An olenellid trilobite cephalon (head shield) from the lower Cambrian Mule Spring Limestone, Esmeralda County, Nevada. Called scientifically Olenellus (Paedeumias) puertoblancoensis.

One of the last olenellid trilobites to exist; the specimen came from a stratigraphic interval in the Mule Spring Limestone immediately above which (in younger rocks) all olenellid trilobites permanently disappear from the geologic record during the latest early Cambrian Period some 510 million years ago. Photograph courtesy a specific web page.