The Paris biota is an exceptionally diverse Early Triassic (approximately 249 million years ago) 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. 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.
Age
The Paris biota was found in layers dating back to the earliest Spathian, a substage of the Olenekian stage of the Early Triassic epoch. The biostratigraphy is constrained by the presence of the ammonoids Tirolites and Bajarunia, and conodonts. The Tirolites/Columbites beds are dated with 248.853±0.086 Ma. 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.
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.
Assemblage The Spathian aged Paris biota is one of the earliest diverse fossil assemblages from the post-extinction interval, about 3 million years 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) 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. 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 leptomitid protomonaxonid sponges, a group that is otherwise known from the early Paleozoic era (e.g. from the Cambrian Burgess 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. The study of some fossils could be improved using synchrotron μXRF imaging.
Most organisms of the Paris biota were described in a thematic issue of the journal Geobios in 2019, but new taxa were also subsequently described.
In 2023, another diverse post-extinction biota was presented from South China, the Dienerian aged Guiyang biota, which includes fossils belonging to twelve classes and 19 orders. The Early Triassic is generally considered as an environmentally unstable and diversity-poor interval, 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):
Sponges
Porifera of the Paris biota Taxon / Genus Species NotesPseudoleptomitusP. advenusA leptomitid protomonaxonid sponge similar to Leptomitus. This group was previously only known from the Cambrian and Ordovician periods
Brachiopods
Brachiopoda of the Paris biota Taxon / Genus Species NotesBrachiopodaGen. et sp. indet.An epizoan species closely associated with the spongesLingulariaL. borealisA lingulidRhynchonellataGen. et sp. indet.A brachiopod
Mollusks
Mollusca of the Paris biota Taxon / Genus Species NotesAlbanitesA. americanusAn ammonoid cephalopodAvichlamys?A.? csopakensis?A pectinid bivalveBajaruniaB. cf. pilataAn ammonoid cephalopod typical of the earliest Spathian substageBelemnoideaGen. et sp. indet.Arm hooks of a belemnoidCariboucerasC. slugenseAn endemic ammonoid cephalopodColumbitesC. parisianusAn ammonoid cephalopodCoscaitesC. crassusAn ammonoid cephalopodCritendeniaC. kummeliA bivalveCrittendenia sp.A claraiid bivalveEumorphotisE. cf. ericiusA heteropectinid bivalveE. multiformis?A heteropectinid bivalveEumorphotis sp.A heteropectinid bivalveHedenstroemiidaeGen. et sp. indet.An ammonoid cephalopodIdahoteuthisI. parisianaA gladius-bearing coleoid cephalopodLeptochondriaL. curtocardinalisA hunanopectinid bivalveL. nuetzeli?A hunanopectinid bivalveL. occidaneaA hunanopectinid bivalveL. virgalensis?A hunanopectinid bivalveLeptochondria sp.A hunanopectinid bivalvePhaedrysmocheilusP. idahoensisA nautiloid cephalopodPleuronectitesP. meekiA pectinid bivalveScythentoliumScythentolium sp.A entoliid bivalveTirolitesT. hartiAn ammonoid cephalopod typical of the earliest Spathian substageT. aff. cassianusAn ammonoid cephalopod typical for the earliest Spathian substageTrematocerasTrematoceras sp.An orthoconic nautiloid cephalopod
Arthropods
Arthropoda of the Paris biota Taxon / Genus Species NotesAegerAeger sp.An aegerid prawnAnisaegerA. longirostrus An aegerid prawnAnkitokazocarisA. triassicaA thylacocephalanCarideaGen. et sp. indet. A shrimpHoplocaridaGen. et sp. indet. A malacostracan crustaceanLigulacarisL. parisianaA thylacocephalanLimulidae?Gen. et sp. indet. A xiphosuran chelicerateLitogasterL. turnbullensis? A glypheid pleocyemate crustaceanLitogaster sp.A glypheid pleocyemate crustaceanPenaeoideaGen. et sp. indet. A prawnPemphixP. krumenackeriA glypheid pleocyemate crustaceanThylacocephalaGen. et sp. indet. A thylacocephalanTriassosculdaT. ahyongiA mantis shrimp
Echinoderms
Echinodermata of the Paris biota Taxon / Genus Species NotesHolocrinusHolocrinus nov. sp.A sea lilyShoshonuraS. brayardiAn ophiacanthid brittle star
Chordates
Chordata of the Paris biota Taxon / Genus Species NotesActinistiaGen. et sp. indet.Coelacanth remainsBobasatraniaBobasatrania sp.A bobasatraniiform ray-finned fish. Complete specimensHybodontiformesGen. et sp. indet. AA slab with several hybodontiform chondrichthyan teeth showing a heterodont durophagous dentitionGen. et sp. indet. BA single hybodontiform toothOsteichthyesGen. et sp. indet.Tooth plateVertebrataindet.coprolites referrable to large vertebrate producers
Algae
Algae of the Paris biota Taxon / Genus Species NotesAlgaeGen. et ap. indet.Filamental algae and other algaeDasycladalesGen. et ap. indet.An unicellular green algaeRhodophytaGen. et ap. indet.A red algae
See also
Triassic Lagerstätten Paleontology in Idaho Paleontology in Nevada
References