title: Unexpected Early Triassic marine ecosystem and the rise of the Modern evolutionary fauna.
abstract: 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.
authors.affiliation: Biogéosciences UMR 6282, CNRS, Université Bourgogne Franche-Comté, 6 Boulevard Gabriel, 21000 Dijon, France.
authors.forename: Arnaud
authors.identifier: 0000-0003-1304-6553
authors.initials: A
authors.lastname: Brayard
authors.affiliation: Department of Earth Sciences, Montana State University, P.O. Box 173480, Bozeman, MT 59717-3480, USA.
authors.forename: L J
authors.identifier: 0000-0002-5990-3349
authors.initials: LJ
authors.lastname: Krumenacker
authors.affiliation: Nanjing Institute of Geology and Palaeontology, 39 East Beijing Road, Nanjing 210008, China.; Department of Geology, National Museum of Wales, Cathays Park, Cardiff CF10 3NP, U.K.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Botting
authors.affiliation: 1134 Johnson Ridge Lane, West Jordan, UT 84084, USA.
authors.forename: James F
authors.initials: JF
authors.lastname: Jenks
authors.affiliation: 140 South 700 East, Spanish Fork, UT 84660, USA.
authors.forename: Kevin G
authors.initials: KG
authors.lastname: Bylund
authors.affiliation: Biogéosciences UMR 6282, CNRS, Université Bourgogne Franche-Comté, 6 Boulevard Gabriel, 21000 Dijon, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Fara
authors.affiliation: Biogéosciences UMR 6282, CNRS, Université Bourgogne Franche-Comté, 6 Boulevard Gabriel, 21000 Dijon, France.
authors.forename: Emmanuelle
authors.identifier: 0000-0002-5899-0399
authors.initials: E
authors.lastname: Vennin
authors.affiliation: Université Clermont Auvergne, CNRS, IRD, Observatoire de Physique du Globe de Clermont-Ferrand, Laboratoire Magmas et Volcans, 5 rue Kessler, F-63000 Clermont-Ferrand, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Olivier
authors.affiliation: Institute of Functional Genomics of Lyon, École Normale Supérieure de Lyon-CNRS 5242-Institut National de la Recherche Agronomique Unités Sous Contrat INRA USC 1370, 46 allée d'Italie, 69364 Lyon Cedex 07, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Goudemand
authors.affiliation: Biogéosciences UMR 6282, CNRS, Université Bourgogne Franche-Comté, 6 Boulevard Gabriel, 21000 Dijon, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Saucède
authors.affiliation: Muséum national d'Histoire naturelle (MNHN), Centre de Recherche sur la Paléobiodiversité et les Paléoenvironnements (UMR 7207), Sorbonne Universités-MNHN, CNRS, Université Pierre et Marie Curie, 57 rue Cuvier, 75005 Paris, France.
authors.forename: Sylvain
authors.identifier: 0000-0002-9496-3849
authors.initials: S
authors.lastname: Charbonnier
authors.affiliation: Paläontologisches Institut und Museum, Universität Zürich, 8006 Zürich, Switzerland.
authors.forename: Carlo
authors.identifier: 0000-0003-4438-2736
authors.initials: C
authors.lastname: Romano
authors.affiliation: Department of Palaeobiology, Swedish Museum of Natural History, P.O. Box 50007, SE-10405 Stockholm, Sweden.
authors.forename: Larisa
authors.identifier: 0000-0002-1231-2488
authors.initials: L
authors.lastname: Doguzhaeva
authors.affiliation: Department of Palaeontology, Natural History Museum Luxembourg, 25 rue Münster, L-2160 Luxembourg, Luxembourg.
authors.forename: Ben
authors.initials: B
authors.lastname: Thuy
authors.affiliation: Paläontologisches Institut und Museum, Universität Zürich, 8006 Zürich, Switzerland.
authors.forename: Michael
authors.identifier: 0000-0002-7322-8749
authors.initials: M
authors.lastname: Hautmann
authors.affiliation: Department of Earth Science, Utah Valley University, 800 West University Parkway, Orem, UT 84058, USA.
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Stephen
authors.affiliation: Biogéosciences UMR 6282, CNRS, Université Bourgogne Franche-Comté, 6 Boulevard Gabriel, 21000 Dijon, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Thomazo
authors.affiliation: Univ Lyon, Université Claude Bernard Lyon 1, CNRS, ENTPE, UMR 5023 Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés, 27-43 Boulevard du 11 novembre 1918, 69622 Villeurbanne Cedex, France.
authors.forename: Gilles
authors.initials: G
authors.lastname: Escarguel
mesh_terms: D000818:Animals; D059001:Aquatic Organisms / Q000502:physiology*; D005075:Biological Evolution; D017753:Ecosystem; D005580:Fossils; D010802:Phylogeny
keywords: Early Triassic; End-Permian mass extinction; Idaho; Paris Biota; biotic recovery; marine ecosystems