A trilobite pygidium, likely referable to the genus Bonnima, is the first evidence of a member of the Corynexochida reported from the Lower Cambrian (Dyeran Stage) Chambless Limestone of the southern Marble Mountains in the Mojave Desert of California. This specimen represents the first occurrence of the family Dorypygidae in the cratonic facies of the Lower Cambrian in the California-western Nevada region, as all of the few previous reports of the family (mostly Bonnia) have been from much thicker, more distal open-shelf deposits far to the northwest in the White-Inyo—Esmeralda County region of California and Nevada. Although still relatively rare, the occurrence of Dorypygidae across a range of environments biofacies realms in this area is typical of their distribution in other regions.
