Fuxianhuia
| Fuxianhuia Temporal range: LowerCambrian
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|---|---|
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| Fuxianhuia protensa | |
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| Fuxianhuia xiaoshibaensis | |
Scientific classification
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Order: | †Fuxianhuiida |
| Family: | †Fuxianhuiidae |
| Genus: | †Fuxianhuia Hou, 1987 |
| Type species | |
| Fuxianhuia protensa Hou, 1987
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| Other species | |
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Fuxianhuia xiaoshibaensisYang et al, 2013 | |
Fuxianhuiais a genus of LowerCambrianfossilarthropodknown from theChengjiang faunainChina.Its purportedly primitive features have led to its playing a pivotal role in discussions about theeuarthropodstem group.Nevertheless, despite being known from many specimens, disputes about its morphology, in particular its head appendages, have made it one of the most controversial of the Chengjiang taxa, and it has been discussed extensively in the context of thearthropod head problem.
The genus is named afterFuxian Lake(Fuxian Hu), where it was unearthed. Itsspecific nameprotensarefers to its extended trunk.[1]
Description
[edit]
CompleteFuxianhuiaspecimens are approximately 4 centimetres long. TheanteriorofFuxianhuiais encased in an ovalsclerite,from which two stalked eyes emerge. Inserting directly behind this sclerite, on the head shield proper, are two stout antennae. When the head ofFuxianhuiawas originally described, two additional head appendages, the "sub-chelate" pair were also described.[2]These aregeniculate,backward-pointingappendagesthat lie in a highly stereotypical position (i.e., their position does not vary much from one specimen to another). Partly because of this, and partly because of their rather indistinctmorphology,their status as appendages has been questioned. Indeed, on the grounds that these structures seem to lie between two cuticular layers, Waloszek and colleagues have suggested that they are not appendages at all, but rather gutdiverticula;[3]a reassignment that has however not been universally accepted.[4]Ventrally,a large plate has been interpreted as ahypostome.
The head shield overlaps a tapering series of 12–17 trunktergites,which lead into a set of limb-bearing segments comprising thethorax.The limbs are simple in form, consisting of a smooth ovalexopodand a stout, annulatedendopod.There is no one-to-one correspondence between the thoracic tergites and the limbs, but, rather, there appear to be two or three limbs pertergite.
Behind the thorax is a narrower abdominal region, consisting of 14 tergites, that bears no appendages. The abdomen is terminated by atelson-like spine.
Brain anatomy
[edit]In 2012, aFuxianhuiafossil was described with exceptional preservation of brain and optic lobes.[5]The shape and complexity corresponds roughly to that of a modernmalacostracanbrain.[5]In general, theFuxianhuiabrain shows the same tripartite morphology of Malacostraca,ChilopodaandInsecta,indicating that such an organization could be precedent to the divergence between these clades.[5]
Cardiovascular anatomy
[edit]In 2014 a fossil was described[6]that preserved in exquisite, unequaled detail the tubular heart and blood vessels, which represent the oldest cardiovascular system yet identified. "The rich vascularization in the head... suggests that the brain of this species required a good supply of oxygen for its performance," said University of Arizona neuroscientist Nicholas Strausfeld, one of the researchers.[7]
Classification
[edit]Fuxianhuiawas first described from incomplete material,[8]and its true nature did not become apparent until the head and limbs were discovered. Its articulated head region, lack of tergite-segment correspondence and undifferentiated limbs have all been taken to indicate a very basal position in the arthropods,[2][9][10]even though an early cladistic analysis suggested, rather, that it was a stem-groupchelicerate.[11]The presence of a distinct anterior sclerite bearing the eyes has been taken to suggest that a distinctacrononce existed in front of theeuarthropodhead.[2]
Fuxianhuiais not a unique arthropod, it is now recognised to belong to the cladeFuxianhuiidaincluding other similar forms from the Cambrian of China, within Fuxianhuiida it is most closely related toGuangweicaris,together forming the family Fuxianhuiidae. A cladogram is given below.
From.[12]
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References
[edit]- ^Dunham, Will."Sea creature fossil found with oldest-known cardiovascular system".Reuters.Archived fromthe originalon August 20, 2016.
- ^abcChen, JY; Edgecombe, G. D.; Ramsköld, L.; Zhou, L (1995). "Head segmentation in Early CambrianFuxianhuia:implications for arthropod evolution ".Science.268(5215): 1339–1343.Bibcode:1995Sci...268.1339C.doi:10.1126/science.268.5215.1339.PMID17778981.S2CID32142337.
- ^Waloszek, D.; Chen, J.; Maas, A.; Wang, X. (2005). "Early Cambrian arthropods – new insights into arthropod head and structural evolution".Arthropod Structure and Development.34(2): 189–205.doi:10.1016/j.asd.2005.01.005.
- ^Scholtz, G.; Edgecombe, G. D. (2006). "The evolution of arthropod heads: reconciling morphological, developmental and palaeontological evidence".Development, Genes and Evolution.216(7–8): 395–415.doi:10.1007/s00427-006-0085-4.PMID16816969.S2CID11300335.
- ^abcMa, X.; Hou, X.; Edgecombe, G. D.; Strausfeld, N. J. (2012). "Complex brain and optic lobes in an early Cambrian arthropod".Nature.490(7419): 258–261.Bibcode:2012Natur.490..258M.doi:10.1038/nature11495.PMID23060195.S2CID4408369.
- ^Ma X., Cong P., Hou X., Edgecombe G. D., Strausfeld N. J. (2014)."An exceptionally preserved arthropod cardiovascular system from the early Cambrian".Nature Communications.5:3560.Bibcode:2014NatCo...5.3560M.doi:10.1038/ncomms4560.PMID24704943.
{{cite journal}}:CS1 maint: multiple names: authors list (link) - ^Strausfeld, quoted inWill Dunham, "Sea creature fossil found with oldest-known cardiovascular system",Yahoo News,7 April 2014:accessed 7 April 2014.
- ^Hou, X.-g (1987). "Three New Large Arthropods from Lower Cambrian, Chengjiang, Eastern Yunnan [In Chinese]".Acta Palaeontologica Sinica.26:272–285.
- ^Hou, X.; Bergström, J. (1997). "Arthropods of the Lower Cambrian Chengjiang fauna, southwest China".Fossils & Strata.45:1–116.
- ^abBudd, G. E. (2002). "A Palaeontological Solution to the Arthropod Head Problem".Nature.417(6886): 271–275.Bibcode:2002Natur.417..271B.doi:10.1038/417271a.PMID12015599.S2CID4310080.
- ^Wills, M. A.; Edgecombe, G. D.; Ramsk ld, L. (1996)."Classification of the Arthropod".Science.272(5262): 746–747.doi:10.1126/science.272.5262.746.
- ^Yang, Jie; Ortega-Hernández, Javier; Legg, David A.; Lan, Tian; Hou, Jin-bo; Zhang, Xi-guang (2018-02-01)."Early Cambrian fuxianhuiids from China reveal origin of the gnathobasic protopodite in euarthropods".Nature Communications.9(1): 470.Bibcode:2018NatCo...9..470Y.doi:10.1038/s41467-017-02754-z.ISSN2041-1723.PMC5794847.PMID29391458.
Further reading
[edit]- Hou, Xian-Guang; Aldridge, Richard J., Bengstrom, Jan;Siveter, David J.;Feng, Xiang-Hong 2004; The Cambrian Fossils of Chengjang, China, Blackwell Science Ltd, 233 pp.