Christopher P. A. Smith

Centre National de la Recherche Scientifique

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Arnaud Brayard

Centre National de la Recherche Scientifique

Thomas Laville

Centre National de la Recherche Scientifique

Sylvain Charbonnier

Structure et Instabilité des Génomes

Marie‐Béatrice Forel

Centre National de la Recherche Scientifique

Jérémie Bardin

Sorbonne Université

Nicolas Olivier

Centre National de la Recherche Scientifique

Emmanuel Fara

Centre National de la Recherche Scientifique

Isabelle Kruta

Sorbonne Université

James F. Jenks

Web Vision Centers (United States)

Kevin G. Bylund

American Fork Hospital

Cooperative Institutions

China University of Geosciences

Centre National de la Recherche Scientifique

State Key Laboratory of Biogeology and Environmental Geology

Structure et Instabilité des Génomes

Muséum national d'Histoire naturelle

Institute of Paleoprimatology Human Paleontology Evolution and Paleoenvironments

Biogéosciences

Université de Bourgogne

Sorbonne Université

Centre de recherche en paléontologie - Paris

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Data from: Review of Early Triassic Thylacocephala

Zenodo (CERN European Organization for Nuclear Research) (2020)

Thomas Laville Christopher P. A. Smith Marie‐Béatrice Forel Arnaud Brayard Sylvain Charbonnier

Measurements for Early Triassic Thylacocephala from Madagascar (Dienerian/Smithian), Idaho & Nevada including specimens of Ankitokazocaris acutirostris (7 specimens), Ankitokazocaris triassica (6 specimens), Ligulacaris parisiana (7 specimens) and Paraostenia ambatolokobensis (3 specimens). Script for descriptive statistics is also provided. Measurements were directly done on digital photographs with ImageJ2. When part and counter-part were available, measurements were done on both sides and then averaged.

10.5281/zenodo.4066339

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New evidence from exceptionally “well-preserved” specimens sheds light on the structure of the ammonite brachial crown

Scientific Reports (2021)

Christopher P. A. Smith Neil H. Landman Jérémie Bardin Isabelle Kruta

Abstract Ammonite soft body remains are rarely preserved. One of the biggest enigmas is the morphology of the ammonite brachial crown that has, up till now, never been recovered. Recently, mysterious hook-like structures have been reported in multiple specimens of Scaphitidae, a large family of heteromorph Late Cretaceous ammonites. A previous examination of these structures revealed that they belong to the ammonites. Their nature, however, remained elusive. Here, we exploit tomographic data to study their arrangement in space in order to clarify this matter. After using topological data analyses and comparing their morphology, number, and distribution to other known cephalopod structures, in both extant and extinct taxa, we conclude that these hook-like structures represent part of the brachial crown armature. Therefore, it appears that there are at least three independent evolutionary origins of hooks: in belemnoids, oegospids, and now in ammonites. Finally, we propose for the first time a hypothetical reconstruction of an ammonite brachial crown.

Ammonite

Hook

10.1038/s41598-021-89998-4

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Citations (5)

Review of early Triassic Thylacocephala

HAL (Le Centre pour la Communication Scientifique Directe) (2021)

Thomas Laville Christopher P. A. Smith Marie‐Béatrice Forel Arnaud Brayard Sylvain Charbonnier

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 rare during the Early Triassic until recent discoveries in Japan, Nevada and Idaho, U.S.A. Our study focuses on thylacocephalans from the Early Triassic, especially from Madagascar and Idaho. The revision of previously known taxa from Madagascar provides new important information. A new kind of ornamentation is reported for Paraostenia ambatolokobensis nov. comb., previously assigned to Ostenocaris ambatolokobensis. In addition, Ankitokazocaris acutirostris and Paraostenia ambatolokobensis are only the third and fourth thylacocephalan taxa for which possible cephalic appendages are described. New occurrences of Thylacocephala in Nevada and Idaho, U.S.A., lead to the description of one new taxon and to the reassignement of Parisicaris triassica to Ankitokazocaris triassica nov. comb. Those occurrences provide a significant contribution to the knowledge of Thylacocephala taxonomic diversity and geographic distribution during the Early Triassic. An important revision of Early Triassic thylacocephalan taxa from Japan and China is also performed, including Ankitokazocaris chaohuensis, Ankitokazocaris parva nov. comb., Ankitokazocaris utatsuensis nov. comb. and Paraostenia sp. Overall, the taxonomic diversity of Triassic thylacocephalans has likely been slightly over-estimated (17 species before, 15 now). However, the Triassic represents the richest period in terms of thylacocephalan-bearing outcrops (19 localities from nine countries).

Early Triassic

10.13130/2039-4942/15188

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A Mesozoic fossil lagerstätte from 250.8 million years ago shows a modern-type marine ecosystem

Science (2023)

Xu Dai Joshua H.F.L. Davies Zhiwei Yuan Arnaud Brayard Maria Ovtcharova

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 +0.07/–0.06 million years ago. This is only 1.08 ± 0.08 million years after the severe Permian-Triassic mass extinction, and this assemblage therefore represents the oldest known Mesozoic lagerstätte found so far. The Guiyang Biota comprises at least 12 classes and 19 orders, including diverse fish fauna and malacostracans, revealing a trophically complex marine ecosystem. Therefore, this assemblage demonstrates the rapid rise of modern-type marine ecosystems after the Permian-Triassic mass extinction.

Lagerstätte

Biota

Assemblage (archaeology)

Early Triassic

Marine ecosystem

Extinction (optical mineralogy)

10.1126/science.adf1622

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The Paris Biota decapod (Arthropoda) fauna and the diversity of Triassic decapods

Journal of Paleontology (2022)

Christopher P. A. Smith Sylvain Charbonnier James F. Jenks Kevin G. Bylund Gilles Escarguel

Abstract 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. This fauna also includes two representatives of Glypheida (Pleocyemata) with Litogaster turnbullensis and Pemphix krumenackeri n. sp., confirming for the former and extending for the latter the temporal ranges of their respective superfamilies back to the Early Triassic. Overall, the Paris Biota decapods are some of the oldest known representatives of Decapoda, filling in an important gap in the evolutionary history of this group, especially during the Triassic that marks the early diversification of this clade. Additionally, we compile and provide overviews for all known Triassic decapods, which leads to the revision of four species of Middle and Late Triassic Aegeridae, and to a revised family assignment of a Middle Triassic Glypheida. Based on this refined dataset, we also investigate decapod diversity throughout the Triassic. We show that the apparent increase in decapod taxonomic richness is probably driven by the heterogeneity of the fossil record and/or sampling effort, and that the decapod alpha diversity is actually relatively high as soon as the Early Triassic and remains rather stable throughout the Triassic. UUID: http://zoobank.org/0f435f27-1767-473d-955c-57fe869faa0f

Biota

Early Triassic

Biochronology

Paleoecology

10.1017/jpa.2022.34

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Citations (4)

Exceptional fossil assemblages confirm the existence of complex Early Triassic ecosystems during the early Spathian

Scientific Reports (2021)

Christopher P. A. Smith Thomas Laville Emmanuel Fara Gilles Escarguel Nicolas Olivier

Abstract 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 Spathian. The presence of a well-established marine fauna such as the Paris Biota, as soon as the early Spathian, indicates that the post-PTB biotic recovery and the installation of complex ecosystems probably took place earlier than often assumed, at least at a regional scale.

Biota

Early Triassic

Extinction (optical mineralogy)

10.1038/s41598-021-99056-8

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Citations (15)

Data from: Review of Early Triassic Thylacocephala

Zenodo (CERN European Organization for Nuclear Research) (2020)

Thomas Laville Christopher P. A. Smith Marie‐Béatrice Forel Arnaud Brayard Sylvain Charbonnier

10.5281/zenodo.4066340

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Enigmatic hook‐like structures in Cretaceous ammonites (Scaphitidae)

Palaeontology (2019)

Isabelle Kruta Jérémie Bardin Christopher P. A. Smith Paul Tafforeau Neil H. Landman

Abstract In the last few decades, hook‐like structures have been reported in the Mesozoic ammonite family Scaphitidae. Despite their exceptional preservation and debates about their function, no detailed reconstruction has been available until now. For the first time, we describe the composition and details of the morphology of these structures found in the body chambers of six specimens of the Campanian ammonite Rhaeboceras halli (Meek & Hayden) using high resolution x‐ray imaging. The hook‐like structures are composed of a thin layer of brushite. The base of each hook is open on one side forming an internal cavity, now filled with sediment. The tips of the hooks end in one or two cusps or, rarely, exhibit a blunt end. We used geometric morphometrics to capture the morphological disparity of the bicuspidate morphotypes comprising 98% of the hooks. Principal component analysis revealed chirality among the hooks and a cluster analysis recognized five morphologies. Contrary to the previous interpretation of these structures, we conclude that they are not radular teeth. They are much larger and more variable in size and shape than any known ammonite radulae and completely out of proportion with respect to the size of the jaw. The chirality, the hook‐like shape, and the absence of a size relationship between the hooks and the body chambers in which they occur, lead us to propose that these hooks could represent elements of the brachial crown related to copulatory behaviour. If so, these would be the first reported remnants of brachial crowns in ammonites.

Hook

Ammonite

10.1111/pala.12457

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Citations (10)

The Paris Biota (Spathian, Early Triassic) : At the dawn of modern marine faunas?

Christopher P. A. Smith

Biota

Early Triassic

Source

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