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Kerygmachela Temporal range: Cambrian Stage 3 PreꞒ Ꞓ O S D C P T J K Pg N
Fossil of Kerygmachela kierkegaardi from the Sirius passet site
Reconstruction of Kerygmachela kierkegaardi based on later observations.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Family:	†Kerygmachelidae
Genus:	†Kerygmachela Budd, 1993
Species:	†K. kierkegaardi
Binomial name
†Kerygmachela kierkegaardi Budd, 1993

Kerygmachela kierkegaardi is a kerygmachelid 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. 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.

Morphology

The head of Kerygmachela possesses a pair of well-developed frontal appendages which correspond to those of other dinocaridids and siberiid lobopodians. 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. A small anterior-facing mouth is located below the head and bears a pair of stylet-like structures. The head also possesses a median lobe-like projection that carries a pair of small, possible ocular structures (median eye). 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. Initially, 11 pairs of small legs (lobopods) were thought to be evident just below the flaps, but later observations suggest the lopobods were most likely absent, and the flaps were originated from ancestral lopobods instead. The body ends with a single, stiff tail spine that was formerly thought to be a pair of segmented cerci.

Internally, Kerygmachela possesses a well-developed pharynx and a midgut with 8 pairs of arthropod-like digestive glands. The brain have ramified nerves extended to the median lobe, frontal appendages and eyes. Only the protocerebrum (the frontal-most cerebral ganglion) was evident from the brain region, thus all of the other head nerves were considered protocerebral. On the other hand, a subsequent study of radiodont Stanleycaris might suggest a deutocerebral origin for the frontal appendage nerves.

Paleoecology

The 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

1. ^ 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. Bibcode:2018NatCo...9.1019P. doi:10.1038/s41467-018-03464-w. ISSN 2041-1723. PMC 5844904. PMID 29523785.
2. ^ McCall, Christian R. A. (2023-12-13). "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. ISSN 0022-3360.
3. ^ Budd, Graham E. (1993), "A Cambrian gilled lobopod from Greenland", Nature, 364 (6439): 709–711, Bibcode:1993Natur.364..709B, doi:10.1038/364709a0, S2CID 4341971
4. 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.
5. 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). Bibcode:2022PPal....8E1450L. doi:10.1002/spp2.1450. ISSN 2056-2799.
6. Leanchoilia guts and the interpretation of three-dimensional structures in Burgess Shale-type fossils, Paleobiology
7. 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. Bibcode:2014NatCo...5.3641V. doi:10.1038/ncomms4641. ISSN 2041-1723. PMID 24785191.
8. 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. Bibcode:2022CBio...32E3302M. doi:10.1016/j.cub.2022.06.027. ISSN 0960-9822. PMID 35809569.

Further reading

• 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

• Anomalocarid Homepage
• Palaeos -

v t e Dinocaridida
Kingdom: Animalia Superphylum: Ecdysozoa Clade: Panarthropoda Phylum: Stem-group Arthropoda
Dinocaridida	Caryosyntrips ?Parvibellus Omnidens Pambdelurion Youti Kerygmachelidae Kerygmachela Utahnax Mobulavermis Opabiniidae Opabinia Utaurora Mieridduryn Radiodonta see Radiodonta
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• Dinocaridida
• Prehistoric arthropod genera
• Cambrian arthropods
• Cambrian Greenland
• Fossils of Greenland
• Sirius Passet fossils
• Buen Formation
• Fossil taxa described in 1993
• Søren Kierkegaard
• Cambrian genus extinctions
• Prehistoric arthropod stubs