A new Cambrian (Jiangshanian, Sunwaptan) trilobite fauna from Oklahoma and its biostratigraphic significance.

A newly discovered trilobite fauna from the Cambrian Honey Creek Formation marks a distinct interval that follows an extinction event. Dominated by the genus Monocheilus in association with Ptychaspis, it resembles faunas from Alberta, Canada, and the Upper Mississippi Valley region of the United States. Ptychaspis bullasa Lochman and Hu, 1959 is a species that has been reported widely in North America. However, restudy of various museum collections shows that the various occurrences record a set of more narrowly distributed species. The pattern of distribution is similar to groups of modern “pseudocryptic species” identified by a combination of genetic and anatomical data.