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The Paris biota is an exceptionally diverse Early Triassic (approximately 249 million years ago)[1] fossil assemblage described in 2017 from the Lower Shale Member of the Thaynes Group. It was first discovered in Paris Canyon, west of the town of Paris in Bear Lake County, southeastern Idaho, United States.[2] This biota was later also found in coeval and slightly younger beds in northeastern Nevada (Elko County) and Bear Lake and Caribou counties, southeastern Idaho.[3]
The Paris biota was found in layers dating back to the earliest Spathian, a substage of the Olenekian stage of the Early Triassicepoch. The biostratigraphy is constrained by the presence of the ammonoids Tirolites and Bajarunia, and conodonts.[2][3] The Tirolites/Columbites beds are dated with 248.853±0.086 Ma.[1] The Paris biota was later also discovered in slightly younger beds in Immigrant Canyon, northeastern Nevada, associated with the ammonoid index fossils Prohungarites sp. and Neopopanoceras haugi, which point to a middle–late Spathian age.[3]
Palaeogeography and paleoenvironment
The organisms of the Paris biota lived in a shallow marine epicontinental sea (western USA basin) on the western coast of Pangea. The sites were located in a near-equatorial position during the Early Triassic epoch.[2][3]
Assemblage
The Spathian aged Paris biota is one of the earliest diverse fossil assemblages from the post-extinction interval, about 3 million years[1][4] after the Permian-Triassic mass extinction, and the first one in the wake of the Smithian-Spathian boundary extinction.
The Paris biota comprises fossils belonging to 20 orders or seven phyla: (1) Retaria (foraminifers)[2] (2) sponges, (3) brachiopods (4) mollusks, (5) arthropods, (6) echinoderms and (7) chordates (vertebrates). The assemblage also contains fossil algae and coprolites (trace fossils). Ammonoids and bivalves dominate the fauna.[2] It combines Palaeozoic survivors with members of the Modern evolutionary fauna (i.e., groups that are typical for the Mesozoic and Cenozoic). The Paris biota therefore provides a glimpse at the faunal turnover associated with the largest mass extinction in Earth's history. For example, the biota includes leptomitidprotomonaxonid sponges, a group that is otherwise known from the early Paleozoicera (e.g. from the CambrianBurgess Shale of western Canada). Among the modern clades, it contains a gladius-bearing coleoid cephalopod (Idahoteuthis).
The preservation of Paris biota organisms is considered taxon-dependent, but is not fully understood.[5] The study of some fossils could be improved using synchrotron μXRF imaging.[6]
Most organisms of the Paris biota were described in a thematic issue of the journal Geobios in 2019,[7] but new taxa were also subsequently described.
In 2023, another diverse post-extinction biota was presented from South China, the Dienerian aged Guiyang biota,[8] which includes fossils belonging to twelve classes and 19 orders. The Early Triassic is generally considered as an environmentally unstable and diversity-poor interval,[2] highlighting the importance of the discovery of such diverse lagerstätten.
The following taxa (animals sorted by phylum) were either reported or described from the Paris biota (not listed are the foraminifera and conodonts, which have not yet been described):
↑Iniesto, Miguel; Thomazo, Christophe; Fara, Emmanuel; the Paris Biota Team (2019). "Deciphering the exceptional preservation of the Early Triassic Paris Biota (Bear Lake County, Idaho, USA)". Geobios54: 81–93. doi:10.1016/j.geobios.2019.04.002. Bibcode: 2019Geobi..54...81I.
↑Brayard, Arnaud; Gueriau, Pierre; Thoury, Mathieu; Escarguel, Gilles; the Paris Biota Team (2019). "Glow in the dark: Use of synchrotron μXRF trace elemental mapping and multispectral macro-imaging on fossils from the Paris Biota (Bear Lake County, Idaho, USA)". Geobios54: 71–79. doi:10.1016/j.geobios.2019.04.008. Bibcode: 2019Geobi..54...71B.
↑Brayard, Arnaud; Fara, Emmanuel; Escarguel, Gilles (2019). "Foreword for the thematic issue "The Paris Biota (Bear Lake County, Idaho, USA): an exceptional window on the Early Triassic marine life"". Geobios54: 1–3. doi:10.1016/j.geobios.2019.04.009. Bibcode: 2019Geobi..54....1B.
↑Dai, Xu; Davies, Joshua H.F.L.; Yuan, Zhiwei; Brayard, Arnaud; Ovtcharova, Maria; Xu, Guanghui; Liu, Xiaokang; Smith, Christopher P.A. et al. (2023). "A Mesozoic fossil lagerstätte from 250.8 million years ago shows a modern-type marine ecosystem". Science379 (6632): 567–572. doi:10.1126/science.adf1622. PMID36758082. Bibcode: 2023Sci...379..567D.
↑Botting, Joseph P.; Brayard, Arnaud; the Paris Biota Team (2019). "A late-surviving Triassic protomonaxonid sponge from the Paris Biota (Bear Lake County, Idaho, USA)". Geobios54: 5–11. doi:10.1016/j.geobios.2019.04.006. Bibcode: 2019Geobi..54....5B.
↑Doguzhaeva, Larisa A.; Brayard, Arnaud; Goudemand, Nicolas; Krumenacker, L. J.; Jenks, James F.; Bylund, Kevin G.; Fara, Emmanuel; Olivier, Nicolas et al. (2018). "An Early Triassic gladius associated with soft tissue remains from Idaho, USA—a squid-like coleoid cephalopod at the onset of Mesozoic Era". Acta Palaeontologica Polonica63 (2): 341–355. doi:10.4202/app.00393.2017.
↑Saucède, Thomas; Vennin, Emanuelle; Fara, Emmanuel; Olivier, Nicolas; the Paris Biota Team (2019). "A new holocrinid (Articulata) from the Paris Biota (Bear Lake County, Idaho, USA) highlights the high diversity of Early Triassic crinoids". Geobios54: 45–53. doi:10.1016/j.geobios.2019.04.003. Bibcode: 2019Geobi..54...45S.
↑Thuy, Ben; Escarguel, Gilles; the Paris Biota Team (2019). "A new brittle star (Ophiuroidea: Ophiodermatina) from the Early Triassic Paris Biota (Bear Lake County, Idaho, USA)". Geobios54: 55–61. doi:10.1016/j.geobios.2019.04.004. Bibcode: 2019Geobi..54...55T.
