Invertebrate Zoology – ZOOL 3104

Burgess Shale

How are fossils made?

• Animal is buried (dead or alive)– Mud, silt, volcanic ash, or sand

• Fossils could also be frozen in ice, mummified in hot or cold deserts, or preserved in tar

• Usually, all of a living thing’s soft parts decay, leaving only the hard parts

How are fossils made II

• Replacement: the minerals replace, molecule by molecule, the hard parts or the remains

• Permineralization: minerals fill in the spaces of the hard parts of the remains

Burgess Shale

• Made famous to the general public by Stephen Jay Gould. 1989. Wonderful Life: The Burgess Shale and the Nature of History

Burgess Shale

• Shale is a sedimentary rock formed by the deposition of successive layers of clay.

Burgess Shale

• Shale is a sedimentary rock formed by the deposition of successive layers of clay.

• Located in Yoho National Park in the Rocky Mountains, near Field, British Columbia, Canada.

Burgess Shale

• Shale is a sedimentary rock formed by the deposition of successive layers of clay.

• Located in Yoho National Park in the Rocky Mountains, near Field, British Columbia, Canada.

• Cambrian rock formation over 500 million years.

Burgess Shale

• Shale is a sedimentary rock formed by the deposition of successive layers of clay.

• Located in Yoho National Park in the Rocky Mountains, near Field, British Columbia, Canada.

• Cambrian rock formation over 500 million years.

• So, what is so special about it?

A unique place

• Exceptional preservation of soft bodied marine invertebrates.

• Over 65,000 fossil specimens of 120 species from the Burgess Shale are housed at the Smithsonian.

Burgess Shale

How preservation works?

• Good preservation indicates deposition in anoxic conditions

How preservation works?

• Good preservation indicates deposition in anoxic conditions

• Many delicate details of soft part anatomy are preserved. (Legs and gills of trilobites, etc.)

How preservation works?

• Good preservation indicates deposition in anoxic conditions

• Many delicate details of soft part anatomy are preserved. (Legs and gills of trilobites, etc.)

• Swept off an adjacent, well-oxygenated carbonate platform by turbidity currents, and killed and protected from decay in anoxic water

http://burgess-shale.rom.on.ca/en/sea-odyssey/catastrophic-burial.php

The initial discovery

• Charles D. Walcott (1909)

• Secretary of the Smithsonian Institution

(1850-1927)

Charles D. Walcott

The Animals

• Mud dwellers, filter feeders

• Strollers, walkers and crawlers

• Swimmers and floaters

Filter Feeders

• P: Porifera

Filter Feeders

• P: Echinodermata: C: Crinoidea

Mud Dwellers:

• C: Polychaeta (P: Annelida)

Strollers, walkers and crawlers• P: Onychophora

Strollers, walkers and crawlers• P: Onychophora

Strollers, walkers and crawlers• P: Onychophora

Hallucigenia sparsa an Onychophoran from the Burgess Shale deposits of Canada

Strollers, walkers and crawlers• Unknown phylum Wiwaxia

Strollers, walkers and crawlers

• P: Arthropods

Swimmers and floaters

• P: Arthropoda: SP: Trilobites

Swimmers and floaters

• P: Ctenophora, and Cnidaria

Weird Creature Award

• P: Arthropoda

Weird Creature Award

Weird Creature Award

• Anomalocaris over 12 inches long!

The world’s first known chordate

• Pikaia

The Big Picture

• Fossilization usually takes place only of hard parts

• The Burgess Shale is unique in that it fossilized soft tissues

• Many creatures fossilized in the shale are extinct and were truly unique.