Kerygmachela kierkegaardi is a kerygmachelid[2] gilled lobopodian from the Cambrian Stage 3 aged Sirius Passet Lagerstätte in northern Greenland. Its anatomy strongly suggests that it, along with its relative Pambdelurion whittingtoni, was a close relative of radiodont (Anomalocaris and relatives) and euarthropods.[3][1] The generic name "Kerygmachela" derives from the Greek words Kerygma (proclamation) and Chela (claw), in reference to the flamboyant frontal appendages. The specific name, "kierkegaardi" honors Danish philosopher Søren Kierkegaard.[3][1]
| Kerygmachela Temporal range:
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| Fossil of Kerygmachela kierkegaardi from the Sirius passet site | |
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| Reconstruction of Kerygmachela kierkegaardi based on later observations.[1] | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Family: | †Kerygmachelidae |
| Genus: | †Kerygmachela Budd, 1993 |
| Species: | †K. kierkegaardi
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| Binomial name | |
| †Kerygmachela kierkegaardi Budd, 1993
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Morphology
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The head of Kerygmachela possesses a pair of well-developed frontal appendages which correspond to those of other dinocaridids and siberiid lobopodians.[4] Each of them terminates in a series of long spines. A pair of sessile, slit-like compound eyes is located slightly behind the base of these appendages.[1] A small anterior-facing mouth is located below the head and bears a pair of stylet-like structures.[1] The head also possesses a median lobe-like projection that carries a pair of small, possible ocular structures (median eye).[1] The body is composed of 11 segments, each indicated by 4 dorsal turberculates associated with 11 pairs of lateral flaps with dorsal gill-like wrinkling.[3] Initially, 11 pairs of small legs (lobopods) were thought to be evident just below the flaps,[3] but later observations suggest the lopobods were most likely absent, and the flaps were originated from ancestral lopobods instead.[5][2] The body ends with a single, stiff tail spine[1][2] that was formerly thought to be a pair of segmented cerci.[3][6]
Internally, Kerygmachela possesses a well-developed pharynx[1] and a midgut with 8 pairs of arthropod-like digestive glands.[7] The brain have ramified nerves extended to the median lobe, frontal appendages and eyes.[1] Only the protocerebrum (the frontal-most cerebral ganglion) was evident from the brain region, thus all of the other head nerves were considered protocerebral.[1] On the other hand, a subsequent study of radiodont Stanleycaris might suggest a deutocerebral origin for the frontal appendage nerves.[8]
Paleoecology
editThe spiny frontal appendages suggests that Kerygmachela may have been a predator; however, fossils indicate a total size of approximately 175 mm and, with a relatively small mouth, suggest that it would have been restricted to very small prey.
References
edit- ^ a b c d e f g h i j Park, Tae-Yoon S.; Kihm, Ji-Hoon; Woo, Jusun; Park, Changkun; Lee, Won Young; Smith, M. Paul; Harper, David A. T.; Young, Fletcher; Nielsen, Arne T.; Vinther, Jakob (2018-03-09). "Brain and eyes of Kerygmachela reveal protocerebral ancestry of the panarthropod head". Nature Communications. 9 (1): 1019. doi:10.1038/s41467-018-03464-w. ISSN 2041-1723. PMC 5844904. PMID 29523785.
- ^ a b c McCall, Christian R. A. (2023-12-13). "A large pelagic lobopodian from the Cambrian Pioche Shale of Nevada". Journal of Paleontology: 1–16. doi:10.1017/jpa.2023.63. ISSN 0022-3360.
- ^ a b c d e Budd, Graham E. (1993), "A Cambrian gilled lobopod from Greenland", Nature, 364 (6439): 709–711, doi:10.1038/364709a0, S2CID 4341971
- ^ Ortega‐Hernández, Javier (2016). "Making sense of 'lower' and 'upper' stem-group Euarthropoda, with comments on the strict use of the name Arthropoda von Siebold, 1848". Biological Reviews. 91 (1): 255–273. doi:10.1111/brv.12168. ISSN 1469-185X. PMID 25528950. S2CID 7751936.
- ^ Lerosey‐Aubril, Rudy; Ortega‐Hernández, Javier (May 2022). Zhang, Xi‐Guang (ed.). "A new lobopodian from the middle Cambrian of Utah: did swimming body flaps convergently evolve in stem‐group arthropods?". Papers in Palaeontology. 8 (3). doi:10.1002/spp2.1450. ISSN 2056-2799.
- ^ Leanchoilia guts and the interpretation of three-dimensional structures in Burgess Shale-type fossils, Paleobiology
- ^ Vannier, Jean; Liu, Jianni; Lerosey-Aubril, Rudy; Vinther, Jakob; Daley, Allison C. (2014-05-02). "Sophisticated digestive systems in early arthropods". Nature Communications. 5 (1): 3641. doi:10.1038/ncomms4641. ISSN 2041-1723. PMID 24785191.
- ^ Moysiuk, Joseph; Caron, Jean-Bernard (2022). "A three-eyed radiodont with fossilized neuroanatomy informs the origin of the arthropod head and segmentation". Current Biology. 32 (15): 3302–3316.e2. doi:10.1016/j.cub.2022.06.027. ISSN 0960-9822.
Further reading
edit- Budd, G. E. (1999), "The morphology and phylogenetic significance of Kerygmachela kierkegaardi Budd (Buen Formation, Lower Cambrian, N Greenland)", Transactions of the Royal Society of Edinburgh, 89 (4): 249–290, doi:10.1017/S0263593300002418, S2CID 85645934
External links
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