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Siberion Temporal range: Early Cambrian 518–513 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Reconstruction of Siberion lenaicus
Scientific classification
Kingdom:	Animalia
Phylum:	Lobopodia
Class:	†Xenusia
Order:	†Siberiida
Family:	†Siberiidae
Genus:	†Siberion Dzik 2011
Species:	†S. lenaicus
Binomial name
†Siberion lenaicus Dzik 2011

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. Only one incomplete specimen is known, and the probability of finding more is low, as the Sinsk Algal Lens has been nearly destroyed by fossil poachers.

Morphology

It is similar to other siberiids, however it is distinguished by the shape of its “tail” and body. The only specimen 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.

References

1. Gradstein, Felix; Ogg, James; Smith, Alan (2004). A Geologic Time Scale. Cambridge University Press. pp. 147–149. ISBN 0-521-78673-8.
2. Ivantsova, Andrey; Zhuravlevb, Andrey; Legutaa, Anton; Valentin, Krassilova; Melnikovaa, Lyudmila; Ushatinskayaa, Galina (2005). "Palaeoecology of the Early Cambrian Sinsk biota from the Siberian Platform" (PDF). Palaeogeography, Palaeoclimatology, Palaeoecology. 220 (1–2): 69–88. doi:10.1016/j.palaeo.2004.01.022.
3. ^ Dzik, Jerzy (2011). "The xenusian-to-anomalocaridid transition within the lobopodians". Bollettino della Società Paleontologica Italiana, 50(1): 65-74.

• Xenusia
• Lobopodia
• Cambrian genus extinctions