Trilobites from the Redwall Limestone (Mississippian) of Arizona

ABSTRACT Trilobites from the Lower Mississippian (late Tournaisian) Redwall Limestone of Arizona are rare. Four identifiable specimens were recovered and studied. These specimens, in conjunction with recorded stratigraphic distributions of lost Redwall trilobites, allows for the assemblage of a range chart. Identifiable trilobite species include: Aprathia sp., Phillipsia peroccidens (Hall and Whitfield, 1877), Cummingella? sp., and Cummingella sp. The Redwall trilobites in this small collection exhibit a much closer taxonomic affinity to the late Tournaisian forms known from Europe than they do to species from strata of similar age in the eastern, central, and southern United States. This suggests that during the late Tournaisian the inferred geographic barrier known as the Transcontinental Arch prominently separated the Redwall depositional location from that of the central and eastern United States. This barrier appears to have contributed to the endemism of trilobites of the eastern United States.