassic mass extinction refutes the Lilliput hypothesis in this clade, at least for the last ~75% of the Early Triassic.
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Smithian (Early Triassic) Ammonoid Faunas from Northwestern Guangxi (South China): Taxonomy and Biochronology
2009Co-Authors: Arnaud Brayard, Hugo BucherAbstract:The highly fossiliferous succession of Smithian (Early Triassic) ammonoids from northwestern Guangxi (South China) provides a key equatorial record, at the boundary between Tethys and Panthalassa. After the end-Permian extinction, ammonoids reached their first major diversity peak during Smithian times, coupled with a marked contrast in their latitudinal distribution. This monograph contains a part of the fundamental taxonomic and biostratigraphic data of a more comprehensive research project addressing patterns of recovery in time and space of Early Triassic ammonoids and other marine clades, in conjunction with global paleoceanographic and paleoclimatic changes.
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timing of the Early Triassic carbon cycle perturbations inferred from new u pb ages and ammonoid biochronozones
Earth and Planetary Science Letters, 2007Co-Authors: Thomas Galfetti, Arnaud Brayard, Hugo Bucher, Thomas Brühwiler, Nicolas Goudemand, Maria Ovtcharova, Urs Schaltegger, Helmut Weissert, Peter A. Hochuli, Fabrice CordeyAbstract:Based on analyses of single, thermally annealed and chemically abraded zircons, a new high-precision U–Pb age of 251.22± 0.20 Ma is established for a volcanic ash layer within the “Kashmirites densistriatus beds” of Early Smithian age (Early Triassic) from the Luolou Formation (northwestern Guangxi, South China). This new date, together with recalculated uncertainties of previous U– Pb ages from the same section [M. Ovtcharova, H. Bucher, U. Schaltegger, T. Galfetti, A. Brayard, J. Guex. New Early to Middle Triassic U–Pb ages from South China: calibration with ammonoid biochronozones and implications for the timing of the Triassic biotic recovery. Earth Planet. Sci. Lett. 243 (2006) 463–475.] allows constraining the time framework of the Early Triassic and leads to an estimated duration of (i) ca. 0.7±0.6 My for the Smithian and (ii) a maximal duration of ca. 1.4±0.4 My for the Griesbachian– Dienerian time interval. The new U–Pb age considerably reduces the absolute age gap comprised between the Permian–Triassic boundary and the Spathian (late Early Triassic). The new age framework provides the basis for the calibration of a new carbonate carbon isotope and ammonoid records of the Early Triassic Luolou Fm., which in turn are of high significance for global correlations and for carbon cycle modeling. This calibration indicates that the most significant and fastest Early Triassic carbon isotope perturbations occur between the earliest Smithian and the Early Spathian, thus spanning a time interval of about 1 My. Whatever caused these carbon cycle shifts of high intensity and short duration, there is evidence for connections between these fluctuations, the pulsate recovery of ammonoids and conodonts as well as climate changes.
James F. Jenks - One of the best experts on this subject based on the ideXlab platform.
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Marine Early Triassic Actinopterygii from the Candelaria Hills (Esmeralda County, Nevada, USA)
Journal of Paleontology, 2019Co-Authors: Carlo Romano, Adriana López-arbarello, David Ware, James F. Jenks, Winand BrinkmannAbstract:A new locality for low-latitudinal, Early Triassic fishes was discovered in the Candelaria Hills, southwestern Nevada (USA). The fossils are derived from the lower Candelaria Formation, which was deposited during the middle–late Dienerian (late Induan), ca. 500 ka after the Permian-Triassic boundary mass extinction event. The articulated and disarticulated Osteichthyes (bony fishes), encompassing both Actinistia (coelacanths) and Actinopterygii (ray-fins), are preserved in large, silicified concretions that also contain rare coprolites. We describe the first actinopterygians from the Candelaria Hills. The specimens are referred to Pteronisculus nevadanus new species (Turseoidae?), Ardoreosomus occidentalis new genus new species (Ptycholepidae), the stem neopterygian Candelarialepis argentus new genus new species (Parasemionotidae), and Actinopterygii indet. representing additional taxa. Ardoreosomus n. gen. resembles other ptycholepids, but differs in its more angulate hyomandibula and lack of an elongate opercular process. Candelarialepis n. gen. is one of the largest parasemionotids, distinguished by its bipartite preopercle and scale ornamentation. Presented new species belong to genera ( Pteronisculus ) or families (Ptycholepidae, Parasemionotidae) that radiated globally after the mass extinction, thus underlining the striking similarities between Early Triassic (pre-Spathian) osteichthyan assemblages. The current data suggest that the diversity of low-latitudinal, Early Triassic bony fishes may have been greater than indicated thus far by the fossil record, probably due to sampling or taphonomic failure. All 24 fossils from the Candelaria Hills represent mid-sized or large osteichthyans, confirming the obvious absence of very small species (≤ 10 cm adult body length) in the beginning of the Mesozoic Era—even in low latitudes. UUID: http://zoobank.org/6a66ac96-d6b7-4617-94db-5a93cdb14215
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Early Triassic environmental dynamics and microbial development during the Smithian–Spathian transition (Lower Weber Canyon, Utah, USA).
Sedimentary Geology, 2018Co-Authors: Anne-sabine Grosjean, James F. Jenks, Kevin G. Bylund, Gwénaël Caravaca, Nicolas Olivier, Gilles Escarguel, Emmanuel Fara, Emmanuelle Vennin, Christophe Thomazo, Daniel A. StephenAbstract:The Early Triassic biotic recovery following the end-Permian mass extinction is well documented in the Smithian–Spathian Thaynes Group of the western USA basin. This sedimentary succession is commonly interpreted as recording harsh conditions of various shallow marine environments where microbial structures flourished. However, recent studies questioned the relevance of the classical view of long-lasting deleterious post-crisis conditions and suggested a rapid diversification of some marine ecosystems during the Early Triassic. Using field and microfacies analyses, we investigate a well-preserved Early Triassic marine sedimentary succession in Lower Weber Canyon (Utah, USA). The identification of microbial structures and their depositional settings provide insights on factors controlling their morphologies and distribution. The Lower Weber Canyon sediments record the vertical evolution of depositional environments from a middle Smithian microbial and dolosiliciclastic peritidal system to a late Smithian-Early Spathian bioclastic, muddy mid ramp. The microbial deposits are interpreted as Microbially Induced Sedimentary Structures (MISS) that developed either (1) in a subtidal mid ramp where microbial wrinkles and chips are associated with megaripples characterizing hydrodynamic conditions of lower flow regime, or (2) in protected areas of inter- to subtidal inner ramp where they formed laminae and domal structures. Integrated with other published data, our investigations highlight that the distribution of these microbial structures was influenced by the combined effects of bathymetry, hydrodynamic conditions, lithology of the substrat physico-chemical characteristics of the depositional environment and by the regional relative sea-level fluctuations. Thus, we suggest that local environmental factors and basin dynamics primarily controlled the modalities of microbial development and preservation during the Early Triassic in the western USA basin.
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Early Triassic environmental dynamics and microbial development during the smithian spathian transition lower weber canyon utah usa
Sedimentary Geology, 2018Co-Authors: Kevin G. Bylund, Gwénaël Caravaca, Nicolas Olivier, Gilles Escarguel, Emmanuel Fara, Emmanuelle Vennin, Anne-sabine Grosjean, Christophe Thomazo, James F. JenksAbstract:The Early Triassic biotic recovery following the end-Permian mass extinction is well documented in the Smithian–Spathian Thaynes Group of the western USA basin. This sedimentary succession is commonly interpreted as recording harsh conditions of various shallow marine environments where microbial structures flourished. However, recent studies questioned the relevance of the classical view of long-lasting deleterious post-crisis conditions and suggested a rapid diversification of some marine ecosystems during the Early Triassic. Using field and microfacies analyses, we investigate a well-preserved Early Triassic marine sedimentary succession in Lower Weber Canyon (Utah, USA). The identification of microbial structures and their depositional settings provide insights on factors controlling their morphologies and distribution. The Lower Weber Canyon sediments record the vertical evolution of depositional environments from a middle Smithian microbial and dolosiliciclastic peritidal system to a late Smithian-Early Spathian bioclastic, muddy mid ramp. The microbial deposits are interpreted as Microbially Induced Sedimentary Structures (MISS) that developed either (1) in a subtidal mid ramp where microbial wrinkles and chips are associated with megaripples characterizing hydrodynamic conditions of lower flow regime, or (2) in protected areas of inter- to subtidal inner ramp where they formed laminae and domal structures. Integrated with other published data, our investigations highlight that the distribution of these microbial structures was influenced by the combined effects of bathymetry, hydrodynamic conditions, lithology of the substrat physico-chemical characteristics of the depositional environment and by the regional relative sea-level fluctuations. Thus, we suggest that local environmental factors and basin dynamics primarily controlled the modalities of microbial development and preservation during the Early Triassic in the western USA basin.
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Marine Early Triassic Actinopterygii from Elko County (Nevada, USA): implications for the Smithian equatorial vertebrate eclipse
Journal of Paleontology, 2017Co-Authors: Carlo Romano, James F. Jenks, Romain Jattiot, Kevin G. Bylund, Torsten M Scheyer, Hugo BucherAbstract:The Early Triassic vertebrate record from low paleolatitudes is spotty, which led to the notion of an ‘equatorial vertebrate eclipse’ during the Smithian. Here we present articulated ray-finned fishes (Actinopterygii), collected from the marine Lower Triassic Thaynes Group at three new localities in Elko County (Nevada, USA), which were deposited within the equatorial zone. From the Smithian of the Winecup Ranch, we describe two partial skulls of the predatory actinopterygian Birgeria (Birgeriidae), attributed to B. americana new species and Birgeria sp. Birgeria americana n. sp. is distinguished from other species by a less reduced operculogular series. With an estimated total length of 1.72–1.85 m, it is among the largest birgeriids. We confirm that Birgeria encompasses species with either two or three rows of teeth on the maxilla and dentary, and suggest that species with three well-developed rows are restricted to the Early Triassic. From the latest Smithian of Palomino Ridge, we present a three-dimensional, partial skull of the longirostrine predator Saurichthys (Saurichthyidae). This and other occurrences indicate that saurichthyids were common in the western USA basin. From the Early late Spathian of Crittenden Springs, we describe a posterior body portion (Actinopterygii indet.). This find is important given the paucity of Spathian osteichthyan sites. We provide a summary of Early Triassic vertebrate occurrences in the United States, concluding that vertebrate fossils remain largely unstudied. The presence of predatory vertebrates in subequatorial latitudes during the Smithian confirms that Early Triassic trophic chains were not shortened and contradicts the ‘equatorial vertebrate eclipse’.
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Unexpected Early Triassic marine ecosystem and the rise of the Modern evolutionary fauna.
Science Advances, 2017Co-Authors: Arnaud Brayard, James F. Jenks, Kevin G. Bylund, Nicolas Olivier, Laurel J. Krumenacker, Joseph P. Botting, Emmanuel Fara, Emmanuelle Vennin, Nicolas Goudemand, Thomas SaucèdeAbstract:In the wake of the end-Permian mass extinction, the Early Triassic (~251.9 to 247 million years ago) is portrayed as an environmentally unstable interval characterized by several biotic crises and heavily depauperate marine benthic ecosystems. We describe a new fossil assemblage—the Paris Biota—from the earliest Spathian (middle Olenekian, ~250.6 million years ago) of the Bear Lake area, southeastern Idaho, USA. This highly diversified assemblage documents a remarkably complex marine ecosystem including at least seven phyla and 20 distinct metazoan orders, along with algae. Most unexpectedly, it combines Early Paleozoic and middle Mesozoic taxa previously unknown from the Triassic strata, among which are primitive Cambrian-Ordovician leptomitid sponges (a 200–million year Lazarus taxon) and gladius-bearing coleoid cephalopods, a poorly documented group before the Jurassic (~50 million years after the Early Triassic). Additionally, the crinoid and ophiuroid specimens show derived anatomical characters that were thought to have evolved much later. Unlike previous works that suggested a sluggish postcrisis recovery and a low diversity for the Early Triassic benthic organisms, the unexpected composition of this exceptional assemblage points toward an Early and rapid post-Permian diversification for these clades. Overall, it illustrates a phylogenetically diverse, functionally complex, and trophically multileveled marine ecosystem, from primary producers up to top predators and potential scavengers. Hence, the Paris Biota highlights the key evolutionary position of Early Triassic fossil ecosystems in the transition from the Paleozoic to the Modern marine evolutionary fauna at the dawn of the Mesozoic era.
Kevin G. Bylund - One of the best experts on this subject based on the ideXlab platform.
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Early Triassic environmental dynamics and microbial development during the Smithian–Spathian transition (Lower Weber Canyon, Utah, USA).
Sedimentary Geology, 2018Co-Authors: Anne-sabine Grosjean, James F. Jenks, Kevin G. Bylund, Gwénaël Caravaca, Nicolas Olivier, Gilles Escarguel, Emmanuel Fara, Emmanuelle Vennin, Christophe Thomazo, Daniel A. StephenAbstract:The Early Triassic biotic recovery following the end-Permian mass extinction is well documented in the Smithian–Spathian Thaynes Group of the western USA basin. This sedimentary succession is commonly interpreted as recording harsh conditions of various shallow marine environments where microbial structures flourished. However, recent studies questioned the relevance of the classical view of long-lasting deleterious post-crisis conditions and suggested a rapid diversification of some marine ecosystems during the Early Triassic. Using field and microfacies analyses, we investigate a well-preserved Early Triassic marine sedimentary succession in Lower Weber Canyon (Utah, USA). The identification of microbial structures and their depositional settings provide insights on factors controlling their morphologies and distribution. The Lower Weber Canyon sediments record the vertical evolution of depositional environments from a middle Smithian microbial and dolosiliciclastic peritidal system to a late Smithian-Early Spathian bioclastic, muddy mid ramp. The microbial deposits are interpreted as Microbially Induced Sedimentary Structures (MISS) that developed either (1) in a subtidal mid ramp where microbial wrinkles and chips are associated with megaripples characterizing hydrodynamic conditions of lower flow regime, or (2) in protected areas of inter- to subtidal inner ramp where they formed laminae and domal structures. Integrated with other published data, our investigations highlight that the distribution of these microbial structures was influenced by the combined effects of bathymetry, hydrodynamic conditions, lithology of the substrat physico-chemical characteristics of the depositional environment and by the regional relative sea-level fluctuations. Thus, we suggest that local environmental factors and basin dynamics primarily controlled the modalities of microbial development and preservation during the Early Triassic in the western USA basin.
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Early Triassic environmental dynamics and microbial development during the smithian spathian transition lower weber canyon utah usa
Sedimentary Geology, 2018Co-Authors: Kevin G. Bylund, Gwénaël Caravaca, Nicolas Olivier, Gilles Escarguel, Emmanuel Fara, Emmanuelle Vennin, Anne-sabine Grosjean, Christophe Thomazo, James F. JenksAbstract:The Early Triassic biotic recovery following the end-Permian mass extinction is well documented in the Smithian–Spathian Thaynes Group of the western USA basin. This sedimentary succession is commonly interpreted as recording harsh conditions of various shallow marine environments where microbial structures flourished. However, recent studies questioned the relevance of the classical view of long-lasting deleterious post-crisis conditions and suggested a rapid diversification of some marine ecosystems during the Early Triassic. Using field and microfacies analyses, we investigate a well-preserved Early Triassic marine sedimentary succession in Lower Weber Canyon (Utah, USA). The identification of microbial structures and their depositional settings provide insights on factors controlling their morphologies and distribution. The Lower Weber Canyon sediments record the vertical evolution of depositional environments from a middle Smithian microbial and dolosiliciclastic peritidal system to a late Smithian-Early Spathian bioclastic, muddy mid ramp. The microbial deposits are interpreted as Microbially Induced Sedimentary Structures (MISS) that developed either (1) in a subtidal mid ramp where microbial wrinkles and chips are associated with megaripples characterizing hydrodynamic conditions of lower flow regime, or (2) in protected areas of inter- to subtidal inner ramp where they formed laminae and domal structures. Integrated with other published data, our investigations highlight that the distribution of these microbial structures was influenced by the combined effects of bathymetry, hydrodynamic conditions, lithology of the substrat physico-chemical characteristics of the depositional environment and by the regional relative sea-level fluctuations. Thus, we suggest that local environmental factors and basin dynamics primarily controlled the modalities of microbial development and preservation during the Early Triassic in the western USA basin.
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Marine Early Triassic Actinopterygii from Elko County (Nevada, USA): implications for the Smithian equatorial vertebrate eclipse
Journal of Paleontology, 2017Co-Authors: Carlo Romano, James F. Jenks, Romain Jattiot, Kevin G. Bylund, Torsten M Scheyer, Hugo BucherAbstract:The Early Triassic vertebrate record from low paleolatitudes is spotty, which led to the notion of an ‘equatorial vertebrate eclipse’ during the Smithian. Here we present articulated ray-finned fishes (Actinopterygii), collected from the marine Lower Triassic Thaynes Group at three new localities in Elko County (Nevada, USA), which were deposited within the equatorial zone. From the Smithian of the Winecup Ranch, we describe two partial skulls of the predatory actinopterygian Birgeria (Birgeriidae), attributed to B. americana new species and Birgeria sp. Birgeria americana n. sp. is distinguished from other species by a less reduced operculogular series. With an estimated total length of 1.72–1.85 m, it is among the largest birgeriids. We confirm that Birgeria encompasses species with either two or three rows of teeth on the maxilla and dentary, and suggest that species with three well-developed rows are restricted to the Early Triassic. From the latest Smithian of Palomino Ridge, we present a three-dimensional, partial skull of the longirostrine predator Saurichthys (Saurichthyidae). This and other occurrences indicate that saurichthyids were common in the western USA basin. From the Early late Spathian of Crittenden Springs, we describe a posterior body portion (Actinopterygii indet.). This find is important given the paucity of Spathian osteichthyan sites. We provide a summary of Early Triassic vertebrate occurrences in the United States, concluding that vertebrate fossils remain largely unstudied. The presence of predatory vertebrates in subequatorial latitudes during the Smithian confirms that Early Triassic trophic chains were not shortened and contradicts the ‘equatorial vertebrate eclipse’.
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Unexpected Early Triassic marine ecosystem and the rise of the Modern evolutionary fauna.
Science Advances, 2017Co-Authors: Arnaud Brayard, James F. Jenks, Kevin G. Bylund, Nicolas Olivier, Laurel J. Krumenacker, Joseph P. Botting, Emmanuel Fara, Emmanuelle Vennin, Nicolas Goudemand, Thomas SaucèdeAbstract:In the wake of the end-Permian mass extinction, the Early Triassic (~251.9 to 247 million years ago) is portrayed as an environmentally unstable interval characterized by several biotic crises and heavily depauperate marine benthic ecosystems. We describe a new fossil assemblage—the Paris Biota—from the earliest Spathian (middle Olenekian, ~250.6 million years ago) of the Bear Lake area, southeastern Idaho, USA. This highly diversified assemblage documents a remarkably complex marine ecosystem including at least seven phyla and 20 distinct metazoan orders, along with algae. Most unexpectedly, it combines Early Paleozoic and middle Mesozoic taxa previously unknown from the Triassic strata, among which are primitive Cambrian-Ordovician leptomitid sponges (a 200–million year Lazarus taxon) and gladius-bearing coleoid cephalopods, a poorly documented group before the Jurassic (~50 million years after the Early Triassic). Additionally, the crinoid and ophiuroid specimens show derived anatomical characters that were thought to have evolved much later. Unlike previous works that suggested a sluggish postcrisis recovery and a low diversity for the Early Triassic benthic organisms, the unexpected composition of this exceptional assemblage points toward an Early and rapid post-Permian diversification for these clades. Overall, it illustrates a phylogenetically diverse, functionally complex, and trophically multileveled marine ecosystem, from primary producers up to top predators and potential scavengers. Hence, the Paris Biota highlights the key evolutionary position of Early Triassic fossil ecosystems in the transition from the Paleozoic to the Modern marine evolutionary fauna at the dawn of the Mesozoic era.
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Gastropod evidence against the Early Triassic Lilliput effect.
Geology, 2010Co-Authors: Arnaud Brayard, Jim Jenks, Kevin G. Bylund, Alexander Nützel, Daniel A. Stephen, Hugo BucherAbstract:Size reduction in the aftermath of the Permian-Triassic mass extinction event has repeatedly been described for various marine organisms, including gastropods (the Lilliput effect). A Smithian gastropod assemblage from Utah, USA, reveals numerous large-sized specimens of different genera as high as 70 mm, the largest ever reported from the Early Triassic. Other gastropods reported from Serbia and Italy are also as large as 35 mm. Size frequency distributions of the studied assemblages indicate that they were not unusually small when compared with later Mesozoic and modern faunas. The occurrence of large-sized gastropods less than 2 Ma after the Permian-Triassic mass extinction refutes the Lilliput hypothesis in this clade, at least for the last ~75% of the Early Triassic.
