Haikouichthys
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| Artist's concept of Haikouichthys ercaicunensis | |
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| Genus: | Haikouichthys
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Haikouichthys (pronounced hi-koo-ick-thees) is an extinct genus of craniate (creatures with backbones and distinct heads) believed to have lived c. 530 million years ago, during the Cambrian explosion. Haikouichthys had a defined skull and other characteristics that have led paleontologists to label it a true craniate, and even to be popularly characterized as one of the earliest fish,[1] but it does not possess sufficient features to be included uncontroversially even in the stem group.[2]
Description
Cladistic analysis indicates that the animal is probably a basal chordate, or a basal craniate.Cite error: The <ref> tag has too many names (see the help page). It is about 2.5 cm long and is narrower than Myllokunmingia, another putative chordate that comes from the same beds. The holotype was found in the Yuansshan member of the Qiongzhusi Formation in the 'Eoredlichia' Zone near Haikou at Ercaicun, Kunming City, Yunnan, China.[1]
The animal has a distinct head and tail. The head has at least six and perhaps nine probable gills. There are a number of segments (myomeres) with rear directed chevrons in the tail. There is probably a notochord, although only a short segment is preserved in the single known specimen. There is a prominent dorsal fin with fin radials similar, but not comparable, to those of hagfish and lampreys.[3] The fin radials seem to angle "forward" toward the end thought on the basis of internal structures to be the head. This happens with a few modern fish but is an uncommon arrangement. There are 13 circular structures along the bottom that may be gonads, slime organs, or something else entirely.
In Popular Culture
Haikouichthys was featured in the BBC documentary Walking with Monsters as the ancestor to all vertebrates.
See also
- Ostracoderm
- Arandaspis
- Pikaia Cambrian chordate
- Myllokunmingia close relative
- Zhongjianichthys eel-like close relative
External links
- See the following web sites for more information and pictures:
References
- ^ a b Attention: This template ({{cite doi}}) is deprecated. To cite the publication identified by doi:10.1038/nature01264, please use {{cite journal}} (if it was published in a bona fide academic journal, otherwise {{cite report}} with
|doi=10.1038/nature01264instead. - ^ Donoghue, P.C.J.; Purnell, M.A. (2005), "Genome duplication, extinction and vertebrate evolution" (PDF), Trends in Ecology & Evolution, 20 (6): 312–319, doi:10.1016/j.tree.2005.04.008, PMID 16701387
- ^ Zhang, X.G.; Hou, X.G. (2004), "Evidence for a single median fin-fold and tail in the Lower Cambrian vertebrate, Haikouichthys ercaicunensis", Journal of Evolutionary Biology, 17 (5): 1162–1166, doi:10.1111/j.1420-9101.2004.00741.x, PMID 15312089