What is the Burgess Shale?

The Burgess shale is a collection of extremely well-preserved fossils from the Cambrian period, from about 550 to 480 million years ago. It is located near Burgess Pass, high up in the Canadian Rockies in the province of British Columbia. Although discovered in 1909, it was not until the 1980s that the fossils were rediscovered and their true significance determined. The black shale in which these organisms are preserved, from which the Burgess shale gets its name, has an extremely fine grain size, allowing for high-quality fossils and even the fossilization of organisms lacking hard shells. The Burgess shale is famous for what it has told us about the Cambrian explosion, a period of time in the early Cambrian when all major phyla of life emerged in a paleontologically negligible amount of time, only a couple tens of millions of years.

Many of the finds were arthropods, early ancestors of modern-day bugs. Others come from more exotic phyla such as Hallucigenia sparsa, which is a member of the phylum Onychophora, which includes modern-day velvet worms. Hallucigenia, named after its bizarre, hallucinatory appearance, is a rod-like creature with various spikes protruding perpendicular to its axis in various directions. Opabinia is a difficult-to-classify organism with five eyes and a hose-like snout capped by a mini-mouth or grappler with teeth, an appendage that no other known animal has.

Trilobites were found in large quantities within the Burgess shale, as well as Nectocaris, an unusual streamlined animal that has some characteristics of vertebrates and others of arthropods, making it a nightmare for biological taxonomists. In general, the Burgess shale is responsible for producing the majority of difficult-to-classify specimens in the early fossil record.

Perhaps the most famous of Burgess shale organisms is Anomalocaris, the world's first apex predator, whose name means "anomalous shrimp", which grew to a huge 2 m in length, truly large for the time. It swam through the water using flexible lobes all up and down its side, and used two grapplers located near its mouth to grab prey and shove it in. Its bizarre mouth resembles a slice of pineapple, with sharp barbs all around the edges. Anomalocaris also had some of the most developed eyes for any organism existing at the time.

Today, the task still continues of excavating the Burgess shale and finding the biological wonders it has to offer. Some of the organisms contained therein are so rare or fossil-unfriendly that only single specimens exist, limiting our knowledge about the species. Further investigation could turn up new surprises for biology that we can now only speculate about.