Biology:Messorocaris
Messorocaris is a monotypic genus of fossil arthropod. The only known species is Messorocaris magna from the Wheeler Formation of Utah, dating back to the Cambrian (Drumian) period.[1][2]
Morphology
As of 2020, Messorocaris known only by two specimens. The holotype UU 17042.01 preserved the cephalon (head) and anterior half of the trunk.[1] The second specimen KUMIP312406 preserved only the trunk region, and was previously assigned to the similar-looking Dicranocaris.[3] It is a large arthropod, with a trunk measured up to 12 cm long.[2]
The body consists of a cephalic shield and a long, segmented trunk. All of the dorsal exoskeleton (tergite) have well-developed axial regions (vaulted middle sections) and tergopleurae (lateral extensions). The cephalic shield possess an anteriorly constricted axial region and wide pleural region, giving it a lens-shaped outline. The trunk has 12 body segments, divided by a series of overlapping tergites. The tergopleurae are somewhat reduced on the first segment, widely spaced and sickle-shaped at the second to fourth segments, increasingly recurved and narrower posteriorly from the fifth, and eventually become 3 pairs of posteriorly projecting spines at the last 3 segments. The telson (tail) elongated and narrow at the base, widen and bifurcate posteriorly.[2]
Appendages are only known by the partially preserved cephalic endopods. The anteriorly clustered position, terminal claws and posteriorly increased size resembling those of a sanctacaridid.[1]
Taxonomy
Based on the aforementioned similarity, Messorocaris is tentatively classified as a member of Habeliida (Sanctacarididae in the original description[1]), a group that increasingly evident to be a member of stem-group chelicerates.[4][5][6] Within putative habeliids, Dicranocaris might be a close relative of Messorocaris, differ by its semicircular cephalic shield and non sickle-shaped tergopleurae. Outside of habeliids, another similar-looking arthropod is Falcatamacaris (identified as an artiopod), particularly its sickle-shaped tergopleurae, but distinct by multiple features such as flatten cephalon, abrupt change of width between tergite 8–9 and calcitic exoskeleton.[2]
References
- ↑ 1.0 1.1 1.2 1.3 Lerosey-Aubril, Rudy; Skabelund, Jacob (2018). "Messorocaris, a new sanctacaridid-like arthropod from the middle Cambrian Wheeler Formation (Utah, USA)" (in en). Geological Magazine 155 (1): 181–186. doi:10.1017/S0016756817000504. ISSN 0016-7568. Bibcode: 2018GeoM..155..181L. https://www.researchgate.net/publication/317057763.
- ↑ 2.0 2.1 2.2 2.3 Lerosey-Aubril, Rudy; Kimmig, Julien; Pates, Stephen; Skabelund, Jacob; Weug, Andries; Ortega-Hernández, Javier (2020). Zhang, Xi-Guang. ed. "New exceptionally preserved panarthropods from the Drumian Wheeler Konservat-Lagerstätte of the House Range of Utah" (in en). Papers in Palaeontology 6 (4): 501–531. doi:10.1002/spp2.1307. ISSN 2056-2799. Bibcode: 2020PPal....6..501L. https://onlinelibrary.wiley.com/doi/10.1002/spp2.1307.
- ↑ Briggs, Derek E. G.; Lieberman, Bruce S.; Hendricks, Jonathan R.; Halgedahl, Susan L.; Jarrard, Richard D. (2008). "Middle Cambrian arthropods from Utah" (in en). Journal of Paleontology 82 (2): 238–254. doi:10.1666/06-086.1. ISSN 0022-3360. Bibcode: 2008JPal...82..238B. https://www.cambridge.org/core/journals/journal-of-paleontology/article/abs/middle-cambrian-arthropods-from-utah/B78C8E548B4E0BF042A1AAE08FD4725B.
- ↑ Aria, Cédric; Caron, Jean-Bernard (2017-12-21). "Mandibulate convergence in an armoured Cambrian stem chelicerate" (in en). BMC Evolutionary Biology 17 (1): 261. doi:10.1186/s12862-017-1088-7. ISSN 1471-2148. PMID 29262772. Bibcode: 2017BMCEE..17..261A.
- ↑ Aria, Cédric; Caron, Jean-Bernard (2019). "A middle Cambrian arthropod with chelicerae and proto-book gills" (in en). Nature 573 (7775): 586–589. doi:10.1038/s41586-019-1525-4. ISSN 1476-4687. PMID 31511691. Bibcode: 2019Natur.573..586A. https://www.nature.com/articles/s41586-019-1525-4.
- ↑ Lerosey-Aubril, Rudy; Ortega-Hernández, Javier (2026-04-01). "A chelicera-bearing arthropod reveals the Cambrian origin of chelicerates" (in en). Nature: 1–7. doi:10.1038/s41586-026-10284-2. ISSN 1476-4687. PMID 41922763. https://www.nature.com/articles/s41586-026-10284-2.
Wikidata ☰ Q139411276 entry
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