Cephalozoa

Cephalozoa[1] are an extinct class of primitive segmented marine organisms within the Phylum Proarticulata from the Ediacaran period. They possessed bilateral symmetry and were characterized by a thin, rounded body.

## Contents

* 1 Description
* 2 Taxonomy
* 2.1 Yorgiidae
* 2.2 Sprigginidae
* 3 See also
* 4 References

## Description

Yorgia waggoneri organization diagram.

Unlike the other classes of proarticulates, the segmentation of the body is not complete and shows a "head" with fine distribution channels. Some species of the Yorgiidae family also show some asymmetry.[2][3][4]

They were discovered in Russia near the White Sea in the Arkhangelsk region, where they lived during the Ediacaran, approximately 635 to 540 Ma (millions of years ago).

## Taxonomy

Cephalozoa includes the families Yorgiidae and Sprigginidae, as well as genera not assigned to any family:

### Yorgiidae

* † Archaeaspinus Ivantsov, 2007 (synonym of Archaeaspis)
* † Archaeaspinus fedonkini Ivantsov, 2001
* † Yorgia Ivantsov, 1999
* † Yorgia waggoneri Ivantsov, 1999
* † Ivovicia Ivantsov, 2007
* † Ivovicia rugulosa Ivantsov, 2007

### Sprigginidae

* † Spriggina Glaessner, 1958
* † Spriggina floundersi Glaessner, 1958
* † Spriggina ovata Glaessner and Wade, 1966 now considered synonym of Marywadea ovata.
* † Marywadea Glaessner, 1976
* † Marywadea ovata Glaessner and Wade, 1966
* † Cyanorus Ivantsov, 2004
* † Cyanorus singularis Ivantsov, 2004
* † Praecambridium Glaessner and Wade, 1966, previously classified as Yorgiidae; now considered a juvenile form of Spriggina[5]
* † Praecambridium sigillum Glaessner and Wade, 1966

Fossil of Andiva ivantsovi.

The genera Cephalonega,Andiva, Lossinia and Podolimirus are also included in Cephalozoa, although are not part of any family:[6]

* † Cephalonega Fedonkin in Ivantsov et al., 2019
* † Cephalonega stepanovi Fedonkin, 1976
* † Andiva Fedonkin, 2002
* † Andiva ivantsovi Fedonkin, 2002
* † Lossinia Ivantsov, 2007
* † Lossinia lissetskii Ivantsov, 2007
* † Podolimirus Fedonkin, 1983
* † Podolimirus mirus Fedonkin, 1983

Recent studies indicate that the family Yorgiidae could be included or closely related to the class Vendiamorpha.[7]

## See also

* Ediacaran fauna

## References

1. ↑ Ivantsov, A. Y. (2001). "Vendia and Other Precambrian "Arthropods"" (in en). Paleontological Journal 35 (4): 335–343. https://www.academia.edu/2605872.
2. ↑ Ivantsov, A. Yu (2004). "New Proarticulata from the Vendian of the Arkhangel'sk Region" (in en). Paleontological Journal 38 (3): 247–253. http://vend.paleo.ru/pub/Ivantsov_2004_eng.pdf.
3. ↑ Ivantsov, A. Y.; Malakhovskaya, Y. E.; Serezhnikova, E. A. (2004). "Some Problematic Fossils from the Vendian of the Southeastern White Sea Region" (in en). Paleontological Journal 38 (1): 1–9. http://www.vend.paleo.ru/pub/Ivantsov_et_al_2004_eng.pdf. Retrieved 2021-08-11.
4. ↑ Ivantsov, A. Y. (2004). Vendian Animals in the Phylum Proarticulata (PDF) (Thesis). Prato, Italy: The Rise and Fall of the Vendian Biota. IGSP Project 493. Abstracts. p. 52.
5. ↑ Ivantsov, Andrey Yu (2007). "Small Vendian transversely Articulated fossils" (in en). Paleontological Journal 41 (2): 113–122. doi:10.1134/S0031030107020013. Bibcode: 2007PalJ...41..113I. https://www.academia.edu/2352394.
6. ↑ Ivantsov, A. Yu.; Fedonkin, M. A.; Nagovitsyn, A. L.; Zakrevskaya, M. A. (September 2019). "Cephalonega, A New Generic Name, and the System of Vendian Proarticulata". Paleontological Journal 53 (5): 447–454. doi:10.1134/S0031030119050046.
7. ↑ Vendiamorpha at fossilworks.org

Template:Proarticulata Wikidata ☰ Q30750018 entry

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