Diagnostic ammonites and other fossils indicate that much of the Natchez Pass formation in northwestern Nevada is of early Late Triassic (Karnian) age instead of Middle Triassic age as originally dated. Trachyceras, sensu stricto, of early Karnian age occurs in the lower part of the Natchez Pass formation in the East Range and is tentatively identified from corresponding stratigraphic position in the Humboldt Range. The upper part of the formation in the northeastern foothills of the Humboldt Range has yielded large upper Karnian fauna including Paratropites cf. P. sulcatus (Calcara), Spirogmoceras shastense (Smith), Pleuronautilus? alaskensis Kummel, and Septocardia sp., which are described in this paper.

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