Perfect Enrolled Phacops rana crassituberculata Trilobite

An absolutely exquisite and perfect example of this increasingly hard to find species. A must have species for the collector of American or Mid-Western trilobites. Note the light chocolate color, pustulate cephalon and lenses in the eyes. This is a very fine, 3-D enrolled examples of a trilobite seldom seen. Enrollment was a defensive response to predators, and is the way crassituberculata trilobites are most frequently found. Some prefer to use the genus Eldredgeops, named after Nils Eldredge, whose study of Phacops trilobites led him to hypothesis that modifications to the arrangement of the trilobite’s eye lenses proceeded in rapid change followed by stasis over millions of years during the Devonian. Eldredge's interpretation of the Phacops fossil record was that the aftermaths of the lens changes, but not the rapidly occurring evolutionary process, were fossilised. This and other data led Gould and Eldridge to publish the initial paper explaining punctuated equilibrium in 1971.