Mollisonia

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Mollisonia
Temporal range: Cambrian Stage 3–Floian
20190922 Mollisonia plenovenatrix.png
Reconstruction of Mollisonia plenovenatrix
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Chelicerata
Order:† Mollisoniida
Family:† Mollisoniidae
Genus:† Mollisonia
Walcott, 1912
Type species
†Mollisonia symmetrica
Walcott, 1912
Species
  • †Mollisonia gracilisWalcott, 1912
  • †Mollisonia plenovenatrixAria and Caron, 2019
  • †Mollisonia sinicaZhang et al., 2002
  • †Mollisonia symmetricaWalcott, 1912
Synonyms

Houghtonites Raymond, 1931

Mollisonia is an extinct genus of Cambrian arthropod. 4 species have 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]

Contents

Description

Mollisonia symmetrica in various views showing digestive (cyan) and nervous systems (purple) 41467 2022 28054 Fig4 HTML.png
Mollisonia symmetrica in various views showing digestive (cyan) and nervous systems (purple)

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 have 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 have 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

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

References

  1. 1 2 3 4 5 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.
  2. 1 2 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. Bibcode:2022NatCo..13..410O. doi:10.1038/s41467-022-28054-9. ISSN   2041-1723. PMC   8776822 . PMID   35058474.
  3. ↑ 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.
  4. ↑ 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.
  5. ↑ 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. Bibcode:2020PalZ...94...41P. doi: 10.1007/s12542-019-00481-y . ISSN   0031-0220.
  6. ↑ Liu, Cong; Fu, Dongjing; Wu, Yu; Zhang, Xingliang (July 2024). "Cambrian euarthropod Urokodia aequalis sheds light on the origin of Artiopoda body plan". iScience. 27 (8): 110443. Bibcode:2024iSci...27k0443L. doi: 10.1016/j.isci.2024.110443 . PMC   11325232 . PMID   39148713.
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