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Pikaia eberly college

Reconstruction of Pikaia

Pikaia was a chordate from the Middle Cambrian of the Burgess Shale.

DescriptionEdit

Pikaia was a long, leaf-shaped creature measuring 5 centimeters or less in length. It had a pair of tentacles on its front end, and possible gill slits on the side of its body.[1] It was similar in morphology to the modern lancelets,[2] and was probably a slow swimmer.[3]

The first signs of heads in animals are seen in Pikaia and similar fossils. It is believed that the front end of animals containing the mouth, being the first part of the body to come into contact with food, needed additional sensory equipment in order to find food more easily. This necessitated larger nerves in that body region to interpret the information gathered by these structures, resulting in the development of the brain.[4]

ClassificationEdit

Simon Conway Morris classified Pikaia as a primitive chordate, making it possibly one of the earliest ancestors of modern vertebrates.[5] However, not all paleontologists support this view.[6]

DiscoveryEdit

The first and only species, Pikaia gracilens, was discovered in the Burgess Shale in Canada and described by Charles Walcott in 1911. It was named after Pika Peak, a mountain in Alberta. Walcott first identified the animal as a type of marine worm. Only 16 specimens of Pikaia have been found to date in the Burgess Shale.[7]

ReferencesEdit

  1. Conway Morris, S.; Caron, J. B. (2012) "Pikaia gracilens Walcott, a stem-group chordate from the Middle Cambrian of British Columbia. Biological Reviews 87: 480-512.
  2. Delsuc et al. (2008): Additional Molecular Support for the New Chordate Phylogeny. - Genesis, 46(11): 592-604 PDF
  3. Lacalli, T. (2012). "The Middle Cambrian fossil Pikaia and the evolution of chordate swimming". EvoDevo 3 (1): 12. doi:10.1186/2041-9139-3-12. PMC 3390900. PMID 22695332. edit
  4. Palmer, D., (2000). The Atlas of the Prehistoric World. London: Marshall Publishing Ltd. p66-67.
  5. Conway Morris, Simon. 1998. The Crucible of Creation: The Burgess Shale and the Rise of Animals. Oxford University Press, New York, New York.
  6. Butterfield, N.J. (1990), "Organic preservation of non-mineralizing organisms and the taphonomy of the Burgess Shale", Paleobiology (Paleontological Society) 16 (3): 272–286, JSTOR 2400788
  7. "Pikaia gracilens" Burgess Shale Fossil Gallery. Virtual Museum of Canada. 2011.

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