Priscomyzon
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Priscomyzon Temporal range: Famennian
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holotype | |
Line drawing reconstruction | |
Scientific classification | |
Kingdom: | |
Phylum: | Chordata |
Class: | Hyperoartia |
Order: | |
Genus: | Priscomyzon Gess et al., 2006
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Type species | |
Priscomyzon riniensis Gess et al., 2006
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Priscomyzon riniensis is an extinct
Context
Though common and diverse during the Silurian and Devonian, jawless fish are today represented only by lampreys and hagfish, both groups being quite specialized. Lampreys have seven gill pouches (whereas jawed fish have only five), no paired fins, and a rudimentary skeleton of cartilage. They also have a sucker disc of cartilage surrounded by a soft lip and a central small mouth set about with simple hooked teeth. They attach to the bodies of other vertebrates by suction, securing their grip with the hooked teeth, after which a rasped tongue scrapes a hole providing access to the host's softer tissues.
Implications of the find
Priscomyzon provides evidence that agnathans close to modern lampreys had existed before the end of the
Description
The exceptionally well-preserved fossil of P. riniensis is only 42 millimetres (1.7 in) long and reveals details of its fin, gill basket and mouth region. A striking feature of Priscomyzon is its relatively large oral disk, inside a soft outer lip, supported by annular cartilage. The circular mouth at the center of the oral disk is surrounded by 14 small, evenly spaced, simple teeth, with no associated radiating series or plates of supplementary teeth, but otherwise quite similar to present-day lampreys, suggesting that their blood-sucking lifestyle was developed in ancient seas. The oral disk of the
Its posterior teeth are more elongate than the rest, while in modern species lateral or anterior teeth tend to be largest. Its teeth are also quite simple in shape compared to those of modern species, and in this respect are probably primitive. The position of the orbits is not clear as there are no darkened areas suggesting eye locations. The branchial imprint is preserved in great detail, parts of both the right and left baskets having been preserved, and the posterior five branchial arches being well defined. Anterior to these the presence of seven branchial pouches is evident. The dorsal fin originates immediately behind the branchiae and continues to the caudal extremity, resembling a modern ammocoete or lamprey larva rather than an adult, in which separate anterior and posterior dorsal fins are to be found.[2]
Fossils of juvenile specimens indicate that it did not have the filter feeding "ammocoete" juvenile stage found in modern lampreys, with juveniles morphologically similar to adults.[3]
Discovery
The lamprey fossil was discovered on
Etymology
The scientific name derives from the Latin
Holotype
The
See also
- Gondwanascorpio emzantsiensis
- Serenichthys kowiensis
References
- ^ "Discovery of the oldest fossil lamprey in the world" Archived 2013-02-13 at the Wayback Machine
- ^ S2CID 4302716.
- ISSN 0028-0836.
- Gess, Robert W.; Coates, Michael I.; Rubidge, Bruce S. (2006). "A lamprey from the Devonian period of South Africa". Nature. 443 (7114): 981–984. S2CID 4302716.