Summary of Research
The first geologist to visit the Mt. Stephen Trilobite Beds was R.G. McConnell of the Geological Survey of Canada (GSC), in 1886. He collected a number of trilobites, as well as fossils that he identified as the body of a shrimp, and named Anomalocaris canadensis, or “odd shrimp”. In fact, the fossils were the moulted claws of the giant predator, Anomalocaris, and it took 96 years for scientists to piece together what the ancient animal really looked like.
Collections from the Trilobite Beds had also been made by Canadian Pacific railway workers. Charles Walcott of the Smithsonian Institute, the leading expert on Cambrian-age fossils at that time, heard about their reports of “stone bugs” and first visited the site on Mt. Stephen in July, 1907. He published a comprehensive account of the fossils from that location in 1908.
Walcott discovered the first fossils from the more famous Burgess Shale site along the horse trail near Burgess Pass on Aug 30, 1909. The following season, he located the source of the fossils higher up on Fossil Ridge, and began excavating. The fossils, with their exquisite preservation, were unlike anything he had seen before. He named the site the Burgess Shale, after nearby Mt. Burgess. That specific site is now known as Walcott’s Quarry.
Walcott spent the summers between 1910-1917 excavating the quarry with the help of his family. He collected more than 65,000 specimens that were sent to the Smithsonian Institute in Washington, D.C.. Walcott classified the various fossils within our modern classification system, interpreting the fossils to be ancestors of animals alive today. He carefully documented his specimens with retouched photographs.
The next work to be done on the Walcott quarry site was by Percy Raymond of Harvard. In 1930, he collected from Walcott’s quarry, and then opened up another smaller quarry 20 metres above, which is now referred to as the Raymond Quarry. The two quarries differ somewhat in their fossil assemblages, and the specimens in Raymond’s quarry tend to be a little larger.
The quarries were reopened by the GSC in 1966-67, and fossil collections were made. Many new, unknown specimens were recovered, which instigated a restudy of the Burgess Shale fossils led by Harry Whittington of Cambridge, along with his graduate students, Derek Briggs and Simon Conway-Morris. Walcott’s notes and photos had lain in drawers alongside his fossil specimens for nearly half a century, until 1973, when the Cambridge scientists dusted them off to have another look. Between 1971 and 1985, Whittington et al. published papers describing in great detail most of the soft-bodied fossils. To their surprise, they were unable to classify many of them within our modern classification system, listing them instead as members of unknown phyla, implying that there had been a greater diversity of basic animal forms half a billion years ago than today. Our understanding of evolution was turned on its head!
Recognition of the significance of the Burgess Shale led to its declaration as the 86th UNESCO World Heritage Site in 1981. The fossils were made famous with Stephen J. Gould’s best-selling book, Wonderful Life in 1989. Based on the work of Whittington et al., Gould concluded that “more than half of the major animal groups present in the Cambrian seas are extinct. He attributed this to the effects of contingency (or mass extinction) being more drastic than previously thought. Indeed there have been 5 great periods of extinction in Earth’s history. The one we are most familiar with is the extinction of the dinosaurs at the end of the Cretaceous period, 65 million years ago, that allowed mammals to diversify, ultimately leading to the rise of Man.
One of the world’s leading experts on the fossils today is Dr. Desmond Collins of the Royal Ontario Museum (ROM) in Toronto. Dr. Collins logged his 16th field season working on the Burgess Shale fossils in Yoho National Park last summer. The ROM first collected from the quarries on Fossil Ridge in 1975. They returned in 1981, seeking new localities of the fossils by following the ancient reef front mapped previously. This proved very successful, and more than a dozen new localities were found in a 20 km vicinity of the original Walcott quarry. Since then, the ROM has collected from these new sites, finding a number of new and rare fossil forms.
Continuing work by paleontologists around the world has led to a reinterpretation of some of the previously unclassifiable forms such that they can now be classified in our modern system. However, there are just as many new unclassifiable forms from recent discoveries that have been made, maintaining the case for greater biodiversity in the Cambrian seas than in our modern oceans. Debate on the implications of the Burgess Shale fossils with regard to the evolutionary process rage on, and the saga continues.
Dr. Collins summarizes by saying, “the fossils of the Burgess Shale tell us more about how animal life appeared on Earth than any other fauna in the fossil record. It is thus our most important fossil Lagerstatte, and deserves its World Heritage Site status.”
- Collins, D.H., 1992. Geology and Paleontology of the Mt. Stephen Trilobite Beds and the Burgess Shale in the Stephen Formation, Yoho National Park, British Columbia, SEPM Trip #22 Field Trip Guidebook.
- Collins, D.H., and Stewart, W.D.. The Burgess Shale and Its Environmental Setting Fossil Ridge, Yoho National Park.