Stratigraphically controlled collections from upper Anisian (middle Middle Triassic) strata at Fossil Hill in the Humboldt Range, show 1) that nearly a dozen successive ammonite faunas are present, and 2) that many of the previously described species are variants of conspecific morphologically variable populations. In this advance summary the taxonomic revision and stratigraphic distribution of 37 species, which incorporate 92 of the species recorded from these strata by J. P. Smith, is presented in tabular form.

You do not currently have access to this article.