Jamoytius

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Jamoytius
Temporal range: Silurian
Jamoytius kerwoodi.jpg
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Hyperoartia or Anaspida
Genus: Jamoytius
Species: Jamoytius kerwoodi
White 1946[1]

Jamoytius kerwoodi was a species of primitive, eel-like jawless fish that lived in the Silurian period.

J. kerwoodi is the earliest known anaspid.[2] It had long, paired fins running along its body - making it a good swimmer. J. kerwoodi resembled a lamprey, especially with its rounded mouth and elongated body. However, as it had no teeth or teeth-like structures in its mouth, it was not carnivorous like its distant modern-day relative, the lamprey. It was more likely to have been a filter-feeder or a detrius-feeder, possibly in the manner of larval lampreys.

The fish had a cartilaginous skeleton, and a branchial basket resembling the cyclostomes - used to suggest that it was a near-ancestor to that clade. It is also the earliest known vertebrate with camera-type eyes.[3] It also possessed weakly mineralised scales.[4]

History of research[edit]

Jamoytius was originally named by Errol White on the basis of two specimens (the generic name is a reference to J. A. Moy-Thomas[5]) and, at the time, it was considered to be the most basal vertebrate known. Since then, it has been reclassified by many workers as having many different affinities, such as an "unspecialized anaspid",[6] or as a sister taxon to the lampreys[citation needed], its difficulty in classification due to difficulties in reconstructing the anatomy;[7] it does not possess any usual chordate synapomorphies.

Further reading[edit]

  • Long, John A. The Rise of Fishes: 500 Million Years of Evolution Baltimore: The Johns Hopkins University Press, 1996. ISBN 0-8018-5438-5

Links to images[edit]

References[edit]

  1. ^ White, E.I. (March 1, 1946). "Jamoytius kerwoodi, a new chordate from the Silurian of Lanarkshire [Scotland]". Geological Magazine 83 (2): 89–97. doi:10.1017/S0016756800082856. Retrieved 2007-10-31. 
  2. ^ "New Page 4". Archived from the original on 2012-07-20. [dead link]
  3. ^ Ritchie, A. (1968). "New evidence on Jamoytius kerwoodi White, an important ostracoderm from the Silurian of Lanarkshire, Scotland" (PDF). Palaeontology 11: 21–39. Retrieved 2007-10-31. 
  4. ^ Today, G.; Blom, Henning; Märss, Tiiu (2003). "Fossils explained 43: Anaspid fishes". Geology Today 19 (3): 111–113. doi:10.1046/j.1365-2451.2003.00413.x. 
  5. ^ Dawkins, Richard The Ancestor's Tale
  6. ^ Ritchie, A. (1960). A new interpretation of Jamoytius kerwoodi White. 
  7. ^ Sansom, Robert S; Kim Freedman; Sarah E Gabbott; Richard J. Aldridge; Mark A. Purnell (2010). "Taphonomy and Affinity of an Enigmatic Silurian Vertebrate, Jamoytius Kerwoodi White". Palaeontology 53 (6): 1393–1409. doi:10.1111/j.1475-4983.2010.01019.x.