Burgess Shale fossils
Mud in what is now British Columbia buries a Cambrian sea-floor community about 508 million years ago, preserving soft bodies of early arthropods and chordates in rare detail.
The story
The Burgess Shale is a rock formation high in the Canadian Rockies of British Columbia that holds one of the richest fossil records of early animals. About 508 million years ago, underwater mudslides buried a sea-floor community in oxygen-poor mud. That preserved not only shells but soft bodies: guts, eyes, limbs and gills in thin films of carbon. Charles Doolittle Walcott, head of the Smithsonian Institution, found the site in 1909 near Field, British Columbia, and spent several seasons there, shipping home about 65,000 specimens.
Few places show so clearly what the Cambrian explosion produced. The fossils include the spiny Hallucigenia, the five-eyed Opabinia, the giant predator Anomalocaris, and Pikaia, an early relative of the chordates, the group that includes vertebrates. In the 1970s Harry Whittington, Derek Briggs and Simon Conway Morris reexamined the collection and found many creatures that fit no living group easily; later work placed most of them as early relatives of living arthropods, worms and others. Stephen Jay Gould's 1989 book Wonderful Life brought the debate to a wide audience. The site is part of a UNESCO World Heritage Site, listed in 1980.
Why it mattered
- Soft-bodied preservation gave scientists a window into whole Cambrian ecosystems, not only shelled animals.
- The fossils helped show how fast and varied early animal body plans were after the Cambrian explosion.
- Debates over its odd creatures reshaped how paleontologists classify early animals and think about evolution's pace.
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