Yicaris dianensis is a species of microscopic pancrustacean[1][2] found in the Yu’anshan Formation, Yunnan Province, China.[3] Yicaris' discovery is notable because its age suggests that true crustaceans already existed as far back in time as Early Cambrian, much earlier than other fossils known from the Middle and Late Cambrian. Its closest living relatives are believed to be Cephalocaridans.[4]
| Yicaris Temporal range:
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| Artist's reconstruction of Yicaris dianensis | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Clade: | Pancrustacea |
| Genus: | †Yicaris Zhang et al., 2007 |
| Type species | |
| †Yicaris dianensis Zhang et al., 2007
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Etymology
editThe name Yicaris dianensis honors the ethnic minority Yi people of Yunnan Province, while Dian is an ancient kingdom of southern China. The suffix —caris refers to shrimp in Latin.[3]
Description
editYicaris' body consists of a cephalothorax covered by a head shield and limb-bearing segments.[3]
Out of the thirty-four specimens examined, six consecutive growth stages are known, the smallest one being 460 μm while the largest fossil, though fragmentary, reaches 1.8 mm long.[3]
Yicaris is also notable for the leaf-like structures on its limbs called epipodites. The developmental origin of epipodites is thought to be enigmatic, but Yicaris' discovery shows that early crustaceans already possessed a set of three epipodites on their limbs. This structure is considered important due to its potential significance in the evolution of wings in insects, which evolved from within Pancrustacea.[3]
References
edit- ^ Daley, Allison C.; Antcliffe, Jonathan B.; Drage, Harriet B.; Pates, Stephen (2018-05-22). "Early fossil record of Euarthropoda and the Cambrian Explosion". Proceedings of the National Academy of Sciences. 115 (21): 5323–5331. Bibcode:2018PNAS..115.5323D. doi:10.1073/pnas.1719962115. PMC 6003487. PMID 29784780.
- ^ "Early Crustacean Evolution and the Appearance of Epipods/Gills". ResearchGate. Retrieved 2020-11-04.
- ^ a b c d e Zhang, Xi-guang; Siveter, David; Waloszek, Dieter; Maas, Andreas (4 October 2007). "An epipodite-bearing crown-group crustacean from the Lower Cambrian". Nature. 449 (7162): 595–598. Bibcode:2007Natur.449..595Z. doi:10.1038/nature06138. PMID 17914395. S2CID 4329196.
- ^ Wolfe, Joanna M.; Hegna, Thomas A. (2014). "Testing the phylogenetic position of Cambrian pancrustacean larval fossils by coding ontogenetic stages". Cladistics. 30 (4): 366–390. doi:10.1111/cla.12051. ISSN 1096-0031. PMID 34788971. S2CID 86382575.
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