Dorsal reconstruction of the trilobite, Olenoides serratus, from the Middle Cambrian Burgess Shale of British Columbia. An icon for the Cambrian Period, this common trilobite in the Burgess Shale has been preserved intact with its legs, antennae, and delicate feathery gills. Traces of soft-bodied animal remains in its gut indicate that Olenoides was probably an active predator and scavenger. It ranges in size from 50 to 85 mm.