Yorgia

Yorgia waggoneri Temporal range: Ediacaran
Fossil of Yorgia waggoneri
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	†Proarticulata
Class:	†Cephalozoa
Family:	†Yorgiidae
Genus:	†Yorgia Ivantsov, 1999
Species:	†Y. waggoneri
Binomial name
†Yorgia waggoneri Ivantsov, 1999[1]

Yorgia waggoneri is a discoid

Etymology

The generic name Yorgia comes from the Yorga river on the Zimnii Bereg (Winter Coast) of the White Sea, where the first specimens were found. The specific name Yorgia waggoneri honors the American paleontologist Ben Waggoner, who found the first specimen.

Morphology

The body plan of the Yorgia and other proarticulates is unusual for solitary (non-colonial) metazoans. These bilateral organisms have segmented metameric bodies, but left and right transverse elements (

The integument of the dorsal side were unsegmented and covered with small tubercles, same as with

[6]

Fossil record

Imprints of the species Yorgia waggoneri have been found in the rocks of

of Russia ^[8] and Flinders Ranges, Australia.^[9] Most body imprints of Yorgia have in the past been primarily preserved on the sole of sandstone beds in negative relief. Other Yorgia fossils show internal structure in the original organism, showing two symmetrical rows of nodules, a central tube, rib-like tubes, and a semicircular shape with a hole in the circle centre positioned towards the head end. This structure has been interpreted as the impression of gonads, intestine and mouth.^[10]

Trace fossils

cilia, located on the ventral side of the body, which caught and transported particles of the food substrate into the special elongated pockets arranged on the borders between the isomers.^[11] Chevron-like marks on the positive imprints have been taken as evidence of this cilia activity.^[3][12] This feeding habit is unknown in post-Ediacaran deposits.^[13]

Taphonomic details revealed in Yorgia allow interpretation of the chains of positive imprints of other proarticulates as grazing traces, as opposed to trails created as organisms were swept along the sea floor by currents. In addition to Yorgia, two fossil taxa, Epibaion and Phyllozoon, seem to have produced similar grazing traces. Small groups of positive body imprints are documented for Dickinsonia costata as well and Dickinsonia cf. tenuis.^[12][14]

See also

• List of Ediacaran genera

References

1. ^ Ivantsov, A.Y. (1999). "A New Dickinsonid from the Upper Vendian of the White Sea Winter Coast (Russia, Arkhangelsk Region)". Paleontological Journal. 33 (3): 233–241.
2. ^ ^{a b} Ivantsov, A.Y. (2001). "Vendia and Other Precambrian "Arthropods"". Paleontological Journal. 35 (4): 335–343.
3. ^ ^{a b} Ivantsov, A.Y. (2004) "Vendian Animals in the Phylum Proarticulata". The Rise and Fall of the Vendian Biota. IGSP Project 493. Abstracts. Prato, Italy, p. 52.
4. S2CID 89131248
   .
5. ^ Ivantsov, A. Yu.; Zakrevskaya, M. A.; Nagovitsyn, A. L. (2018). "Morphology of the covers of Proarticulata (Ediacaran Metazoa)" (PDF). Ist Palaeontological Virtual Congress. Book of Abstracts.: 65.
6. doi:10.15298/invertzool.16.1.03
   .
7. doi:10.1080/08912969909386585
   . Retrieved 29 January 2023.
8. ^ Grazhdankin, D. V.; Maslov, A. V., Mustill, T. M. R.; Krupenin, M. T. (2005). "The Ediacaran White Sea Biota in the Central Urals". Doklady Earth Sciences. 401 (6): 784–788.{{cite journal}}: CS1 maint: multiple names: authors list (link)
9. doi:10.1016/j.palaeo.2005.12.015
   .
10. PMID 21680416
    .
11. S2CID 55178329
    .
12. ^ ^{a b} Ivantsov, A.Y.; Malakhovskaya, Y.E. (2002). "Giant Traces of Vendian Animals" (PDF). Doklady Earth Sciences. 385 (6): 618–622.
13. S2CID 128741869
    .
14. S2CID 17181699
    .