Episode 48: The Burgess Shale
The Burgess Shale is probably the world’s most famous lagerstätte (site of special preservation). Discovered in 1909 on Mt. Stephen, in the Canadian Rockies of British Colombia, Canada, this locality provided an early representation of the true biodiversity of the Cambrian Period. For decades, discoveries from this site have helped palaeontologists better understand the ‘Cambrian Explosion’ and the origins of modern lineages. Since that time, many more early lagerstätten have been discovered, so we asked Prof. Simon Conway Morris, from the University of Cambridge, if this well-studied locality still holds its relevance to modern palaeontology.
Podcast: Download (Duration: 44:17 — 60.8MB)
Location of the Burgess Shale: On Mt. Stephen, close to the town Field, in the Canadian Rockies, British Colombia, Canada. The locality is in the Yoho National Park and is protected by Parks Canada.
The Burgess Shale is part of the Stephen Formation, located to the West of the Cathedral Escarpment. In the Middle Cambrian (approximately 508 million years ago), the Cathedral Escarpment was a large underwater cliff down which density flows (underwater sediment avalanches) often cascaded. The Stephen Formation was formed by the collection of these density flows at the bottom of this cliff. Image credit: Alberta Geological Survey.
This lagerstätte was discovered by Charles Doolittle Walcott, a Palaeontologist at the Smithsonian Institution. Legend has it that Mrs Walcott’s horse stumbled on a rock which, when broken, contained remarkably preserved fossils.
Charles Walcott excavating at the Burgess Shale locality family members. Image credit: Smithsonian Institute
The same quarry today. It was since named Walcott Quarry in honour of its discoverer. Image credit: Jakob Vinther
Most common in the Burgess Shale is the arthropod Marrella splendens. Marrellomorph arthropods look like naked trilobites, but this is now suggested to be more of a superficial resemblance than any close relationship relative to any other group of arthropods. Image credit: Hannah Caine.
Marrella splendens juxtaposed with a modern arthropod. Image credit: Jakob Vinther
Working alongside Prof. Conway Morris, in their early years at the University of Cambridge, was Prof. Derek Briggs, now of Yale University. Prof. Briggs dealt mainly with the arthropods whilst Prof. Conway Morris handled the annelid worms. Image credit: Jakob Vinther
The annelid worms might sound less spectacular, but in reality are far from it. Canadia spinosa. Image credit: Luke Parry
One of the fossils Prof. Conway Morris is most famous for working on is Pikaia gracilens . This is an early chordate and so can be considered an early relative of any animal with a backbone. Anatomical diagrams and putative cross sections of Pikaia gracilens . (A) Overall lateral view. (B, C) Close ups of the anterior section (B, front and dorsal views; C, lateral view). (D, E) Close ups of the mid anterior and posterior sections (lateral views). DO, dorsal organ (blue); Ne, nerve cord (yellow); No, notochord (green); gut (brown); VBV, ventral blood vessel (red). From Conway Morris & Caron 2012.
In the century since the Burgess Shale was discovered, many more Cambrian lagerstätten have been found, including the Maotianshan Shales from Chengjiang County, China. Image: Maotianshania cyliindrica. Image credit: Dwergenpaartje CC BY-SA 3.0.
Nevertheless, the Burgess Shale continues to produce new discoveries and provides new insights into the Cambrian world. Which is your favourite Burgess Shale organism? Let us know in the comments below! Image credit: Carel Brest van Kempen
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