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Jamoytius

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

Jamoytius
Temporal range: Llandovery
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Order: Jamoytiiformes
Family: Jamoytiidae
Genus: Jamoytius
Species:
J. kerwoodi
Binomial name
Jamoytius kerwoodi
White, 1946[1]

Long thought of as a "basal anaspid," J. kerwoodi is now recognized as the best-known member of the Hyperoartian order Jamoytiiformes. It had an elongated body, and is thought to have had, in comparison with relatives known from intact bodies like Euphanerops, a dorsal fin and an anal fin near the rearmost third of its body. Earlier reconstructions depict the creature as having side-fins running the length of its body, starting from behind the branchial openings to the tip of its tail: new research demonstrates that such "fins" are actually deformations of the bodywall as the corpse was being squished post-burial.[2] In life, J. kerwoodi resembled a lamprey with a very small mouth. Because the fossil had no teeth, teeth-like structures, nor suggestions of either in its mouth, it was not carnivorous like many modern lampreys. It was more likely to have been a filter-feeder or a detritus-feeder, possibly in the manner of larval lampreys.

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

History of research

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,[2] its difficulty in classification due to difficulties in reconstructing the anatomy;[2] it does not possess any usual chordate synapomorphies. Currently, J. kerwoodi is now placed in its own order Jamoytiiformes, together with Euphanerops and similar agnathans.[2]

Further reading

  • 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

    References

    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. S2CID 86329654. Retrieved 2007-10-31.
    2. ^ a b c d 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.
    3. ^ Ritchie, A. (1968). (PDF). Palaeontology. 11: 21–39. Archived from the original (PDF) on 2011-07-16. 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. S2CID 129511577.
    5. ^ Dawkins, Richard The Ancestor's Tale
    6. ^ Ritchie, A. (1960). "A new interpretation of Jamoytius kerwoodi White". Nature. 188 (4751): 647. Bibcode:1960Natur.188..647R. doi:10.1038/188647a0. S2CID 4214197.


    jamoytius, kerwoodi, species, primitive, like, jawless, fish, that, lived, llandovery, epoch, early, silurian, period, temporal, range, llandovery, preꞒ, nscientific, classificationkingdom, animaliaphylum, chordataorder, jamoytiiformesfamily, jamoytiidaegenus,. Jamoytius kerwoodi was a species of primitive eel like jawless fish that lived in the Llandovery epoch of the Early Silurian period JamoytiusTemporal range Llandovery PreꞒ Ꞓ O S D C P T J K Pg NScientific classificationKingdom AnimaliaPhylum ChordataOrder JamoytiiformesFamily JamoytiidaeGenus JamoytiusSpecies J kerwoodiBinomial name Jamoytius kerwoodiWhite 1946 1 Long thought of as a basal anaspid J kerwoodi is now recognized as the best known member of the Hyperoartian order Jamoytiiformes It had an elongated body and is thought to have had in comparison with relatives known from intact bodies like Euphanerops a dorsal fin and an anal fin near the rearmost third of its body Earlier reconstructions depict the creature as having side fins running the length of its body starting from behind the branchial openings to the tip of its tail new research demonstrates that such fins are actually deformations of the bodywall as the corpse was being squished post burial 2 In life J kerwoodi resembled a lamprey with a very small mouth Because the fossil had no teeth teeth like structures nor suggestions of either in its mouth it was not carnivorous like many modern lampreys It was more likely to have been a filter feeder or a detritus feeder possibly in the manner of larval lampreys The fish had a cartilaginous skeleton and a branchial basket resembling the cyclostomes features that suggest that it was a basal member of that clade It is also the earliest known vertebrate with camera type eyes 3 It also possessed weakly mineralised scales 4 Contents 1 History of research 2 Further reading 3 Links to images 4 ReferencesHistory of research EditJamoytius 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 2 its difficulty in classification due to difficulties in reconstructing the anatomy 2 it does not possess any usual chordate synapomorphies Currently J kerwoodi is now placed in its own order Jamoytiiformes together with Euphanerops and similar agnathans 2 Further reading EditLong John A The Rise of Fishes 500 Million Years of Evolution Baltimore The Johns Hopkins University Press 1996 ISBN 0 8018 5438 5Links to images Edit 1 References Edit 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 S2CID 86329654 Retrieved 2007 10 31 a b c d 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 Ritchie A 1968 New evidence on Jamoytius kerwoodi White an important ostracoderm from the Silurian of Lanarkshire Scotland PDF Palaeontology 11 21 39 Archived from the original PDF on 2011 07 16 Retrieved 2007 10 31 Today G Blom Henning Marss Tiiu 2003 Fossils explained 43 Anaspid fishes Geology Today 19 3 111 113 doi 10 1046 j 1365 2451 2003 00413 x S2CID 129511577 Dawkins Richard The Ancestor s Tale Ritchie A 1960 A new interpretation of Jamoytius kerwoodi White Nature 188 4751 647 Bibcode 1960Natur 188 647R doi 10 1038 188647a0 S2CID 4214197 Paleontology portal This article about a prehistoric jawless fish is a stub You can help Wikipedia by expanding it vte This article related to a Silurian animal is a stub You can help Wikipedia by expanding it vte Retrieved from https en wikipedia org w index php title Jamoytius amp oldid 1103766033, wikipedia, wiki, book, books, library,

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