Pikaia has a head and flexible cord running the length of its body. It was related to the ancestor of all backboned animals. This fossil of Pikaia gracilens was collected from the Burgess Shale site by Dr. Charles Walcott.


Cambrian seas swarmed with an amazing assortment of new animals living in novel ways. Nearly all of today’s major groups of animals arose in this ancient explosion of evolution. What set it off?

Rising oxygen levels, mild temperatures, and higher sea levels made Earth more hospitable to ocean life. Some animals began living higher in the water, while others burrowed in the sea floor. Some hunted other animals, and many evolved new defenses.


  • Title: Fossil of Pikaia gracilens
  • Location: Burgess Shale Formation, British Columbia, Canada, North America
  • Physical Dimensions: L: 4.5 W: 6.4 D: 1.2
  • Type: Fossil
  • Rights: This image was obtained from the Smithsonian Institution. The image or its contents may be protected by international copyright laws. http://www.si.edu/termsofuse
  • External Link: View this object record in the Smithsonian Institution Collections Search Center
  • USNM Catalog Number(s): PAL57628
  • Scientific Name: <i>Pikaia gracilens Walcott</i>
  • Photo Credit: Chip Clark, Smithsonian Institution National Museum of Natural History
  • Geologic Age: Paleozoic - Cambrian - Middle
  • Field: Paleobiology

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