Kerygmachela Temporal range:
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Fossil of Kerygmachela kierkegaardi from the Sirius passet site | |
Reconstruction of Kerygmachela kierkegaardi based on later observations. [1] | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Arthropoda |
Class: | † Dinocaridida |
Family: | † Kerygmachelidae |
Genus: | †
Kerygmachela Budd, 1993 |
Species: | †K. kierkegaardi
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Binomial name | |
†Kerygmachela kierkegaardi Budd, 1993
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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 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]
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]
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.
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The Cambrian explosion |
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