Trilobites and the Cambrian Explosion Fossil Record suggests: The Cambrian Explosion likely realized a 10-fold increase in evolutionary adaptation Trilobites are already highly diverse and geographically dispersed when they appear in the fossil record As the most diverse animals of the Paleozoic, the trilobites fossil record has provided a metric to estimate rates of speciation during the Cambrian Explosion Trilobites are the stratigraphy biomarkers for the Cambrian period, making them important in the study of plate tectonics Trilobites appear in the fossil record in the early Cambrian, some 521 million years ago The so called Cambrian Explosion begins at the base of the Paleozoic Era, some 540 million years ago www.trilobites.us Teaching Tools