Metaspriggina

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Metaspriggina
Temporal range: Burgess Shale
Metaspriggina and Maripolia.png
An artist's concept of Metaspriggina based on Conway Morris, Caron.[1]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
(unranked): Craniata
Genus: Metaspriggina
Species: M. walcotti
Binomial name
Metaspriggina walcotti

Metaspriggina is a genus of chordate initially known from two specimens in the Middle Cambrian Burgess Shale[2] and 44 specimens found in 2012 at the Marble Canyon bed in Kootenay National Park.[1]

Reconstruction of Metaspriggina based on the Burgess Shale specimens available then.[2][3]

Whilst named after the Ediacaran organism Spriggina, later work has shown the two to be unrelated.[2] Metaspriggina is considered to represent a primitive chordate, possibly transitional between cephalochordates and the earliest vertebrates. It lacked fins and had a poorly developed cranium, but did possess two well-developed upward-facing eyes with nostrils behind them.

Metaspriggina also possessed a notochord, along with seven pairs of pharyngeal bars, possibly made of cartilage. The largest specimens are 10 centimetres (3.9 in) in length. Originally believed to be free-swimming but occasionally found on the sea floor,[3][4] the fossils from Marble Canyon showing the presence of eyes and their placement suggests it lived as a filter-feeder swimming above the sea floor. The exceptional preservation at Marble Canyon also preserved muscle detail, showing that the animal moved with a side-to-side swimming motion.[1]

The discovery of pharyngeal bars (gill bars) makes Metaspriggina the oldest known animal to have this feature.[1] The first pair of pharyngeal bars later evolved to form the upper and lower jaws of vertebrates.

References[edit]

  1. ^ a b c d Conway Morris, Simon; Caron, Jean-Bernard (June 11, 2014). "A primitive fish from the Cambrian of North America". Nature (London: Nature Publishing Group). doi:10.1038/nature13414. ISSN 0028-0836. Retrieved 2014-06-13. 
  2. ^ a b c Conway Morris, Simon (March 2008). "A Redescription of a Rare Chordate, Metaspriggina walcotti Simonetta and Insom, from the Burgess Shale (Middle Cambrian), British Columbia, Canada". Journal of Paleontology (Boulder, CO: The Paleontological Society) 82 (2): 424–430. doi:10.1666/06-130.1. ISSN 0022-3360. Retrieved 2014-06-13. 
  3. ^ a b "Metaspriggina walcotti". Burgess Shale Fossil Gallery. Virtual Museum of Canada. 2011. 
  4. ^ Smith, M. Paul; Sansom, Ivan J.; Cochrane, Karen D. (2001). "The Cambrian origin of vertebrates". In Ahlberg, Per Erik. Major Events in Early Vertebrate Evolution: Palaeontology, Phylogeny, Genetics and Development. London; New York: Taylor & Francis. pp. 67–84. ISBN 0-415-23370-4. LCCN 00062919. OCLC 51667292. 

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