Siberion

Siberion is an extinct genus of lobopodian from the Sinsk biota of Russia. Its anatomy, including the proboscis-like organ projecting from the face and prominent grasping first pair of appendages, suggests that xenusians like this organism may have been phylogenetically related to anomalocaridids, like Anomalocaris.[1] Only two incomplete specimens are known, and the probability of finding more is low, as the Sinsk Algal Lens has been nearly destroyed by commercial fossil collectors.[1]

## Morphology

It is similar to other siberiids, however it is distinguished by the shape of its “tail” and body. The holotype preserves most of the body, however the appendages and head are incomplete. Its body is annulated, and while the head preserves large appendages and a radial mouth further details are unclear. Siberion has at least 12 pairs of legs which may have gill branches like other siberiids, however as mentioned previously they are incomplete. At the posterior end there is a bulbous structure, which is likely an extension of the body due to similar muscle impressions. The only internal structure seen is the digestive tract which resembles that of dinocaridids, however it is unclear whether gut diverticulae are present.[1]

## Phylogeny

Phylogeny of Panarthropoda after Knecht et al. 2025:[2]

†Diania 80px

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†Lenisambulatrix 80px

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†Paucipodia 80px

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†Thanahita 80px

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†Eoconchariidae

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†Microdictyon 80px

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†Fusuchoncharium

†Quadratapora

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†Xenusion 80px

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†Onychodictyon 80px

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†Strictocorniculum

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†Rhombocorniculum

†Orstenotubulus80px

†Carbotubulus

†Hallucigenia fortis

†Hallucigenia sparsa 80px

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†Hallucigenia hongmeia

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†Cardiodictyon 80px

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Tardigrada 80px

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†Luolishaniida

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†Ovatiovermis 60px

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†Facivermis 80px

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†Luolishania 80px

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†Collinsovermidae

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†Acincocricus

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†Collinsovermis 80px

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†Collinsium

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†Entothyreos 80px

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†Aysheaiidae

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†Aysheaia 80px

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†Hadranax 80px

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†Palaeocampa 80px

Antennopoda  |  |  |  |  |

†Antennacanthopodia 80px

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Onychophora (velvet worms) 80px

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†Siberiidae

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†Siberion 80px

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†Megadictyon 80px

†Jianshanopodia 80px

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†Pambdelurion 80px

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†Kerygmachelidae 80px

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†Opabiniidae 80px

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†Radiodonta (e.g. Anomalocaris) 80px

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Deuteropoda (modern arthropods) 100px

## References

1. ↑ 1.0 1.1 1.2 Dzik, Jerzy (July 1, 2011). "The xenusian-to-anomalocaridid transition within the lobopodians". Bollettino della Società Paleontologica Italiana 50 (1): 65-74. https://www.paleoitalia.it/wp-content/uploads/2024/07/07_Dzik_BSPI_Vol.50_Issue1.pdf. Retrieved 28 April 2025.
2. ↑ Knecht, Richard J.; McCall, Christian R. A.; Tsai, Cheng-Chia; Rabideau Childers, Richard A.; Yu, Nanfang (23 July 2025). "Palaeocampa anthrax, an armored freshwater lobopodian with chemical defenses from the Carboniferous". Communications Biology 8 (1). doi:10.1038/s42003-025-08483-0. PMID 40702124.

Template:Lobopodia Wikidata ☰ Q7507030 entry

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*[†]: Extinct