Posted on: Friday February 16, 2024
Animals today are mindbogglingly diverse, encompassing flies and flamingoes, elephants and earthworms, sharks and snails, and of course, ourselves. It’s hard to even imagine a world before animals, or how such staggering diversity came to be.
My name is Dr. Joe Moysiuk and I am the new Curator of Palaeontology and Geology at the Manitoba Museum. It’s my job to reconstruct ancient worlds through scientific study of the evidence that remains – fossils and rocks – and bring them “back to life” for museum visitors. I’m particularly fascinated by the evolution of major groups of animals and have devoted the past several years to researching fossils from the Burgess Shale, a UNESCO World Heritage Site and one of the world’s most significant palaeontological discoveries.
Famous shale
The Burgess Shale is located high in the mountains of Yoho and Kootenay National Parks in British Columbia. Fossils were discovered by workers during the construction of the Canadian Pacific Railway in the 1880s. Although a few sites were explored by earlier researchers, it wasn’t until 1909 that Charles D. Walcott of the Smithsonian Institution made the famed discovery of a particularly diverse excavation site and provided the name Burgess Shale after the nearby Mount Burgess. Subsequent expeditions by Harvard, the Geological Survey of Canada, and Royal Ontario Museum (ROM) have yielded large research collections that have been scrutinized by countless scientists and popularized in books like Wonderful Life by legendary palaeontologist Stephen J. Gould. Collection and research continues, notably at ROM, my previous institutional home.
The Burgess Shale fossils date back roughly 506 million years, to the Cambrian Period – long before the dinosaurs or even the earliest evidence of large lifeforms on land. At first glance, they are not particularly charismatic; most appear as small, dark stains on dark rocks and are difficult to see without special lighting conditions. Contrary to their modest appearance, these fossils have had an outsized impact on our understanding of the origin and evolution of animals.
Walcott’s quarry today, showing the marks of 100 years of excavation.
Not your ordinary fossils
When I mention the word fossil, dinosaur bones may come to mind. Alternatively, you might recall seeing the shells of molluscs and corals in the Tyndall stone walls of buildings that dot the streets of Winnipeg or other Canadian cities. These sorts of hard, mineralized remains of organisms are resistant to decay, scavenging, and breakage, so they have a decent chance of persisting long enough to become fossilized. The softer parts of organisms, like eyes, digestive tracts, or brains tend to be lost long before they can be buried and preserved from further degradation.
However, there are some fossil deposits that defy these rules, preserving traces of the soft tissues of organisms alongside their mineralized bits. In technical parlance, we call these sites Konservat-Lagerstätten, deriving from an old German mining term for “conservation motherlode.” The Burgess Shale is one such Lagerstätte, and the exceptional quality and quantity of fossil material has made it among the most renowned.
A specimen of Stanleycaris, a smaller relative of the more famous Anomalocaris. This fossil is exceptional even by the standards of the Burgess Shale – the dark matter in the head and extending into the bulbous eyes is the remains of the brain and associated nervous tissues. Photo by Jean-Bernard Caron, © Royal Ontario Museum, used with permission.
A pair of Burgessomedusa phasmiformis, the oldest jellyfish known from the fossil record. These fossils were collected in the 1980s, but the species was only formally described last year. Photo by Jean-Bernard Caron, © Royal Ontario Museum, used with permission.
As you can imagine, soft tissue preservation provides unique insights about past life. For example, we recently uncovered fossilized elements of the nervous system of Stanleycaris hirpex, a distant relative of modern insects, spiders, and crabs, giving us extraordinary direct evidence of the form of the brain in the common ancestor of these disparate animals. We also find representatives of entirely soft bodied groups of organisms, which would never be found in a typical fossil deposit. For example, my colleagues and I recently described the oldest definitive swimming jellyfish.
The reasons behind the exceptional quality of preservation at the Burgess Shale, and other similar sites around the world, remain the subject of research. It’s generally thought that a combination of factors played a role: rapid burial of the organisms in undersea mud flows, low oxygen near the sea floor, and unusual sea water chemistry during this time in Earth’s history. Subsequently, chemical reactions during rock formation reduced the organic remains to carbon-rich traces which were resistant enough to survive for over half a billion years.
Aside from the quality of preservation, the age of the Burgess Shale makes it particularly significant. The Cambrian Period witnessed a spectacular diversification of animals. Essentially all major groups that are with us today can trace their roots back to this time. The Burgess Shale provides a window into life on Earth shortly after this pulse of animal diversification.
Opening new doors to ancient worlds
I started my museum career at a particularly exciting time. Field work at the Burgess Shale had just resulted in the discovery of a brand new Burgess Shale site in the vicinity of Marble Canyon in Kootenay National Park. This site lies a mere 40 km south of Walcott’s quarry, but differs substantially in terms of the fossil species present. For several summers between 2014 and 2022, I joined international crews in exploring the region and excavating several dig sites systematically. Access to the sites is challenging and mostly by helicopter. We would camp in these remote settings for 2-6 weeks at a time, hiking long distances to reach fossil-rich outcrops. The work was hard and physical, but the rewards were truly spectacular. In the early days of exploration, new fossil species tumbled out of broken shale on a near daily basis. Some of these finds have now been formally published, but many still await attention and will be the basis of years of research to come.
Campsite from 2018. Finding a flat area to pitch multiple tents can be challenging in the mountains.
One of several excavation sites developed over the past decade in the vicinity of Marble Canyon, Kootenay National Park.
Using a rock saw to extract fossils from a block of shale.
A fossil of Marrella splendens, showing curving spines on the head, antennae, and numerous feather-like limbs. This animal is extremely common at the Burgess Shale and is a distant relative of insects and spiders.
The feeding claw of Anomalocaris, one of the largest predators from the Burgess Shale. This animal belongs to an early branch in the arthropod group, close to the common ancestor of insects, spiders, and crabs.
Getting fossils out of the mountains is no easy task! Here we employ a net suspended on a longline below a helicopter.
Given its protected status, collecting fossils at the Burgess Shale is by permit only. However, guided hikes are available to the intrepid fossil enthusiast through Parks Canada and the Burgess Shale Geoscience Foundation. For those unable to make the somewhat arduous journey to the site, a selection of Burgess Shale fossils are on permanent display in the Earth History Gallery of the Manitoba Museum.
As I begin my tenure here at the Manitoba Museum, I feel equally excited about the potential for fantastic scientific discoveries. A legacy of field work has yielded important collections from three Konservat-Lagerstätten here in Manitoba. At roughly 445 million year old, these deposits are slightly younger than the Burgess Shale. They therefore provide complementary snapshots of early animal diversification. I look forward to “digging into” these collections and sharing new insights in the coming years.
The Burgess Shale display in the Manitoba Museum, Earth History Gallery, featuring a selection of different organisms.
