The environment also became ... These familiar marine arthropods first arose about 545 million years ago in the early Cambrian and thrived throughout the world's oceans until they were wiped ...

and this means that they need to have fossilizable parts and to be buried in an environment that will not destroy them. It has long been suspected that the sparseness of the pre-Cambrian fossil ...

Scientists Stunned to Unearth 500-Million-Yr-Old 3D Cambrian Trilobites Fossils in Best Preserved Condition in Volcanic Ash ...