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Geological Survey of Canada Expeditions and the Cambridge Group

In the mid-1960s, the Geological Survey of Canada (GSC) revisited the long-neglected Walcott and Raymond quarries to conduct further fieldwork. This was almost 80 years after the first fossil discoveries were made on nearby Mount Stephen by other GSC geologists. The GSC's work was especially significant because of its improved collecting methods.

The fossils collected served as the basis for a major revision of the Burgess Shale animals by Harry Whittington and the so-called "Cambridge Group" starting in the late 1960s. Detailed anatomical studies were made possible thanks to the application of a combination of observation and photographic techniques and the recognition that fossils retained some of their original dimensionality and were not completely flat, allowing for their careful preparation.

The work by the Cambridge Group helped reaffirm the dramatic nature of the Cambrian Explosion, which was subsequently popularized by Stephen Jay Gould and influenced research on other Burgess Shale deposits around the world.

Background

During the early 1960s, the GSC was actively involved in re-mapping the southern Rocky Mountains of Alberta and British Columbia using new methods and techniques. Harry Whittington, then Professor of Geology at Harvard University, contacted the GSC with a proposal to reinvestigate the Burgess Shale and reopen the Burgess Shale quarries. The proposal was soon expanded into a detailed paleontological, geological, and stratigraphic study of the Burgess Shale.

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Harry Whittington's Initial Visits to the Walcott Collections

Colour photograph of Harry Whittington posing in front of a cabinet containing fossils

Harry Whittington (1916-2010) at the University of Cambridge on September 27, 2002.

© The Palaeontological Association

The man who spearheaded the paleontological reinvestigation of the Burgess Shale in the 1960s was Harry Whittington. A world-renowned trilobite specialist, he joined Harvard University in 1949 as a Professor of Geology at the Museum of Comparative Zoology. He was later appointed Woodwardian Professor of Geology at Cambridge University in 1966 and continued his research on the Burgess Shale well after his retirement from Cambridge in 1983.

During his years at Harvard, Whittington visited the Burgess Shale collections at the Smithsonian Institution, which had been left almost untouched and ignored, just as Walcott probably left them at the end of the 1920s. (The exception was a preliminary study of the fossils started by Alberto Simonetta and Laura Della Cave in 1962, but not published until 1975.) At the time, the collection was difficult to access and was stored in the original building of the Smithsonian Institution. The collection was relocated in the 1960s to a new wing of the National Museum of Natural History, making it more accessible to researchers. Walcott's collection can still be found there today.

Prior to this move, researchers had to rely almost exclusively on Walcott's published descriptions and figures without being able to observe the actual specimens. But the original illustrations had many flaws, and Walcott himself acknowledged his publications were only intended as very preliminary accounts. Whittington quickly realized that new observations and reinterpretations of the fossils would be necessary.

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Whittington's Early Observations and Discoveries

As he made his first studies, Whittington discovered the fossils were not two-dimensional impressions (as Walcott had thought). In fact, they retained some of the original organism's three-dimensional structure, albeit highly compressed into very thin layers within the rock. This observation meant that when split open, the part and counterpart (opposing sides) of the same fossil could reveal minutely different levels of the specimen — and these needed to be studied together to provide a complete anatomical interpretation.

Colour photograph of Harry Whittington posing in front of a cabinet containing fossils

Harry Whittington observing fossils, at the GSC Burgess Shale campsite, 1966 or 1967.

© Geological Survey of Canada

Before the GSC collections, specimens from various layers had been collected and stored together, so very little information on the exact stratigraphic location of the fossils was available. In addition, the parts and counterparts of specimens collected by earlier expeditions had often been dispersed to different collections, making it difficult to reliably estimate the number of specimens present (and sometimes removing important morphological information which would have only been available with both sides of the fossil).

The specimens collected in 1966 and 1967 by the GSC would attempt to address these problems.

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Geological Survey of Canada (GSC) Excavations: 1966-1967

In 1966 the Survey's James Aitken (an expert on stratigraphy) led a party of thirteen, including Whittington and William Fritz (a GSC stratigrapher and expert on Cambrian trilobites). (David Bruton from the University of Oslo would join the 1967 field season.)

Black and white photo of people posing in front of a tent with a mountain in the background

The 1966 GSC expedition. From left to right, front row: Norman MacDonell; James Aitken; Peter Fritz; Dorothy Whittington, James Doyle, Henry Lambert. Back row: Robert Stesky; Terry Green; Judith Fritz; Harry Whittington; Clifford Johnson; William Fritz; Riba Nelson.

© Geological Survey of Canada. Photo: William Fritz

During the two field seasons (each lasting 6 weeks) about 70 cubic metres (88 cubic yards) of fine rock were carefully extracted and split, extending the Walcott Quarry by at least 12 metres (39.4 feet) to the north. Most of the fossils came from layers within a two metre (6 feet)-thick succession equivalent to the Phyllopod Bed, which had been excavated almost 50 years earlier by Walcott.

Black and white photograph of side of mountain, showing one area filled with snow

Fossil Ridge with the position of the Walcott Quarry (partially filled with snow) as it looked when the GSC started its 1966 excavation. The location of the GSC excavation is just to the left of the snow bank.

© Geological Survey of Canada. Photo: William Fritz

About 17 cubic metres (21 cubic yards) of rock were finely split from layers 22 metres (72 feet) above the Walcott Quarry, significantly extending the excavation made by Raymond in 1930. The GSC crew called this second site the Raymond Quarry to honour the Harvard paleontologist.


Solid line represents the limit of the GSC excavation still visible today in the Walcott Quarry. Dashed lines represent current excavation limits. The Raymond Quarry was extended by GSC and ROM crews.

© Parks Canada. Photo: John Niddrie

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Improved Collecting Methods

As the excavation continued, the exact level at which each fossil was found was measured from a fixed reference point and great care was taken to ensure parts and counterparts of specimens were kept together. This precise methodology was a significant improvement on earlier expeditions.

Photo of 7 people at work in a quarry

Harry Whittington (middle, back to camera) with 1966 crew next to the GSC excavation area on the right. The circle on the wall represents the reference point from which all levels within the quarry were measured.

© Geological Survey of Canada. Photo: William Fritz

At least 10,000 specimens were collected from the two quarries — but with the exception of two new genera, Echmatocrinus and Scolecofurca, most of the fossils represented species that had already been described. The expedition also obtained an almost-complete specimen of Anomalocaris, which later played a critical role in the reinvestigation of this animal (see below).

Photograph of people working in quarry on side of mountain.

Harry Whittington (third man from the front smoking a pipe, left side of image) with 1966 crew splitting the shale in the Walcott Quarry.

© Geological Survey of Canada. Photo: William Fritz

Photograph of fossil

Echmatocrinus brachiatus (part and counterpart) from the Burgess Shale discovered by the Geological Survey of Canada team.

© Geological Survey of Canada. Photo: William Fritz

In addition to being the first large Burgess Shale collections obtained using detailed sampling methods, the Geological Survey of Canada expeditions demonstrated the Walcott Quarry was still a productive source of fossils (which had been doubted after Raymond's 1930 excavation).

Black and white photo of men carefully removing a large slab of rock from a quarry

Excavation of a large slab on the north side of the Walcott Quarry at the beginning of the 1966 season.

© Geological Survey of Canada. Photo: William Fritz


Images from the Geological Survey of Canada 1966 expedition.

© Geological Survey of Canada. Photos: William Fritz

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Preparation Methods

Whittington was the first scientist to prepare fossils from the Burgess Shale anatomically, very similar to the dissection of a modern organism.

Whittington used a modified dental drill and prepared the fossils under a binocular microscope. The apparatus operated like a miniature jackhammer, driving a tiny chisel shaped from a carbide needle to remove minute flakes of both rock and fossil. He tested this tool on the small arthropod Marrella because it was the most common fossil in the Walcott collection (Walcott alone had collected more than 15,000 specimens). This technique proved so successful that it was used in all subsequent studies, leading to spectacular discoveries like the true nature of the animal Anomalocaris.

Colour photograph showing both halves of the same fossil

Anomalocaris canadensis (part and counterpart) collected by the GSC from the Raymond Quarry (GSC 75535). This specimen was prepared mechanically to reveal the claws and mouth parts attached to the body of the organism. Before this discovery, the different elements were interpreted as belonging to different organisms.

© Geological Survey of Canada. Photos: Jean-Bernard Caron

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Drawing and Photographic Methods

After mechanical preparation, the next step was to draw specimens using a camera-lucida attachment (a drawing tube with a mirror attached to a stereomicroscope). This allowed an observer to see both the fossil and its image reflected onto a sheet of paper for easy tracing of details. The method allowed researchers to identify fine differences in the different layers of the fossils and to interpret the features observed. Both preparation and drawing methods are still used today to study Burgess Shale fossils.

Colour photograph of a drawing station, including light source, stereo microscope and camera-lucida

A stereomicroscope equipped with a camera-lucida attachment (drawing tube with mirror on the right) of a similar type as the one used by the Cambridge group to draw Burgess Shale fossils.

© Royal Ontario Museum. Photo: Peter Fenton

These illustrations not only provide minute anatomical details (often by combining views from both part and counterpart together on the same drawing) but also help reveal different orientations of specimens within the rocks. (Some were buried laterally, others ventrally, dorsally or obliquely.)

Photography was also an important tool for illustrating the specimens. Burgess Shale fossils are notoriously difficult to photograph because they are preserved as reflective films. (Walcott addressed this problem by using a pencil to enhance his pictures prior to publication.) Whittington's photographs were taken with specimens immersed in alcohol or at an angle of about 65° from the fossils and using ultraviolet light. These methods produced the best results, particularly for the highly reflective areas of the fossils. High-quality images (often using low-angle light) could reveal different details of the fossils. In this way, multiple images could be used in addition to the drawings to support the detailed descriptions of the fossils. Today's photographic techniques build on these advances as well as using new tools.


Interpretative drawing and photos of Marrella splendens as illustrated by Whittington (1971).

© Geological Survey of Canada.

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Research by the Cambridge Group

The Cambridge group consisted of Harry Whittington and two of his former PhD students, Derek Briggs (who studied the fossil arthropods of the Burgess Shale) and Simon Conway Morris (who was assigned the fossil worms). Chris Hughes and David Bruton (the latter being the only member of this group who was not based in Cambridge) provided more modest contributions on the arthropods.

The Cambridge group employed a variety of traditional methods and techniques first demonstrated by Whittington, and which were applied to all subsequent descriptions of the organisms (see Preparation Methods, above). The result was a series of detailed descriptions of many species previously described by Walcott, but also some new ones which have since acquired a semi-mythical status in the field, such as Hallucigenia. (These studies were based on the fossils available at the time. New research methods and new fossils, most of which were discovered by subsequent ROM expeditions, has led to the reinterpretation of some of these species.)

 Photograph of fossil worm, showing clear 'spines'

Holotype of Hallucigenia sparsa described in 1977 by Simon Conway Morris (reversed from his original description).

© Smithsonian Institution - National Museum of Natural History. Photo: Jean-Bernard Caron.

Published taxa by the Cambridge group since 1971

Year Lead Author Phyla-level Animal Described
1971 Whittington Arthropod Marrella
1974 Whittington Arthropod Yohoia and Plenocaris
1975

Whittington

Hughes

Arthropod

Arthropod

Opabinia, Kootenia, Olenoides (1)

Burgessia

1976

Briggs

Conway Morris

Arthropod

Mollusc

Branchiocaris

Nectocaris, Odontogriphus

1977

Whittington

Briggs

Conway Morris

Arthropod

Arthropod

Arthropod-Lobopod

Indeterminate

Indeterminate

Priapulid

Naraoia

Perspicaris

Hallucigenia

Amiskwia

Dinomischus

Ottoia, Selkirkia, Louisella, Ancalagon, Fieldia, Scolecofurca, Lecythioscopa

1978

Whittington

Briggs

Conway Morris

Arthropod-Lobopod

Arthropod

Arthropod

Aysheaia

Canadaspis

Laggania

1979

 

Briggs

Conway Morris

Arthropod

Annelid

Anomalocaris

Canadia, Burgessochaeta, Insolicorypha, Peronochaeta, Stephenoscolex

1980 Whittington Arthropod Olenoides, Nathorstia (2)
1981

Whittington

Briggs

Bruton

Arthropod

Arthropod

Arthropod

Molaria, Habelia, Sarotrocercus, Actaeus, Alalcomenaeus

Odaraia

Sidneyia

1983 Bruton and Whittington Arthropod Emeraldella and Leanchoilia
1985

Whittington

Whittington and Briggs

Conway Morris

Arthropod

Arthropod

Mollusc

Tegopelte

Anomalocaris

Wiwaxia

1993 Conway Morris Indeterminate Thaumaptilon, Mackenzia, Redoubtia (=Gelenoptron)
1998 Whittington Arthropod Hanburia

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Research Contributions from GSC Geological Studies

In addition to the paleontological discoveries about the Burgess Shale fauna coming from the Cambridge group, the GSC's geological studies produced important results as well.

Perhaps the most significant discovery was made when William Fritz realized the Burgess Shale was deposited along the base of a submarine cliff (today called the Cathedral Escarpment) within the "thick" Stephen Formation. This cliff was thought to have provided ideal conditions not only for the development of a rich ecosystem, but also for its spectacular preservation in this particular area. It was subsequently discovered that this structure can be found in other areas in Yoho and Kootenay National Parks, where it is often associated with Burgess Shale-type fossils. At the same time, researchers recognized the Burgess Shale organisms had been buried quickly in a succession of fine deposits of flowing mud.

These geological breakthroughs, combined with the detailed paleontological work of the Cambridge group, paved the way for a thorough investigation of the Burgess Shale community as a whole. This summary study was published in 1986 by Simon Conway Morris. In some ways it represented the integration of the entire body of work published by the Cambridge group since the first GSC expedition twenty years earlier.


Cross-section of formations showing the position of the Burgess Shale along the Cathedral Escarpment next to the Cathedral Formation.

© William Fritz

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The Conway Morris Community Study: 1986

Conway Morris tabulated every specimen on all the slabs in the Walcott and GSC collections from the Walcott Quarry that he could find. Before this painstaking survey, nobody had any idea how big the Walcott collection actually was. The numbers were astonishing: 35,520 slabs observed, 73,300 specimens counted. Of these, about 65,000 specimens had been collected by Walcott, the rest were collected by the GSC expeditions of 1966 and 1967. (The Walcott collection represented by far the largest collection of fossils from the Burgess Shale until it was surpassed by the ROM's own Burgess Shale collection at the end of the 1990s.

In addition to revealing the importance of predation in the Burgess Shale ecosystem, Conway Morris suggested the structure of the Burgess Shale community was typical of what other marine communities in similar environments during the Middle Cambrian would have looked like. This conclusion was soon confirmed with the discovery of other deposits of Burgess Shale-type fossils. Conway Morris's study also emphasized that without the exceptional preservation of soft tissues found in the Burgess Shale, about 86% of the genera (representing the majority of the specimens) in this community would have been lost to decay and left no trace in the fossil record.

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Legacy of the Cambridge Group Work: The Cambrian Explosion

The work of the Cambridge group played a critical role in re-igniting interest in the Burgess Shale and soon led to further discoveries elsewhere — notably in China. One of the main surprises the Cambridge group encountered was the fact that many organisms from the Burgess Shale did not fit easily into modern groups of animals. These studies dramatically emphasized the rapid appearance and diversity of animals during the Cambrian, and were pointed to as evidence for the "Cambrian explosion".

Colour photograph of a reproduction of the Burgess Shale ecosystem, featuring many different animals and sponges

Burgess Shale diorama inspired by the work of the Cambridge group, showing the living community at the bottom of a submarine cliff. You can compare this diorama with a more recent virtual recreation of the Burgess Shale ecosystem on a virtual dive.

©Smithsonian Institution - National Museum of Natural History. Photo: Jean-Bernard Caron

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Stephen Jay Gould Spreads the Word: 1989

The work of the Cambridge group reached a much larger audience in 1989 with the publication of Stephen Jay Gould's best-selling book, Wonderful Life: The Burgess Shale and the Nature of History.

Gould's main hypothesis was the possibility that many Burgess Shale organisms described by the Cambridge group represented potential new phyla, which he evocatively called "weird wonders". This suggested that the diversity of phyla was greater in the Cambrian than it is today. Over the course of history, chance alone would have wiped out most groups, leaving a lucky few to evolve to the present.

Black and white drawing of Hallucigenia, showing the creature walking by using spikes as legs

Historical reconstruction of Hallucigenia by Marianne Collins in "Wonderful Life". This animal has since been reinterpreted, meaning in this image it is depicted upside down.

© Marianne Collins


Gould's talk at the Royal Ontario Museum.

© Royal Ontario Museum

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The Burgess Shale GSC Collection today

After travelling to Cambridge for study in the 1970s, the new GSC specimens were housed at the GSC in Ottawa. They are the second-largest collection of Burgess Shale fossils in Canada, after the ROM. They reside close to older collections, principally from Mount Stephen, made decades earlier by McConnell and several other geologists from the GSC.

On left, long row of metal cabinets. On right, worker looks at fossils in a drawer pulled out of a cabinet.

Geological Survey of Canada collections in Ottawa. Left, overview of collections; right, Burgess Shale 1966-1967 collection area.

© Geological Survey of Canada. Photos: Jean-Bernard Caron

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