In what is now Yoho National Park, a submarine landslide is forming, covering the future fossils of the Burgess Shale: specimens of soft-bodied organisms preserved in astonishing detail. These are ancient representatives of all four major groups of arthropods, the dominant animals on Earth: trilobites, crustaceans, chelicerates (such as modern spiders and scorpions), and uniramids (insects). But the Burgess deposit also contains at least a dozen organisms that do not belong to any modern phylum (sponges, coelenterates, annelids, mollusks, arthropods, echinoderms, chordates), each of which could be unique representatives of a new phylum; as well as 20-30 arthropods that cannot be placed in any modern group.
