Celebrating 100 Years
Charles Doolittle Walcott and the Discovery
of the Burgess Shale (1909)
The Smithsonian’s National Museum of Natural History houses one of the largest collections of one of the most important animal fossil finds in the world. These are not, as you might expect, dinosaur fossils. Surprisingly, you’ll find them in the invertebrate collections—the home of soft-bodied creatures, those that are hardly ever fossilized: the strange, rare, and exquisitely preserved sea-dwelling organisms from the Burgess Shale. These Cambrian age fossils, 505 million years old, were discovered one hundred years ago by the then head of the Smithsonian. Walcott collected some 65,000 specimens from the Burgess Shale. For the past century scientists have continued to study these amazing fossils, opening new windows on the complex and fascinating history of life on Earth. The Museum today has two displays about the Burgess Shale: an older one at the front of the Dinosaur Hall and a new, improved one in the Sant Ocean Hall.
Paleontologist Charles Doolittle Walcott (1850-1927) was appointed the fourth Secretary of the Smithsonian in January 1907, after serving as director of the U.S. Geological Survey. His research on North American Cambrian fossils took him to sites throughout the United States and Canada. In 1909, while collecting in the Canadian Rockies, he discovered the first fossils of an enormous trove of rare, carbonized, soft-bodied fauna from the Cambrian Period. He dubbed the fossils the Burgess Shale after nearby Mount Burgess. The find was so extensive, and the creatures so foreign and new to science, that Walcott returned to the field for the next five summers straight, and then made additional periodic trips up until 1924.
Because they revealed the range and diversity of life in the ancient seas, these exquisite and unusual soft-bodied fauna have come to be recognized as one of the most important geologic discoveries of the twentieth century. These fossils have served as the foundation for the study of the Cambrian Period in western North America.
The Burgess Shale Fauna
Although the fossils are located high up in the Canadian Rockies today, 505 million years ago the area was covered by the sea. The Burgess Shale animals were preserved in a series of mudslides that instantly buried their thriving late Cambrian reef community. The amazing range of fossilized organisms that Walcott and his colleagues discovered at the Burgess Shale give us one of the best picture we have of what is known as the Cambrian Explosion—the burst of diversification and proliferation of animals that gave rise to the lineages of life as we know it today. In the Burgess Shale were found the first examples we have of trilobites, brachiopods, echinoderms, and others, including curious oddities that come from extinct lines.
Discovery of the Burgess Shale
Walcott never recorded the circumstances of the discovery of the Burgess Shale. Many competing accounts have developed over time. The most popular has Walcott traveling on horseback across a scree slope (a slope of loose rock debris). He dismounted to remove a large rock from the trail, but before tossing it aside, he tapped it with his rock hammer to reveal a strange new fossil animal.
Ellis Yochelson, Walcott’s biographer, came across another account, written in 1955 by Walcott’s daughter Helen Stevens Walcott. Walcott typically brought his entire family—his wife Helena and their four children—out into the field with him each summer. Helen credits her mother Helena with the discovery of the Burgess Shale:
Father and Mother were returning to camp one day, by way of Burgess Pass. Father wanted to see an outcrop at the base of the cliffs on Mt. Wapta, so mother waited on the trail while father made the steep climb up the scree. She began to split open the shale by the side of the trail, and by the time father returned she had several very remarkable fossils.
Regardless of who made the find, the discovery revealed, in the words of evolutionary biologist Stephen Jay Gould, “the world’s most important animal fossils.”
Since Walcott’s 1909 discovery, similar fossils have been found in Australia, China, Greenland, Siberia, Spain, and the United States. These new findings have allowed paleontologists to examine more thoroughly the accuracy of the Burgess Shale classifications, as they consider their unique and shared characteristics.
Among these wonderfully strange sea creatures, perhaps the most famous is Hallucigenia. When discovered, it was thought that the animal walked on spiny stilts with tentacles along its back that served as feeding aids. It was impossible to determine which end was the head and which the tail. Recently, scientists in China discovered much better preserved specimens closely related to Hallucigenia. These new specimens revealed a second set of tentacles paired with the first, each tipped with a set of claws. Paleontologists had been looking at Hallucigenia upside down! It is now understood that the “tentacles” of Hallucigenia are pairs of walking legs and that its spiny back protected it from predators. This is a perfect example of how challenging it is for paleontologists to infer the correct anatomy of animals that have no comparative modern forms. Similar challenges arose when paleontologists first began describing dinosaurs.
As part of his geologic research, Walcott photographed topographies for documentary purposes. He often took panoramic photographs of sweeping mountain vistas—which were both aesthetically pleasing and scientifically valuable. In the more than fifteen years that Walcott traveled to the Canadian Rockies, he took over 80 large panoramic views and close to 600 smaller panoramic views; the smaller images were typically 5” x 20” in size, while the larger ones were usually 8’’ high and ranged up to 9 feet in length! The Smithsonian Institution owns the majority of Walcott’s photographs, including cellulose nitrate negatives, glass plate negatives, and original prints. His photographs convey the majesty of Canada’s mountains while demonstrating both early photographic methods and how photography is used in scientific discovery.
The Burgess Shale after Walcott
It was not until the late 1960s—almost forty years after Walcott’s death—that paleontologists began to reconsider Walcott’s Burgess Shale classifications. Harry Whittington of the University of Cambridge and a group of colleagues, using mainly Walcott’s Smithsonian collection of 65,000 fossils, made a series of remarkable discoveries: several of the fossil animals had been erroneously classified as having modern affinities. This was the first challenge to Walcott’s assumption that all Cambrian animals belonged to groups today. Whittington found that while the Cambrian explosion did produce an abundance of diverse life forms that led to most of the animal forms known today, some animals that might have deserved their own phylum actually disappeared during this period. Whittington’s work inspired a renewed intense interest among scientists in the Cambrian Explosion.
At the Smithsonian, paleontologist Douglas H. Erwin, one of the world’s foremost authorities on mass extinctions, continues to study the Burgess Shale and the Cambrian explosion. His books on the subject include The Fossils of the Burgess Shale (co-authored, 1995) and EXTINCTION: How Life on Earth Nearly Died 250 Million Years Ago (2006), and the forthcoming The Cambrian Explosion: The Construction of Animal Biodiversity (co-authored, 2012), which focuses on understnading the mechanisms driving evolutionary innovation. As Erwin explains, “The Early Cambrian was a time of rapid overturn in biodiversity, with high rates of extinction and origination. The disappearance of so many distinctive lineages ... suggests that something different happened.”
The Burgess Shale remains today a highly remarkable fossil locality known both for its diversity and quality of preservation of life forms. In 1981, UNESCO recognized the significance of the Burgess Shale by naming it a World Heritage Site.
Visit the home page of the Burgess Shale in the NMNH’s Department of Paleobiology.
The Burgess Shale Geoscience Foundation runs guided hikes through the Walcott Quarry.
Read “Burgess Shale Weird Wonders,” a 2009 Smithsonian Magazine story.
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