Late Early Triassic foraminifers from possible dysaerobic to anaerobic paleoenvironments of the Thaynes Formation, Southeast Idaho

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Abstract
An abundant and diverse foraminiferal assemblages is present in the late Early Triassic Thaynes Formation in the Bear Lake area of southeast Idaho. More than 2,000 fairly well-preserved specimens were recovered from the basinal facies of the Cordilleran miogeosyncline, which consists of alternating homogenous and laminated green mudstones interpreted to have been deposited under dysaerobic (1.0-0.1 ml O2/L) to possibly anaerobic (<0.1 ml O2/L) conditions. Most of the species have compressed morphologies that have been interpreted to be characteristics of foraminifers from anaerobic environments. Two of the 17 species reported, Verneuilinoides edwardi Schroeder, 1968, and Lingulina triangulata Schell and Clark, 1960, were originally described from Early Triassic strata in the region. Pseudonodosaria simplex Heath and Apthorpe, 1986, was described from the Middle Triassic of Australia. Two others, Ammobaulites sp. cf. A. directa Scherp, 1962, and Astacolus sp. cf. Lenticulina (A.) initialis Crespin, 1958, have distinct affinities with Permian species. The species of Ammodiscus, Aaptotoichus, Astacolus?, Nodosaria [tereta], Lenticulina?, and Lingulina? are left in open nomenclature at this time, but we describe three new species: Evolutinella idahoensis, Textulariopsis taylori, and Palmula triassica. [Also described is Lingulina triangulata].