Arnaud Brayard

University of Burgundy | UB · Unité Mixte de Recherche Biogéosciences

The geological record of marine animal biodiversity reflects the interplay between changing rates of speciation versus extinction. Compared to mass extinctions, background extinctions have received little attention. To disentangle the different contributions of global climate state, continental configuration, and atmospheric oxygen concentration (p...

Mantis shrimps (Stomatopoda) are marine benthic predators well known for their raptorial claws that have, through time, evolved into unique structures with exceptional stunning, piercing or even dismembering functions. Known since the Carboniferous, Stomatopoda fossils have started providing insights into the rise of these predators, however, major...

Knowledge of the early evolution of post-Palaeozoic crinoids mainly relies on the well-preserved and abundant material sampled in Triassic Konservat-Lagerstätten such as those from the Anisian Muschelkalk (Middle Triassic) of the Germanic Basin. These crinoid-bearing Lagerstätten have been central to understanding the rapid evolution and diversific...

Ammonoids are key fossil indexes for Triassic biochronology, as all Triassic stages and substages were initially defined on ammonoid faunas. In recent decades, the temporal resolution of ammonoid biostratigraphical scales for the Early Triassic has been greatly improved. However, many uncertainties in zones correlation and superpositions remain, ma...

Finely preserved fossil assemblages (lagerstätten) provide crucial insights into evolutionary innovations in deep time. We report an exceptionally preserved Early Triassic fossil assemblage, the Guiyang Biota, from the Daye Formation near Guiyang, South China. High-precision uranium-lead dating shows that the age of the Guiyang Biota is 250.83 +0.0...

The Hiraiso Formation of northeast Japan represents an important and under-explored archive of Early Triassic marine ecosystems. Here, we present a palaeoecological analysis of its benthic faunas in order to explore the temporal and spatial variations of diversity, ecological structure and taxonomic composition. In addition, we utilise redox proxie...

We document an upper upper Albian (Mortoniceras rostratum Zone) cephalopod assemblage from Clansayes (Drôme, south-eastern France). Although fossils are rare in local exposures and in the single sampled level, a decade of intensive fossil collecting yielded 290 ammonite and 5 nautilid specimens. In total, we describe 1 spe- cies of nautilid and 24...

We describe here the early Spathian (Early Triassic) Paris Biota decapod fauna from the western USA basin. This fauna contains two taxa of Aegeridae (Dendobranchiata), namely Anisaeger longirostrus n. sp. and Aeger sp. that are the oldest known representatives of their family, thus extending its temporal range by 5 Myr back into the Early Triassic....

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 Triassi...

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 US...

Abstract—We document a relatively small but very important late Griesbachian ammonoid and nautiloid assemblage from the Dinwoody Formation at Crittenden Springs, Elko County, Nevada. This discovery represents the first significant report of late Griesbachian ammonoids in the low-paleolatitudes of eastern Panthalassa, and it also signifies the first...

The biotic recovery following the Permian/Triassic boundary mass extinction was influenced by several secondary extinctions during the Early Triassic, of which the late Smithian crisis is the most severe known for some nekto-pelagic organisms such as ammonoids. The Smithian-Spathian transition is characterized by successive global biotic and enviro...

Thylacocephala (euarthropoda: eucrustacea?) is a group of enigmatic fossil euarthropods, known from at least the silurian to the Cretaceous. The Triassic is considered to be the period during which thylacocephalans were the most diversified with 17 species reported from 19 localities in nine countries. However, Thylacocephala were assumed to be rar...

New Smithian (Early Triassic) ammonoid assemblages were sampled near the Utah/Arizona border. They provide several spatiotemporal constraints on the regional Sinbad Formation showing that the extent of the Smithian sea in the southwestern-most part of the western USA basin is larger than previously expected, reaching northern Arizona and an area ju...

Stable isotope signatures of elements related to life such as carbon and nitrogen can be powerful biomarkers that provide key information on the biological origin of organic remains and their paleoenvironments. Marked advances have been achieved in the last decade in our understanding of the coupled evolution of biological carbon and nitrogen cycli...

Two extensive collections retrieved from West Timor have yielded several astonishingly well-preserved and highly diversified Smithian (Early Triassic) ammonoid faunas (Kashmirites fauna, Owenites fauna, Anasibirites fauna). A population approach on this material, with an emphasis on ontogeny and covariation of morphological characters, led to the u...

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 patholo...

In modern examples of well-developed microbial-dominated deposits associated with metazoan organisms can be currently found in various environments including but not restricted to lagoons in Polynesia (Sprachta et al., 2001), the warm water of the Cuba (e.g., Bouton et al., 2016; Pace et al., 2018), the hypersaline lakes of the Great Salt Lake (USA...

A c. 0.30 m thick cherty limestone bed in the Dalong Formation at Gujiao (Guizhou) has yielded a highly diverse Changhsingian nautiloid assemblage. Its age is late Changhsingian, indicated by the co‐occurring ammonoid Pseudotirolites sp. This assemblage is composed of nine species and five taxa in open nomenclature in nine genera, including one new...

The Early Triassic is generally portrayed as a time of various, high ecological stresses leading to a delayed biotic recovery after the devastating end-Permian mass extinction. This interval is notably characterized by repeated biotic crises (e.g., during the late Smithian), large-scale fluctuations of the global carbon, nitrogen and sulfur cycles...

A new, diverse and complex Early Triassic assemblage was recently discovered west of the town of Paris, Idaho (Bear Lake County), USA. This assemblage has been coined the Paris Biota. Dated earliest Spathian (Olenekian), the Paris Biota provides further evidence that the biotic recovery from the end-Permian mass extinction was well underway ca. 1.5...

Two new genera and species of thylacocephalans (Arthropoda, Thylacocephala), Parisicaris triassica Charbonnier and Ligulacaris parisiana Charbonnier, are described from the early Spathian Paris Biota. These new occurrences are the first reports of thylacocephalans from Triassic rocks in North America. They considerably enlarge the spatiotemporal di...

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...

The end-Permian mass extinction is the largest global-scale event ever recorded; it also corresponds to the expansion of the Modern Evolutionary Fauna, which will lead to present-day ecosystems. The Early Triassic is thus a pivotal interval in the evolution of many marine groups. An exceptionally well-preserved early Spathian fossil assemblage, the...

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...

The transition from the Smithian substage to the Spathian substage of the Olenekian stage of the late Early Triassic was a critical time marked by a series of biological and environmental changes during the multimillion-year recovery interval following the end-Permian mass extinction. However, the Smithian/Spathian boundary (SSB) does not yet have...

Bed-by-bed sampling of the lower portion of the Daye Formation at Gujiao, Guizhou Province, South China, yielded new Griesbachian–Dienerian (Induan, Early Triassic) ammonoid faunas showing a new regional Induan ammonoid succession. This biostratigraphic scheme includes in chronological order the late Griesbachian Ophiceras medium and Jieshaniceras...

The increase of species range sizes towards high latitudes, known as the Rapoport’s rule, remains one of the most debated and poorly understood macroecological patterns. Numerous studies have challenged both its universality and the main mechanism originally proposed to explain it, i.e. the climatic variability hypothesis. Here we study this patter...

The increase in species range size towards high latitudes, known as Rapoport's rule, remains one of the most debated and poorly understood macroecological patterns. Numerous studies have challenged both its universality and the main mechanism originally proposed to explain it: the climatic variability hypothesis. Here, we study this pattern using a...

The increase of species range sizes towards high latitudes, known as the "Rapoport's rule", remains one of the most debated and poorly understood macroecological patterns. Numerous studies have challenged its universality, which led to rename it the "Rapoport effect", as well as the main mechanism originally proposed to explain this pattern, i.e. t...

The end-Permian mass extinction was the most severe extinction in the history of life, wiping out more than 90% of marine species. Only one order of ammonoids survived it on a long term: Ceratitida. These are widely used for the construction of biochronological time scales, and as such play an essential role in our understanding of the biotic crisi...

We present the first quantitative palaeobiogeographical analysis in terms of distribution and abundance of Early Triassic ammonoids from the western USA basin during the Smithian, c. 1 myr after the Permian–Triassic boundary mass extinction. The faunal dataset consists of a taxonomically homogenized compilation of spatial and temporal occurrences a...

We describe an Olenekian (Early Triassic) “fossil squid” belonging to the oldest complex Mesozoic marine biota collected in the Lower Shale unit of the Lower Triassic Thaynes Group in Idaho, USA. The studied specimen shows a tapered structure embedded in a cylindrical soft body. Morphological, ultrastructural and geochemical features of the specime...

The Bonneville Basin is a continental lacustrine system accommodating extensive microbial carbonate deposits corresponding to two distinct phases: the deep Lake Bonneville (30,000 to 11,500 ¹⁴C BP) and the shallow Great Salt Lake (since 11,500 ¹⁴C BP). A characterization of these microbial deposits and their associated sediments provides insights i...

Recurrent microbialite proliferations during the Early Triassic are usually explained by ecological relaxation and abnormal oceanic conditions. Most Early Triassic microbialites are described as single or multiple lithological units without detailed ecological information about lateral and coeval fossiliferous deposits. Exposed rocks along Workman...

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 quest...

We present a comprehensive monographic treatment of all currently known Smithian (Early Triassic) ammonoid taxa from Crittenden Springs. Extensive collection efforts from numerous stratigraphically discontinuous, condensed outcrops over a period spanning four decades has yielded a total of 60 taxa. This activity has also resulted in the recognition...

Important and recurrent perturbations of the carbon isotope signals are recorded during the Early Triassic, in the aftermath of the end-Permian mass extinction (~252 Ma). These perturbations, among the largest observed throughout the Phanerozoic, are most notably represented by a globally recognized couplet of a negative and a positive excursions,...

In the aftermath of the end-Permian mass extinction (~252 Ma), the Early Triassic Sonoma Foreland Basin (SFB) provides excellent sedimentary and fossil records to describe and understand the Early Triassic biotic recovery. Nevertheless, despite its importance, this basin is still poorly constrained and its controlling factors rather unclear. A new...

Intensive sampling of the lower portion of the Thaynes Group within the Palomino Ridge area (northeastern Nevada) yielded abundant and well-preserved Smithian (Early Triassic) ammonoid faunas. Ammonoid taxonomy and a detailed biostratigraphy for this locality are reported herein. One new genus (Palominoceras) and one new species (?Pseudosageceras b...

The Early Triassic is generally portrayed as a time of high ecological stress leading to a delayed biotic recovery in the aftermath of the devastating end-Permian mass extinction. This interval is also characterized by repeated large-scale fluctuations of the global carbon, nitrogen and sulfur cycles, associated with harsh marine conditions includi...

Aim: To test for the phylogenetic conservatism of geographic range size and to explore the effect of the environment on this potential conservatism. Location: The western Tethys Ocean and its surroundings (present-day Europe, the Middle East and North Africa) during the early Pliensbachian (Early Jurassic). Methods: Using 104 localities and 1,765 o...

Supplementary files provided as a complement to the "Early Triassic fluctuations of the global carbon cycle: New evidence from paired carbon isotopes in the western USA basin" article, Global & Planetary Change, 2017.

In the aftermath of the catastrophic end-Permian mass extinction, the Early Triassic records recurrent perturbations in the carbon isotope signal, most notably during the Smithian and through the Smithian/Spathian Boundary (SSB; ~ 1.5 myr after the Permian/Triassic boundary), which show some of the largest excursions of the Phanerozoic. The late Sm...

We describe Superstesaster promissor gen. et sp. nov., a starfish from the Smithian (Early Triassic) of Utah (USA) that fills a major gap in the fossil record of the Asteroidea. The post-Palaeozoic crown group Asteroidea are distinct from any of the diverse Palaeozoic forms. However, current understanding of the Palaeozoic–Mesozoic transition is bl...

Sediments deposited from the Permian–Triassic boundary (~252 Ma) until the end-Smithian (Early Triassic; c. 250.7 Ma) in the Sonoma Foreland Basin show marked thickness variations between its southern (up to c. 250 m thick) and northern (up to c. 550 m thick) parts. This basin formed as a flexural response to the emplacement of the Golconda Allocht...

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...

Supplementary material (text, figures and tables) to: Brayard et al. 2017 - Science Advances 3, e1602159.

-Aim- To describe and analyse asteroid biogeographic patterns in the Southern Ocean (SO) and test whether reproductive strategy (brooder versus broadcaster) can explain distribution patterns at the scale of the entire class. We hypothesize that brooding and broadcasting species display different biogeographic patterns. -Location- Southern Ocean, s...

Geographic range size is a fundamental ecological and evolutionary feature of species that results from a complex interplay of intrinsic (e.g. dispersal ability, ecological tolerance) and extrinsic factors (e.g. environmental features, physical barriers). Using a dataset of 214 ammonite species from the early Pliensbachian of the western Tethys and...

Since the pioneer work of Silberling and Tozer (1968), the western USA basin is known as including an excellent record of Smithian ammonoids. The Smithian is a crucial time interval, recording the first global, major diversification-extinction cycle after the Permian-Triassic boundary mass extinction (PTBME). Our intensive sampling of the lower por...

The Toarcian ammonite genus Porpoceras Buckman, 1911 is a cosmopolitan taxon with an uncertain stratigraphic range. The oldest known occurrence of the genus was reported from the Falciferum Subzone (Early Toarcian) in Morocco, although based on a unique specimen whose taxonomic assignment to the genus Porpoceras remains doubtful. The youngest occur...

The Great Salt Lake is a modern hypersaline lake, in which an extended modern and ancient microbial sedimen- tary system has developed. Detailed mapping based on aerial images and field observations can be used to identify non- random distribution patterns of microbial deposits, such as paleoshorelines associated with extensive polygons or fault- p...

Palaeontological data are key elements for inferring ancestral character states and the assembly of character complexes, but cephalopod fossils preserving soft tissues are very rare. The exceptionally well-preserved, unique specimen of Jurassic Proteroctopus ribeti Fischer & Riou from the Lagerstätte of La-Voulte-sur-Rhône (c. 165 Ma, France) is on...

The Sonoma Foreland Basin was formed as a flexural response to the emplacement of the Golconda Allochthon during the Sonoma Orogeny around the Permian/Triassic boundary (~252 Ma), and it includes an excellent fossil and sedimentary record of the Early Triassic. However, sediments deposited from the Permian/Triassic boundary until the end-Smithian (...

In biogeography, the similarity distance decay (SDD) relationship refers to the decrease in compositional similarity between communities with geographical distance. Although representing one of the most widely used relationships in biogeography, a review of the literature reveals that: (1) SDD is influenced by both spatial extent and sample size; (...

This work focuses on well-exposed Lower Triassic sedimentary rocks in the area of Torrey (south-central Utah, USA). The studied Smithian deposits record a large-scale third order sea-level cycle, which permits a detailed reconstruction of the evolution of depositional settings. During the middle Smithian, peritidal microbial limestones associated w...

The Great Salt Lake, Utah, USA is a shallow, hypersaline, intracontinental lake hosting extensive microbial deposits. At a large spatial scale, the distribution of these deposits is driven by environmental and geodynamical factors (i.e. water-level fluctuations and a fault-related framework). A detailed mapping of the Buffalo Point area, in the nor...

The Great Salt Lake is a modern hypersaline system in which an extended modern and ancient microbial sedimentary system has developed. Detailed mapping based on aerial images and field observations can be used to identify non-random distribution patterns of microbial deposits, such as paleoshorelines associated with extensive polygons or fault-para...

In the aftermath of the end-Permian mass extinction, Early Triassic sediments record some of the largest Phanerozoic carbon isotopic excursions. Among them, a global Smithian-negative carbonate carbon isotope excursion has been identified, followed by an abrupt increase across the Smithian-Spathian boundary (SSB; ~250.8 Myr ago). This chemostratigr...

The Permian and Triassic were key time intervals in the history of life on Earth. Both periods are marked by a series of biotic crises including the most catastrophic of such events, the end-Permian mass extinction, which eventually led to a major turnover from typical Palaeozoic faunas and floras to those that are emblematic for the Mesozoic and C...