Laminacaris

Laminacaris is a genus of extinct stem-group arthropods (Radiodonta) that lived during the Cambrian period. It is monotypic with a single species Laminacaris chimera, the fossil of which was described from the Chengjiang biota of China in 2018.[1] Around the same time, two specimens that were similar or of the same species were discovered at the Kinzers Formation in Pennsylvania, USA.[2] The first specimens from China were three frontal appendages, without the other body parts.

Laminacaris chimera
Temporal range:
Frontal appendage
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: †Dinocaridida
Order: †Radiodonta
Family: †Anomalocarididae
Genus: †Laminacaris
Guo et al., 2018
Species:
†L. chimera
Binomial name
†Laminacaris chimera
Guo et al., 2018

Discovery and naming

Laminacaris specimens were discovered from three sites in China: the mudstones of the Yu'anshan Member of the Chiungchussu Formation in eastern Yunnan Province, the Mafang section in the Haikou area at Kunming, and the Heimadi section, Chengjiang. The name is derived from Latin words, lamina meaning thin blade, and caris for crab; the species name refers to a Greek mythological creature, Chimera, that has a body composed of parts of more than one animal.[1]

Description
Laminacaris size diagram

The large frontal appendage is the most prominent and distinctive feature in Cambrian arthropods.[3][4] The frontal appendages of Laminacaris measure 11 cm (for the shortes specimen RCCBYU 10251) and 28 cm (for the longest but incomplete specimen YKLP 13338), and body length is estimated to be up to 78.4 cm, based on proportion of Innovatiocaris (which is once treated as "Anomalocaris" saron).[5] In many radiodonts and anomalocarids, the appendage is divided into segments called podomeres. Laminacaris's appendage has 15 podomeres, including 2 podomeres (podomeres 1 and 2) in the shaft and 13 (podomeres 3–15) in the distal articulated region.[1] The appendage bears several spines called endites on each lobomere. The biggest endite called shaft endite at the base (towards the body) is small and straight in most Cambrian arthropods, but is large, recurved and bears auxiliary spines in Laminacaris, Anomalocaris briggsi and Pahvantia hastata.[6]

Classification

A discovery of Burgess Shale radiodont Cambroraster falcatus in 2019 that was classified as member of the family Hurdiidae, led to the justification that Laminacaris could be the closest relative of and sister to Hurdiidae among the Radiodonta. Laminacaris may be a transitional form that diverged from the common ancestors.[7] Phylogenetic analysis based on the discovery of Pahvantia hastata, another member of Hurdiidae, shows that Laminacaris falls within the members of the family Anomalocaridae, next to Anomalocaris.[5] In 2022, it is treated that is possibly related to Innovatiocaris and Guanshancaris.[8]

References
  1. Guo, Jin; Pates, Stephen; Cong, Peiyun; Daley, Allison C.; Edgecombe, Gregory D.; Chen, Taimin; Hou, Xianguang (2019) [13 August 2018]. "A new radiodont (stem Euarthropoda) frontal appendage with a mosaic of characters from the Cambrian (Series 2 Stage 3) Chengjiang biota". Papers in Palaeontology. 5 (1): 99–110. doi:10.1002/spp2.1231. S2CID 134909330.
  2. Pates, Stephen; Daley, Allison C. (2019). "The Kinzers Formation (Pennsylvania, USA): the most diverse assemblage of Cambrian Stage 4 radiodonts". Geological Magazine. 156 (7): 1233–1246. Bibcode:2019GeoM..156.1233P. doi:10.1017/S0016756818000547. S2CID 134299859.
  3. Liu, Jianni; Dunlop, Jason A. (2014). "Cambrian lobopodians: A review of recent progress in our understanding of their morphology and evolution". Palaeogeography, Palaeoclimatology, Palaeoecology. 398: 4–15. Bibcode:2014PPP...398....4L. doi:10.1016/j.palaeo.2013.06.008.
  4. Giribet, Gonzalo; Edgecombe, Gregory D. (2019). "The Phylogeny and Evolutionary History of Arthropods". Current Biology. 29 (12): R592–R602. doi:10.1016/j.cub.2019.04.057. PMID 31211983. S2CID 189926344.
  5. Lerosey-Aubril, Rudy; Pates, Stephen (2018). "New suspension-feeding radiodont suggests evolution of microplanktivory in Cambrian macronekton". Nature Communications. 9 (1): 3774. Bibcode:2018NatCo...9.3774L. doi:10.1038/s41467-018-06229-7. ISSN 2041-1723. PMC 6138677. PMID 30218075.
  6. Pates, Stephen; Daley, Allison C.; Butterfield, Nicholas J. (2019). "First report of paired ventral endites in a hurdiid radiodont". Zoological Letters. 5 (1): 18. doi:10.1186/s40851-019-0132-4. PMC 6560863. PMID 31210962.
  7. Moysiuk, J.; Caron, J.-B. (2019). "A new hurdiid radiodont from the Burgess Shale evinces the exploitation of Cambrian infaunal food sources". Proceedings of the Royal Society B: Biological Sciences. 286 (1908): 20191079. doi:10.1098/rspb.2019.1079. ISSN 1471-2954. PMC 6710600. PMID 31362637.
  8. Zeng, Han; Zhao, Fangchen; Zhu, Maoyan (2022-09-07). "Innovatiocaris, a complete radiodont from the early Cambrian Chengjiang Lagerstätte and its implications for the phylogeny of Radiodonta". Journal of the Geological Society. 180. doi:10.1144/jgs2021-164. ISSN 0016-7649. S2CID 252147346.
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