The Burgess Shale: Earth's Most Important Fossil Site
The Burgess Shale: Earth's Most Important Fossil Site
Hidden in the Canadian Rockies of British Columbia lies a thin band of 508-million-year-old mudstone that has revolutionized our understanding of early animal life. The Burgess Shale is not just a fossil site — it is a window into the Cambrian Explosion, preserving the soft tissues of organisms that would otherwise have vanished without a trace.
Discovery
In 1909, American paleontologist Charles Doolittle Walcott was riding along a mountain trail near Field, British Columbia, when his horse stumbled on a slab of shale. Split open, it revealed exquisitely preserved fossils of creatures unlike anything in the modern world. Walcott had stumbled upon one of the greatest scientific discoveries of the 20th century.
Over the following years, Walcott excavated tens of thousands of specimens from what he named the Burgess Shale. He shipped them to the Smithsonian Institution, where many sat in drawers for decades before their true significance was recognized.
Why It Matters
Most fossil sites preserve only hard parts — bones, shells, exoskeletons. The Burgess Shale is extraordinary because it preserves soft tissues in remarkable detail: guts, appendages, eyes, gills, neural structures, and even the contents of digestive tracts. This preservation occurred because organisms were rapidly buried in fine-grained mud under anoxic (oxygen-free) conditions on the edge of a submarine cliff (the Cathedral Escarpment), preventing decomposition.
This level of preservation reveals the full diversity of Cambrian marine life — not just the organisms with hard shells, but the entire ecosystem, including the many soft-bodied creatures that are invisible in typical fossil deposits.
Famous Burgess Shale Organisms
Anomalocaris: The apex predator of Cambrian seas. Up to a meter long, with large compound eyes and a pair of grasping appendages flanking a circular mouth. It was one of the largest animals of its time.
Hallucigenia: A worm-like creature with seven pairs of spines on its back and seven pairs of tentacle-like legs. When first described, it was so bizarre that scientists reconstructed it upside down and backwards.
Opabinia: A soft-bodied predator with five eyes on stalks and a flexible, trunk-like proboscis ending in a claw. Its description at a 1972 scientific conference reportedly caused the audience to burst into laughter — nobody believed such an animal could exist.
Pikaia: A small, leaf-shaped creature now considered one of the earliest known chordates — the phylum that includes all vertebrates. Its presence in the Burgess Shale suggests our own distant ancestors swam in Cambrian seas.
Wiwaxia: An armored, slug-like organism covered in scale-like plates and spines. Its exact classification remains debated — it may be related to mollusks, annelids, or represent its own extinct lineage.
Marrella: The most common Burgess Shale fossil, a small arthropod with elaborate head spines. Despite its abundance, it does not closely resemble any modern arthropod group.
Scientific Revolution
In the 1970s and 1980s, a team led by Harry Whittington, Derek Briggs, and Simon Conway Morris re-examined Walcott's Burgess Shale collections with modern techniques. Their findings, popularized by Stephen Jay Gould in his 1989 book Wonderful Life, revealed that the Cambrian contained far more diverse body plans than the modern world — many of which left no descendants.
This challenged the traditional view of evolution as a gradual, cone-shaped diversification. Instead, the Cambrian appeared to have produced a wild profusion of body plans, many of which were subsequently pruned by extinction. The debate over whether Cambrian diversity truly exceeded modern diversity continues, but the Burgess Shale remains central to our understanding of early animal evolution.
UNESCO World Heritage Site
The Burgess Shale was designated a UNESCO World Heritage Site in 1981 (as part of the Canadian Rocky Mountain Parks). Collecting is strictly prohibited, and access to the fossil-bearing outcrops requires guided tours led by Parks Canada staff.
Additional Burgess Shale-type deposits have been discovered worldwide, including the Chengjiang Biota in China (slightly older, at 518 Mya) and the Emu Bay Shale in Australia, expanding our picture of Cambrian life.
Explore Burgess Shale Fossils
The Eon Codex includes several specimens from the Burgess Shale. You can explore them in our specimen collection or learn more about the Cambrian Period and the Paleozoic Era.