Burgess Shale's Weird Wonders
The fossils found in the Burgess Shale include the 500-million-year-old ancestors of most modern animals
- By Smithsonian.com
- Smithsonian.com, July 16, 2009
(J.B. Caron, with permission of the Royal Ontario Museum and Parks Canada © ROM)
Sidneyia inexpectans is thought to be a carnivorous animal about four inches long that ate prey larger than trilobites and lived at the bottom of the ocean during the Cambrian Period. Sidneyia is potentially an ancestral member of a group of arthropods that include today’s spiders and horseshoe crabs.