Kerygmachela
Extinct gilled lobopod
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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 radiodonts (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  | |
| Kingdom: | Animalia |
| Stem group: | Arthropoda |
| Class: | †Dinocaridida |
| Family: | †Kerygmachelidae |
| Genus: | †Kerygmachela Budd, 1993 |
| Species: | †K. kierkegaardi |
| Binomial name | |
| †Kerygmachela kierkegaardi Budd, 1993 | |
Morphology
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
Phylogeny
After McCall 2023:[2]
| Total group Euarthropoda |
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