Trilobite fossils. Rock containing a number of trilobite fossils (Ellipsocephalus hoffi) from the middle Cambrian period (about 515 million years ago). Trilobites are extinct hardshelled, segmented arthropods that lived in the Earths ancient seas. They are considered one of Earths earliest, complex lifeforms and are one of the most wellknown creatures of the Palaeozoic Era. Trilobites existed between the Cambrian and Permian periods around 542250 million years ago, and were mainly bottomfeeding, scavengers.
