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Sci Adv. 2017 Feb 15;3(2):e1602159. doi: 10.1126/sciadv.1602159. eCollection 2017 Feb.

Unexpected Early Triassic marine ecosystem and the rise of the Modern evolutionary fauna.

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Biogéosciences UMR 6282, CNRS, Université Bourgogne Franche-Comté, 6 Boulevard Gabriel, 21000 Dijon, France.
Department of Earth Sciences, Montana State University, P.O. Box 173480, Bozeman, MT 59717-3480, USA.
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.
1134 Johnson Ridge Lane, West Jordan, UT 84084, USA.
140 South 700 East, Spanish Fork, UT 84660, USA.
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.
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.
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.
Paläontologisches Institut und Museum, Universität Zürich, 8006 Zürich, Switzerland.
Department of Palaeobiology, Swedish Museum of Natural History, P.O. Box 50007, SE-10405 Stockholm, Sweden.
Department of Palaeontology, Natural History Museum Luxembourg, 25 rue Münster, L-2160 Luxembourg, Luxembourg.
Department of Earth Science, Utah Valley University, 800 West University Parkway, Orem, UT 84058, USA.
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.


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.


Early Triassic; End-Permian mass extinction; Idaho; Paris Biota; biotic recovery; marine ecosystems

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