Mollisonia
| Mollisonia Temporal range:
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|---|---|
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| Reconstruction of Mollisonia plenovenatrix | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Order: | †Mollisoniida |
| Family: | †Mollisoniidae |
| Genus: | †Mollisonia Walcott, 1912 |
| Type species | |
| †Mollisonia symmetrica Walcott, 1912
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| Species | |
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| Synonyms | |
|
Houghtonites Raymond, 1931 | |
Mollisonia is an extinct genus of Cambrian arthropod. 4 species had been described from North America and China. Studies suggest it is a basal member of Chelicerata, a group which includes horseshoe crabs and arachnids.[1][2]
Description
[edit]
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Reconstruction of Mollisonia plenovenatrix in lateral wiew
The genus is characterized by a capsule-like dorsal exoskeleton (tergites), which was divided into a subequal size of cephalon and pygidium with 7 thoracic segments in between. Below the cephalon was a pair of huge compound eyes, followed by a series of walking legs and gnathobasic (jaw-like) limbs, each have 3 pairs in total. As a Cambrian arthropod, the genus is significant by bearing several traits of now-surviving chelicerates, such as pincer-like mouthparts (chelicerae) and fused ring-like cephalic nerves (synganglion) within their head, as well as a series of multilayered book gills underneath their trunk appendages.[1][2]
Mollisonia may had been a benthic predator, using its anterior chelicerae and posterior gnathobasic limbs to devour prey items while using the 6 legs to walk around the sea floor. The gill-bearing trunk appendages may had been solely for breathing. This functional differentiation (head/prosomal appendages for feeding and walking, trunk/opisthosomal appendages for breathing) is closer to euchelicerates (crown-group chelicerates other than sea spiders) than the basal chelicerate genera of Habeliida (e.g. Habelia, Sanctacaris).[1]
Distribution and taxonomy
[edit]Three species (P. symmetrica, P. gracilis, P. plenovenatrix) are known from the Burgess Shale, with 21 specimens are known from the Greater Phyllopod bed, where they comprise less than 0.1% of the community as of 2006.[3] The genus is also known from Langston Formation, and Wheeler Shale of North America, as well as Chengjiang Biota of China (P. sinica).[4] Remains possibly attributable to the genus are also known from the Ordovician Fezouata Formation of Morocco and Bøggild Fjord Formation in Greenland.[5]
The taxonomic affinity of this genus was enigmatic until the discovery of its chelicerate features in 2019.[1] Subsequent studies suggest it is a basal chelicerate, closer to crown-group Euchelicerata than members of Habeliida. It is also suggested to be closely related to Corcorania, Urokodia (formerly[6]), and Thelxiope, which together form the order Mollisoniida.[1]
See also
[edit]References
[edit]- ^ a b c d e Aria, Cédric; Caron, Jean-Bernard (September 2019). "A middle Cambrian arthropod with chelicerae and proto-book gills". Nature. 573 (7775): 586–589. Bibcode:2019Natur.573..586A. doi:10.1038/s41586-019-1525-4. ISSN 0028-0836. PMID 31511691. S2CID 202550431.
- ^ a b Ortega-Hernández, Javier; Lerosey-Aubril, Rudy; Losso, Sarah R.; Weaver, James C. (2022-01-20). "Neuroanatomy in a middle Cambrian mollisoniid and the ancestral nervous system organization of chelicerates". Nature Communications. 13 (1): 410. doi:10.1038/s41467-022-28054-9. ISSN 2041-1723. PMC 8776822.
- ^ Caron, Jean-Bernard; Jackson, Donald A. (October 2006). "Taphonomy of the Greater Phyllopod Bed community, Burgess Shale". PALAIOS. 21 (5): 451–65. Bibcode:2006Palai..21..451C. doi:10.2110/palo.2003.P05-070R. JSTOR 20173022. S2CID 53646959.
- ^ Zhang, Xingliang; Zhao, Yuanlong; Yang, Ruidong; Shu, Degan (November 2002). "The Burgess Shale arthropod Mollisonia (M. sinica new species): new occurrence from the Middle Cambrian Kaili fauna of southwest China". Journal of Paleontology. 76 (6): 1106–1108. Bibcode:2002JPal...76.1106Z. doi:10.1017/S0022336000057917. ISSN 0022-3360. S2CID 130112985.
- ^ Peel, John S.; Willman, Sebastian; Pedersen, Stig A. Schack (March 2020). "Unusual preservation of an Ordovician (Floian) arthropod from Peary Land, North Greenland (Laurentia)". PalZ. 94 (1): 41–51. doi:10.1007/s12542-019-00481-y. ISSN 0031-0220.
- ^ Liu, Cong; Fu, Dongjing; Wu, Yu; Zhang, Xingliang (July 2024). "Cambrian euarthropod Urokodia aequalis sheds light on the origin of Artiopoda body plan". iScience: 110443. doi:10.1016/j.isci.2024.110443. PMC 11325232.
External links
[edit]- "Mollisonia symmetrica". Burgess Shale Fossil Gallery. Virtual Museum of Canada. 2011. Archived from the original on 2020-11-12.
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