Biology:Cephalodiscus
| Cephalodiscus | |
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| Cephalodiscus dodecalophus | |
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| Family: | Harmer, 1905
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| Genus: | Cephalodiscus M'Intosh, 1882[1]
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| Type species | |
| Cephalodiscus dodecalophus McIntosh 1882
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Cephalodiscus is a genus of hemichordates in the monotypic family Cephalodiscidae of the order Cephalodiscida.
Description
All known species live in a secreted coenecium attached to a rock substrate.[2] Unlike Rhabdopleura, Cephalodiscus species do not form large colonies and are only pseudocolonial, but they do share a common area with individual buds for each zooid.[2][3] Cephalodiscus zooids are also more mobile than their Rhabdopleura counterparts, and are able to move around within tubaria. Cephalodiscus zooids can be produced via asexual budding. There are a few pairs of tentacled arms, whereas Rhabdopleura has only one pair of arms.[3]
Species
19 living species of Cephalodiscus have been described:[4]
- Cephalodiscus agglutinans Harmer & Ridewood, 1914
- Cephalodiscus atlanticus Bayer, 1962
- Cephalodiscus australiensis Johnston & Muirhead, 1951
- Cephalodiscus calciformis Emig, 1977
- Cephalodiscus densus Andersson 1907 [Cephalodiscus rarus Andersson, 1907; Cephalodiscus anderssoni Gravier 1912]
- Cephalodiscus dodecalophus McIntosh 1882
- Cephalodiscus evansi Ridewood
- Cephalodiscus fumosus John, 1932
- Cephalodiscus gilchristi Ridewood, 1908
- Cephalodiscus gracilis Harmer 1905
- Cephalodiscus graptolitoides Dilly 1993
- Cephalodiscus hodgsoni Ridewood, 1907 [Cephalodiscus aequatus Andersson 1907; Cephalodiscus inaequatus Andersson 1907]
- Cephalodiscus indicus Schepotieff 1909
- Cephalodiscus kempi John, 1932
- Cephalodiscus levinsoni Harmer 1905
- Cephalodiscus nigrescens Lankester 1905
- Cephalodiscus planitectus Miyamoto, Nishikawa and Namikawa, 2020
- Cephalodiscus sibogae Harmer 1905
- Cephalodiscus solidus Andersson, 1907
Extinct species include:
- †Cephalodiscus lutetianus Abrard, Dollfus & Soyer 1950
- †Cephalodiscus nusplingensis Schweigert & Dietl 2013
Proposed subgenera are idiothecia, demiothecia, orthoecus, and acoelothecia.[2]
Historical discovery
The Cephalodisci are endemic to the Antarctic and Southern Ocean, whose relative inaccessibility has historically limited human study of the genus.[2] The Erebus and Terror may have unwittingly encountered C. Nigrescens specimens, and the Challenger C. densus; but until the Swedish Antarctic Expedition of 1901-1903, only C. Dodecalphus had been identified.[5] In 1882, M'Intosh (later spelled McIntosh) had identified Dodecalphus from dredged Magellanic-Straits material, work published 5 years later, but the discovery left cephalodiscid phylogeny unclear.[2][5] M'Intosh proposed placement amongst the polyzoa, whilst Harmer suggested the modern placement amongst hemichordates. The Swedish expedition provided a plethora of new species, and subsequent researchers began to recognize cephalodiscid species in the relatively temperate waters off South Africa , the Falklands, Sri Lanka, and Australia . At the same time, researchers also determined that C. rarus and andersonii were in fact C. densus specimens.[2]
Cephalodiscus planitectus is the most recently discovered species. It was described in 2020 from specimens found in Sagami Bay off the southern coast of Honshu, Japan.[6]
References
- ↑ M'Intosh W (1882) Preliminary notice of Cephalodiscus, a new type allied to Prof. Allman's Rhabdopleura dredged in H.M.S. 'Challenger.'. Annals and Magazine of Natural History 10: 337-348
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Markham, John C. (1971). "The Species of Cephalodiscus collected during Operation Deep Freeze, 1956-1959". Biology of the Antarctic Seas. Antarctic Research. 17 (IV). Baltimore: Horn-Shafer. pp. 83-110. ISBN 0-87590-117-4. https://archive.org/details/biologyofantarct0000unse_r0w3/page/82/.
- ↑ 3.0 3.1 Maletz, Jörg (2017). Graptolite Paleobiology. Wiley-Blackwell. ISBN 9781118515617. https://www.wiley.com/en-us/Graptolite+Paleobiology-p-9781118515617.
- ↑ "Cephalodiscus". WoRMS. World Register of Marine Species. http://www.marinespecies.org/aphia.php?p=taxdetails&id=264904.
- ↑ 5.0 5.1 Ridewood, W. G. (October 1921). "On specimens of Cephalodiscus densus dredged by the ‘Challenger’ in 1874 at Kerguelen Island" (in en) (PDF). Annals and Magazine of Natural History 8 (46): 433–440. doi:10.1080/00222932108632603. ISSN 0374-5481. https://www.biodiversitylibrary.org/partpdf/63792.
- ↑ "Cephalodiscus planitectus sp. nov. (Hemichordata: Pterobranchia) from Sagami Bay, Japan". Zoological Science 37 (1): 79–90. February 2020. doi:10.2108/zs190010. PMID 32068377. https://bioone.org/journals/zoological-science/volume-37/issue-1/zs190010/Cephalodiscus-planitectus-sp-nov-Hemichordata--Pterobranchia-from-Sagami-Bay/10.2108/zs190010.short. Retrieved 2020-09-17.
External links
- "Cephalodiscus". WoRMS. World Register of Marine Species. http://www.marinespecies.org/aphia.php?p=taxdetails&id=264904.
Wikidata ☰ Q3830429 entry
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