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Re-examining the Burgess Shale David B. Williams EARTH Vol. 54 (No. 8), p. 30

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www.earthmagazine.org A of surprises for scientists. scientists. for surprises of lot a have still — drawers museum in sitting currently tions for a century, creatures the fossil site — and especially the unique fossil collec- and bizarre for Shale Burgess the mining been have scientists Although Shale. Burgess the of covery says. he animals,” with teeming “that’sliterally planet a find paleontologists rocks, Cambrian in But microbes. of smattering a for except life of divide, the world, or at least the rock record, appears devoid the Before record. geologic the in divide fundamental a calls Explosion (540 million to 525 million years ago), which Gaines Cambrian the — evolution in events critical most the of one highlight creatures, soft-bodied of especially diversity, and abundance unique site’s The Calif. Claremont, in College in the world,” says Robert Gaines, a paleoecologist at Pomona Shale. Burgess preservedthebeautifully arein creatures Today, these sediments. muddy the in accumulated bodies their where base, its at deposited and reef the over washed get would animals Periodically,the bottom-dwellers. small relatively were which of most organisms, of array diverse a the continent, however, hosted a carbonated reef teeming with B.David Williams fossil site stillholdssurprises discovered, theworld’s mostfamous A hundred years itwas after Re-examining theBurgessShale Trends andInnovations 30 hs ot mrs h cnena anvray f h dis- the of anniversary centennial the marks month This “The Burgess Shale is arguably the most important fossil site 

EARTH August 2009 ren landscape. The warm, shallow sea bordering bordering sea shallow warm, The landscape. ren no terrestrial plants or animals, the land was a bar- become North America straddled the equator. With bout 505 million years ago, the continent that would affair, as his wife and several of their children joined him. him. (Walcott joined honored his son Sidney children by naming their the first of formally several and wife his as affair, family a was Collecting Canada. Alberta, in Banff of west Wapta Mountain and Mount Field, about 70 kilometers north- years, Walcott returned seven times to his quarry site between 15 next the Over camp.” to samples fine of number large a Took Crustaceans. Phyllopod of group remarkable a found seen. ever had paleontologist, other any or he, any as fossil crustaceans. They were, however, crustaceans unlike smooth, dark gray rocks dotted with what Walcott recognized Columbia’s Yoho National Park, when he observed numerous on a steep rocky slope, high in the Canadian Rockies in British was He 1909. 31, Aug. on locality Burgess the discovered he when decades four than more for fossils collecting been had D.C., Washington, in History Natural of Museum National He drew three of the fossils in his diary and wrote, “We wrote, and diary his in fossils the of three drew He hre Doite act, ietr f h Smithsonian’s the of director Walcott, Doolittle Charles The Find The www.earthmagazine.org

Bottom: Courtesy of the Smithsonian Institution; top: Robert Gaines described fossil from the Burgess The Site Sidneyia inexpectans.) They eventually Once an unknown and isolated collected more than 65,000 specimens, mountainside, the Burgess Shale quar- now housed at the Smithsonian. ries became a UNESCO World Heritage Walcott hoped to write a definitive Site in 1981 to prevent over-collecting of study on his Burgess fossils. He pub- fossils. Located between Mount Field lished his first paper in April 1910 and and Wapta Mountain, Walcott’s original another five over the next decade. He quarry has produced many of the best called these preliminary reports, but he fossils. In 1924, Harvard University pro- never went further. The site remained fessor Percy Raymond opened a second somewhat in anonymity until the 1960s, quarry. Recently, researchers have also when paleontologist Harry Whittington started to find other fossil-bearing sites and two paleontology graduate students on nearby mountains. at Cambridge University in England, The dominant fossils found to date Simon Conway Morris and Derek Briggs, are arthropods, the largest animal phy- began working on the site. lum, which includes insects, spiders and

Top left: Burgess Shale discovery site in the Canadian Rockies today. Left and below: Charles Walcott and his crew as they discovered the Burgess Shale in 1909.

Top: Burgessia bella, a Middle Cambrian arthropod found in the Burgess Shale, lived about 505 million years ago. Above: Jean-Bernard Caron at the Burgess Shale site in 2007. Below: Caron at the site in 2008. Bottom left: Courtesy of the Smithsonian Institution; bottom right: Robert Gaines; top and middle right: With permission of Parks Canada © Royal Ontario Museum 2008. Photo Credit: J.B. Caron. All rights reserved. All Caron. J.B. Credit: Ontario Museum 2008. Photo © Royal Canada left:permissionBottom of Parks CourtesyWith of the Smithsonian Institution; right: Robert bottom Gaines; and middle right: top

www.earthmagazine.org EARTH August 2009  31 mal means of decay in marine sediments sils from 11 sites. sites. 11 from sils Shale-type fossilization, based on 53 fos- proposed a new mechanism for Burgess recently has Gaines says. he again?’” this way?’ and ‘Why does it not happen preserved fossils these were ‘Why are says. Gainesprocess,” of type singular eyes and gills preserved as carbon. It’s guts, a are seeing are we “What fossils. compression two-dimensional as biota locality, dark-colored films preserve the Burgess Shale-type fossilization. In each of component minor a containing so or and one in Greenland — with another 40 in Canada, three in China, three in Utah sites occur throughout the world — two fossilization. Shale-type Burgess as preservation of mode this to refer now paleontologists that rare so is preservation such fact, In an unprecedented level of preservation. soft-bodied, are fauna preserved the of percent 85 than more that is science to valuable so Burgess the makes what of Part dinoflagellates. and bacteria teria, cyanobac- organisms single-celled the with along abundance, in found been ancestor, earliest our (perhaps chordate one and pens sea worms, sponges, But trilobites. as such groups extinct as well as crustaceans, Trends andInnovations couple years ago.years couple a re-examined and Museum Ontario Royal the of drawers the in rediscovered was fossil The Walcott. Charles by collected most The Below: of specimen fossil . victoria well-preserved Hurdia of Reconstruction Right: 32 “Two central questions of the Burgess Nine high-quality Burgess Shale-type Central Central to his argument is that the nor- 

EARTH August 2009 Pikaia ), have also have ), , which was which , victoria Hurdia larly after the publication of Stephen Jay intense upturn in the late 1980s, particu- modern animals? The discussion took an and biota Burgess between the tionship unusual environment? What is the rela- an in preserved finally biota evolved had only recently evolved, or were long- for the preservation of unusual biota that environment 540 million years ago the allow in change some Did evolution: in led to even more fundamental questions of Cambrian life in the Burgess Shale has the complete and well-preserved record of discovery the but connect, evolution of branches ancient how debated have record.”sil fos- thepreservation inof unique type a to led “It says. he ocean,” today’s in occur longer no which of most ates, carbon- the of deposition chemical the to contributed processes “Several ers. sealed them from microbial decompos- which fossils, the atop developed ates a chemical cement of inorganic carbon- beds of clay-sized particles. Secondarily, under them entombed and ocean the landslide carried the animals deep into a a or as current turbidity muddy,swirling such event an suggests, Gaines weeks and not been preserved. Initially, in down broken have would tissues otherwise suppressed; been have must Biologists Biologists since at least Charles Darwin Evolution houses the largest collection of Burgess Burgess of collection largest the houses which Canada, in Museum Ontario of invertebrate paleontology at the Royal insights. new produced thoroughly examined in years — has also of museum collections that haven’t been investigations new and fieldwork both China. New work on the Burgess itself — primarily the older Chengjiang fossils in ies of other Burgess Shale-type deposits, mering questions, prompted by discover- gotten better insights into these long-sim- life. of tree branching ally paradigm of a continuously and gradu- the upsetting by part in and Walcott, treated he way the of because part in Gould’sconclusionpeople,manyupset plans. body failed many to led which a time of evolutionary experimentation, his view, the Burgess Shale represented In Cambrian. the since existed not had and existed longer no that groups from of the animals seen in the Burgess were view of life.” Gould proposed that many conventional his from directly arising manner consistent thoroughly and sive interpreted these fossils in a comprehen- fossillineages. To Gould,Walcott “mis- most of them into established groups of “shoehorned,” say, some as or placed, “Wonderful Shale, Life.” Burgess the on book Gould’s landmark When Walcott studied his fossils, he he fossils, his studied Walcott When Jean-Bernard Caron, associate curator have paleontologists recently, More www.earthmagazine.org

Bottom: Collected by Walcott. Image © Science/AAAS; top: Drawing by Marianne Collins (2008). Image © Science/AAAS. Five fossil images: With permission of Parks Canada © Royal Ontario Museum 2008. Photo Credit: J.B. Caron. All rights reserved; bottom center and middle left: Robert Gaines anomalocaridid called and realized they actually had only one animal, an from what they werethought eight taxa different carapaces frontal and appendages front parts, body and mouth examined team the collections, Museum’sOntario Royal the from material with on an even more bizarre creature. Again working Uppsala University in Sweden and others to report Shale. Burgess the of creatures the into re-examination his of start paper,the Nature 2006 species in this group. He reported his findings in a indeed a mollusk and one of the oldest soft-bodied examined the fossil, he realized chiopods and colonial bryozoans. When Caron re- must be a lophophore, the group that includes bra- mollusks, he finally concluded that this new animal excluding flat worms and ribbed worms, as well as animal (some thought it looked like roadkill). After drawers, didn’t know specimen what to make of the the unusual in animal the discovered who gist paleontolo- the Morris, Conway Simon first, At called 1974 in Smithsonian the of vaults the in discovered first genus a was mens speci- the Among specimens. new 189 examined Burgess. the fromspecimens 150,000 the access to researchers other allow to programs collaborative and integrated of series a develop to was 2006 in museum the at working started he Burgess resurgence. One of the Caron’s for principle projects when force driving a been has fossils, www.earthmagazine.org ao as tae wt Alsn . ae of Daley C. Allison with teamed also Caron In the first study to result from the project, Caron The Burgess Shale is arguably the most important fossil site in the world.the in site fossil important most the arguably is Shale BurgessThe . Hurdia Up to 30 centimeters was Odontogriphus was — Robert Gaines, PomonaCollegeGaines, Robert — Odontogriphus. origin has always been a question, Caron says, and limb Arthropod arthropods. modern of ancestors ancient the of relationships clarify helps Hurdia Cambrian. the voraciousof a predator great size and pencil sharpener-mouth made head. like with five rows of teeth, and an armored, blue whale- long, See See His Wash. latest book, “Stories Seattle, in Stone,” in was published in June. writer freelance a is Williams Shale.” Burgess the for bright quite is future activity, “the says, Caron hence what might not be preserved. With and so much preserved are fossils how understanding in aids and composition mineral highlights which for better interpretation and “elemental mapping,” microscopeselectronScanningallowtrees.family sils to do cladistic work, or studies of evolutionary fos- enough paleontologists given have collecting says. more for allowing and collections the up Caron Opening studies,” our drive helped have Walcottthought. Gould wasthan correct more with modern lineages of arthropods and shows that that evolution. The new in work places step early an show might lobes Hurdia’s series of flaps, or lobes, bearing gill-like blades. Its canadensis. of specimen complete Cambrian; Middle the from mollusk a omalus, Odontogriphus arthro- from jaw Cambrian possible pod; Middle another canadensis, of part front ago; years million 505 splendens, an arthropod from the Middle Cambrian, bottom: to top from fossils Shale Burgess Alison Daley in Walcott’s original quarry in 2008. in Walcott’sin Daley Alison quarry Below: original 2008. in Stephen Mount on locality Shale Burgess a atStreng Michael Loxtonand Jason Left: From an evolutionary perspective, fleshing out out fleshing perspective, evolutionary an From “Several new techniques and new approaches approaches new and techniques new “Several www.storiesinstone.infoinformation.more for Hurdia Hurdia had peg-like eyes, a circular mouth mouth circular a eyes, peg-like had did not have legs but did havedida havebut legsnot did nmlcrs canadensis; Anomalocaris Hurdia more in line Anomalocaris Anomalocaris Anomalocaris Marrella Hurdia EARTH

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