What’s the Burgess Shale?

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The Burgess shale is a collection of extremely well preserved fossils from the Cambrian period, approximately 550 to 480 million years ago. It is located near Burgess Pass high 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, after which Burgess shale is named, has an extremely fine grain size, which allows for high-quality fossils and even the fossilization of organisms that lack hard shells. Burgess Shale is famous for what he told us about the Cambrian Explosion, a period of time in the Early Cambrian in which all major life phyla emerged in a palaeontologically negligible amount of time, just a couple of tens of millions of years.

Many of the finds were arthropods, the earliest ancestors of modern insects. 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 and hallucinatory appearance, is a rod-like creature with various spikes projecting perpendicular to its axis in various directions. Opabinia is a hard-to-classify organism with five eyes and a tube-like snout covered by a mini-mouth or toothed grappler, an appendage that no other known animal has.

Trilobites have been found in large numbers within the Burgess Shale, as have Nectocaris, an unusual streamlined animal that has some vertebrate and some arthropod characteristics, making it a nightmare for biological taxonomists. In general, Burgess shale is responsible for producing most of the hard-to-classify specimens in the early fossil record.

Perhaps the most famous of Burgess’s shale organisms is Anomalocaris, the world’s first apex predator, whose name means ‘anomalous shrimp’, which grew to a whopping 2m in length, truly large for its time. It swam in the water using flexible lobes up and down its sides, and used two grappling hooks located near its mouth to grab prey and thrust it inside. Its bizarre mouth resembles a slice of pineapple, with sharp points all around it. Anomalocaris also had some of the most highly developed eyes for any organism in existence at the time.

Today, the task of digging into the Burgess Shale and finding the biological wonders it has to offer still continues. Some of the organisms it contains are so rare or hostile to fossils that only single specimens exist, limiting our knowledge of the species. Further investigation could reveal new surprises for biology that we can now only speculate about.

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