Fallotaspidoid trilobite assemblage (Lower Cambrian) from the Esmeralda Basin (western Nevada, U.S.A.): The oldest trilobites from Laurentia

An assemblage of fallotaspidoid trilobites is present in an interval 58 to 126 m thick at the top of the Andrews Mountain Member of the Campito Formation in Esmeralda County, Nevada and adjacent areas of California. This fauna occurs 37 to 40 m below the lowest members of the 'Fallotaspis' Zone making it the oldest trilobite fauna from the Laurentian Cambrian. The trilobite bearing interval is interpreted as a lowstand systems tract with shallow-water arenites containing numerous trace fossils. The rocks above and below this interval are dark coloured siliciclastics deposited as dysoxic subtidal sediments. The trilobites are rare and poorly preserved due to the arenaceous matrix. Two new genera are present, Fritzaspis gen. nov. with new species F. generalis, F. ovalis and F. sp. nov., and Amplifallotaspis keni gen. et sp. nov. The other forms are Repinaella sp. and Profallotaspis? sp. This interval is termed the Fritzaspis Assemblage Zone and correlates with the lower part of the Atdabanian Stage of Siberia.