Ramskoeldia
| Ramskoeldia Temporal range:
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| Frontal appendages of R. platyacantha and R. consimilis | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Order: | †Radiodonta |
| Clade: | †Amplectobeluidae |
| Genus: | †Ramskoeldia Cong et al., 2018 |
| Type species | |
| Ramskoeldia platyacantha Cong et al., 2018
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| Species | |
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Ramskoeldia is a genus of amplectobeluid radiodont described in 2018. It was the second genus of radiodont found to possess gnathobase-like structures (abbreviated as GLS) and an atypical oral cone after Amplectobelua.[1] The type species, Ramskoeldia platyacantha, was discovered in the Chengjiang biota of China, the home of numerous radiodontids such as Amplectobelua and Lyrarapax.
Morphology
[edit]
Ramskoeldia is known only from a few frontal appendages, gnathobase-like structures (GLSs), disarticulated smooth and tuberculated plates interpreted as parts of their oral cones, as well as fragments of body flaps and head carapace complex.[1] The frontal appendage of Ramskoeldia is composed of 16 podomeres (3 shaft podomeres and 13 distal articulated region podomeres), with endites of podomeres 4 to at least podomere 12 bearing prominent auxiliary spines.[1] The endites of podomere 4 (first podomere of distal articulated region) is the largest compared to other endites, but not extremely enlarged like those of Amplectobelua.[1] The size of the endites alternates (those on even podomeres being larger than that of the odd podomere following it) and decreasing distally, except podomere 8 is larger than podomere 6 just like Amplectobelua. Compared to Amplectobelua, the GLSs of Ramskoeldia are wider and the three pairs of GLSs did not gradually alternate in size.[1]
Taxonomy
[edit]Two species of Ramskoeldia have been described, R. platyacantha and R.? consimilis, but the taxonomic placement of latter species within this genus has been consistently questioned by subsequent studies.[2][3][4] The endites of R. platyacantha are stout and their length does not exceed the height of the podomere to which they attach. The shaft podomeres 2 and 3 of R. platyacantha also bore prominent endites resembling those of distal articulated podomeres. Conversely, in R. consimilis, the endites of the distal articulated region are slender and most of them have a length that exceeds the height of podomere to which they attach. The shaft of R. consimilis has only a simple endite on podomere 3. The frontal appendages of R. consimilis had been previously misidentified as Houcaris saron owing to their similar overall appearance.[1]
Due to the numerous shared characters with Amplectobelua (e.g. larger endites of podomere 8; irregular oral cone; presence of GLSs), the discovery of Ramskoeldia questioned the amplectobeluid affinity of Lyrarapax, a presumed amplectobeliud genus which lacking characters noted above.[1] Ramskoeldia classified under Amplectobeluidae based on the diagnosis by Cong et al. 2018,[1] while further phylogenetic analysis either suggest it to be a member of Amplectobeluidae (alongside Amplectobelua, Lyrarapax, and Laminacaris)[5] or a relatively basal radiodont.[6]
References
[edit]- ^ a b c d e f g h Cong, Pei-Yun; Edgecombe, Gregory D.; Daley, Allison C.; Guo, Jin; Pates, Stephen; Hou, Xian-Guang (2018). "New radiodonts with gnathobase-like structures from the Cambrian Chengjiang biota and implications for the systematics of Radiodonta". Papers in Palaeontology. 4 (4): 605–621. Bibcode:2018PPal....4..605C. doi:10.1002/spp2.1219. ISSN 2056-2802. S2CID 90258934.
- ^ 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.
- ^ McCall, Christian (13 December 2023). "A large pelagic lobopodian from the Cambrian Pioche Shale of Nevada". Journal of Paleontology. 97 (5): 1009–1024. Bibcode:2023JPal...97.1009M. doi:10.1017/jpa.2023.63.
- ^ Wu, Yu; Pates, Stephen; Liu, Cong; Zhang, Mingjing; Lin, Weiliang; Ma, Jiaxin; Wu, Yuheng; Chai, Shu; Zhang, Xiangliang; Fu, Dongjing (16 July 2024). "A new radiodont from the lower Cambrian (Series 2 Stage 3) Chengjiang Lagerstätte, South China informs the evolution of feeding structures in radiodonts". Journal of Systematic Palaeontology. 22 (1). Bibcode:2024JSPal..2264887W. doi:10.1080/14772019.2024.2364887. hdl:10871/136118.
- ^ Lerosey-Aubril, Rudy; Pates, Stephen (2018-09-14). "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.
- ^ Moysiuk, J.; Caron, J.-B. (2019-08-14). "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). doi:10.1098/rspb.2019.1079. ISSN 0962-8452. PMC 6710600. PMID 31362637.
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