Burgess shale

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The Burgess shale is a geological formation cropping out in the Canadian Rocky Mountains. This formation yields abundant, exceptionally preserved fossils of Middle Cambrian age, and thus constitutes a fundamental window in the early evolution of life.

The fossil lagerstätten of Burgess was discovered by geologist Charles Doolittle Walcott in 1909, who excavated the site since 1910. Its existence was made known that same year[1], and since then it became the object of numerous studies.

The fossil fauna of Burgess preserves soft parts - a case of exceptionally good fossilization - and this is the reason why it is so rich. In the Middle Cambrian, in fact, organisms with hard parts as shells or bones were still rare. It is mostly constituted by extinct fossil groups which did not leave descendants, hence its paramount importance for the modern evolutionary theory.

The history of studies on the Burgess fauna, and its cultural and scientific importance, are beautifully narrated in Gould's book "Wonderful life"[2]

References and notes

  1. Walcott, C.D., 1910, Abrupt appearance of the Cambrian fauna on the North American continent. Cambrian Geology and Paleontology, II, Smithsonian Miscellaneous Collections, 57, 1-16
  2. Gould, S.J., 1990, Wonderful life: The Burgess Shale and the Nature of History. W.W. Norton, 352 pp., ISBN 039330700X