Paris Biota (Triassic of the United States)

Where: Idaho (42.2° N, 111.5° W: paleocoordinates 11.7° N, 35.4° W)

• coordinate estimated from map

• local area-level geographic resolution

When: Lower Shale Member, Spathian (251.3 - 247.2 Ma)

• The exposures dip gently northward and their combined thickness reaches ~20 m. They are located below the Spathian Middle Limestone unit and overlie the Smithian Lower Limestone unit. However, the contact with the Lower Limestone unit is not visible in this area. The occurrence of the ammonoid species Tirolites harti indicates an early Spathian age for the Middle Limestone unit. This unit is coeval or slightly older than the Tirolites/Columbites beds of South China, which yield a radiometric age of ~250.55 ± 0.4 Ma. Abundant Tirolites specimens are also reported here for the first time from the upper part of the underlying Lower Shale unit where the Paris Biota occurs; unfortunately, their compressed preservation prevents a firm species assignment. However, the genus determination is easy and robust enough to confirm an earliest Spathian age for this biota as this genus is found worldwide in this time interval only. Tirolites specimens are found throughout the four studied exposures of the upper part of the Lower Shale unit, confirming their earliest Spathian age.

• group of beds-level stratigraphic resolution

Environment/lithology: transition zone or lower shoreface; lithified, silty mudstone and lithified marl

• The presence of erosion surfaces as well as associated HCS structures alternating with thin-bedded micritic mudstones and marls, argue for deposition in a distal upper offshore environment on a very flat platform. HCS, cogenetic wave ripples, silty laminae and sponge spicule accumulations are interpreted to reflect storm-wave action along a shelf profile.
• Sedimentary deposits of fossiliferous horizons show alternating cm-thick mudstones with silty laminae and marls

Size classes: macrofossils, mesofossils

Preservation: mold/impression

Collection methods: Repository: Université de Bourgogne, Géologie Dijon, France

Primary reference: A. Brayard, L. J. Krumenacker, J. P. Botting, J. F. Jenks, K. G. Bylund, E. Fara, E. Vennin, N. Olivier, N. Goudemand, T. Saucède, S. Charbonnier, C. Romano, L. Doguzhaeva, B. Thuy, M. Hautmann, D. A. Stephen, C. Thomazo and G. Escarguel. 2017. Unexpected Early Triassic marine ecosystem and the rise of the Modern evolutionary fauna. Science Advances 3:e1602159 [M. Clapham/M. Clapham]more details

Purpose of describing collection: general faunal/floral analysis

PaleoDB collection 202145: authorized by Valerie Syverson, entered by Valerie Syverson on 27.06.2019, edited by Matthew Clapham

Creative Commons license: CC BY (attribution)

Taxonomic list

Malacostraca
 Decapoda -
Penaeoidea indet. Rafinesque 1815 decapod
Caridea indet. Dana 1852 shrimp
 Decapoda - Litogastroidae
Litogaster sp. Von Meyer 1847 decapod
Thylacocephala
 Concavicarida - Microcarididae
Parisicaris triassica n. gen. n. sp.3
Parisicaris triassica n. gen. n. sp.3 Charbonnier 2019
 Concavicarida - Concavicarididae
Ligulacaris parisiana n. gen. n. sp.3
Ligulacaris parisiana n. gen. n. sp.3 Charbonnier 2019
Lingulata
 Lingulida - Disciniidae
Orbiculoidea indet. d'Orbigny 1847
 Lingulida - Lingulidae
Lingularia borealis Bittner 1899
Bivalvia
 Pectinida - Entoliidae
Scythentolium sp. Allasinaz 1972 scallop
 Pectinida - Pectinoidae
? Pleuronectites sp. Schlotheim 1820 scallop
 Pectinida - Hunanopectinidae
Leptochondria curtocardinalis Hall and Whitfield 1877 scallop
 Pectinida - Buchiidae
Eobuchia sp. Wasmer and Hautmann 2012 scallop
 Carditida - Astartidae
Astartella sp. Hall 1858 clam
Cephalopoda
 Orthocerida - Orthoceratidae
Trematoceras sp.2 Eichwald 1851
 Coleoidea -
Coleoidea indet. Bather 1888
 Ceratitida - Albanitidae
Albanites americanus n. sp.2 Brayard et al. 2019 ceratite
 Ceratitida - Tirolitidae
Tirolites harti2 Smith 1932 ceratite
 Ceratitida -
Bajarunia cf. pilata2 Hyatt and Smith 1905 ceratite
Chondrichthyes
 Euselachii -
Hybodontiformes "indet. B"4 Patterson 1966 elasmobranch
Hybodontiformes "indet. A"4 Patterson 1966 elasmobranch
Osteichthyes
 Actinopterygii -
Actinopterygii indet. Cope 1887 ray-finned fish
Ophiuroidea
 Ophiurida -
Shoshonura brayardi n. gen. n. sp.6
Shoshonura brayardi n. gen. n. sp.6 Thuy 2019 brittle star
Crinoidea
 Holocrinida -
Holocrinus sp.5 Wachsmuth and Springer 1886 Sea lily
Demospongea
 Protomonaxonida - Leptomitidae
Pseudoleptomitus advenus n. gen. n. sp.1
Pseudoleptomitus advenus n. gen. n. sp.1 Botting 2019 demosponge