In 1909, Charles D. Walcott of the Smithsonian Institution discovered the first Burgess Shale fossil while hiking in the Canadian Rockies. By the time of his death in 1927, Walcott discovered more than 65,000 fossils in the shale. Despite dedicating years to the task, Walcott did not correctly categorize most of his findings. In the 1960s, Harry Whitington, Simon Conway Morris and Derek Briggs redefined the Burgess Shale fossil record. Their work helped the broader scientific community understand the unique quantity and variety of fossils in the Burgess Shale.
505 million years ago, the North America continental plate was located near the equator. At this time, all life was in the oceans. The land was devoid of any plant life, making it prone to erosion and mudslides. One of these mudslides buried and preserved the Burgess Shale creatures. The continental crust lifted over the course of millions of years due to the collision of the Pacific Plate and the North American Plate.
Arthropods, invertebrates with exoskeletons and a segmented bodies, make up the most common phylum found at Burgess Shale. It includes a large number of trilobites. The trilobite was a class of arthropods that yielded over 20,000 separate species, which makes it one of the most diverse classes of organisms to have inhabited the planet. The Marella splendens is the most common creature found in the Burgess shale. More than 25,000 specimens of that species have been found. The small arthropod is believed to have been a scavenger on the ocean floor.
The shale preserved soft-bodied creatures in great detail. Though half as common as arthropod, sponges represent the second most common fossil found there. The Ottoia was a burrowing priapulid worm that grasped prey with a proboscis, and could reach a length of 8 cm. Hallucigenia were strange spiked and tentacled creatures. Though they resembled worms, they were probably more closely related to arthropods.
Many fossils of colonies of unicellular creatures also turn up in the shale. Algae fossils are the most common, most notably Morania confluens. Cyanobacteria, one of Earth's first life forms, created structures made out of sediment called stromatolites. Cyanobacteria are thought to be the first life forms to use photosynthesis.