Fossilized footprints lead researchers from the Royal Ontario Museum and the University of Saskatchewan and to an unexpected culprit
Researchers from the University of Saskatchewan and Royal Ontario Museum (ROM) have used the first animal trackways from the Burgess Shale to breathe life into scientific understanding of the locomotion and mode of life of a long extinct arthropod.
The 500-million-year-old Burgess Shale of Canada is famed for its weird and wonderful fossils of marine organisms and the information that they provide on evolution during the Cambrian explosion, a period approximately 500 million years ago that was characterized by a very large growth in animal diversity over a short period of time. Some of these animals also left behind more than just their bodies.
“Most researchers have focused previously on the body fossils of the Burgess Shale,” said Dr. Mángano, Associate Professor , University of Saskatchewan, and co-author of this research. “However studying its trackways, trails and burrows may dramatically impact our understanding of these ancient ecosystems.”
The most significant trackways were collected during a ROM field expedition in 2008 along the flanks of Mount Field, British Columbia, in Yoho National Park. Findings of the study were published November 9, 2011 in the Royal Society journal Proceedings of the Royal Society B, in an article entitled “Skimming the surface with Burgess Shale arthropod locomotion.” The study was co-authored by Dr. Jean-Bernard Caron,ROM Curator, Invertebrate Palaeontology, who led the Museum’s expedition in 2008.
Although Dr. Caron sighted a portion of the largest trackway in 2000, most was left behind as it could not be carried safely from its remote site without helicopter support. Not until 2008 were additional fragments of this particular trackway collected by delicately separating them from the associated bed layers. All of the pieces were then delicately packed, carried out by helicopter and shipped to the ROM.
“It is remarkable to think that the sediment layers of the Burgess Shale which were deposited at the bottom of an ocean 500 million years ago can now be found about 2,300 metres above sea level and reveal so much about past life.” said Dr. Caron.
Fossil trackways and other fossilized evidence of animal activities such as burrows, bite marks and faeces are known as trace fossils. Trace fossils provide direct evidence as to where animals were living and what they were doing, but the full identity of the producers is rarely known. The exceptional size of the trackways and the number of legs needed to make them resulted in only one suspect—Tegopelte—a caterpillar-like animal with a smooth dorsal carapace, one of the largest arthropods to roam the Burgess Shale seafloor. This creature had 33 pairs of legs and could reach up to 30 centimetres in length. All other animals living on the seafloor at the time were both too small and had too few legs to have made the trackways.
“Short of finding an animal at the end of its trackway, it's really very rare to be able to identify the producer so confidently.” said Dr. Minter, the lead author of this study and Post-doctoral Research Fellow, University of Saskatchewan, Department of Geological Sciences.
By analyzing both the fossilized remains of Tegopelte and the trackways, the researchers were able to reconstruct how this animal would have walked. Tegopelte was capable of skimming rapidly across the seafloor, with legs touching the sediment only briefly. The study supports the view that Tegopelte was a large and active top carnivore. Such lifestyles would have been important in shaping early marine communities and evolution during the Cambrian explosion.
About the ROM’s Burgess Shale Research:
The ROM is a major contributor to the study of the Burgess Shale and the fascinating creatures found therein. The Museum has led dozens of field explorations and excavations since 1975 and now holds the world’s largest collection of Burgess Shale specimens, over 150,000 in total. Today, ROM Curator Dr. Jean-Bernard Caron continues to lead field expeditions and to conduct research on Burgess Shale fossils with his colleagues and students. Highlights from the ROM’s extensive Burgess Shale collections will be on permanent display in the future Gallery of Early Life, and on the Virtual Museum of Canada Burgess Shale website to be launched in December 2011, a collaboration between the ROM and Parks Canada.
To learn more about the ROM's Burgess Shale collection and ongoing research, visit:
This research was supported through a Government of Canada Post-doctoral Research Fellowship under the Canadian Commonwealth Scholarship Program (N.J.M.), by Natural Sciences and Engineering Research Council (NSERC) Discovery Grants and University of Saskatchewan Start-Up fund (M.G.M). Jean Bernard Caron’s research is supported by an NSERC Discovery Grant and ROM research and fieldwork grants.
The trackways were collected under Parks Canada Research and Collecting permits to the ROM and are now reposited at the ROM. Managed by Parks Canada in Yoho National Park, the Burgess Shale was recognized in 1981 as one of Canada’s first UNESCO World Heritage Sites. Now protected under the larger Rocky Mountain Parks UNESCO World Heritage Site, the Burgess Shale attracts visitors to Yoho each year for guided hikes to the restricted fossil beds from July to September.
Minter, N. J., Mángano, M. G. and Caron, J.-B. in press. Skimming the surface with Burgess Shale arthropod locomotion. Proceedings of the Royal Society B. doi:10.1098/rspb.2011.1986
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