Yorgia

Yorgia (reconstruction )

• Flinders Ranges, Australia
• White Sea, Russia
• Ural, Russia

• Yorgia waggoneri

Yorgia is a genus of extinct creatures. Your currently the only known representative, Yorgia waggoneri, lived in the Ediacaran before 555 million years ago and is difficult to compare with today's living creatures. Its fossils are similar to those of Dickinsonia. The systematic classification of Yorgia is controversial because of the numerous often unique and therefore difficult to interpret features of fossils. In general Yorgia is regarded as an early representative of multicellular animals ( Metazoa ).

Features

Fossil finds of Yorgia show a resemblance to those of Dickinsonia and furthermore also Spriggina. Yorgia was up to 23 cm long. In comparison with the oval to Dickinsonia almost circular body was relatively thick and had a flat top and bottom. The body was divided into segments or chambers. The Body of Yorgia follows no exact bilateral symmetry. So shows the the " head segment " following the first " body segment " a significant asymmetry. Additional depressions on the surface of Fossil footprints were interpreted as evidence for organs, possibly gonads.

Way of life

Fossil traces give few clues to the lifestyle of Yorgia. It is believed that Yorgia be a mechanism of food intake served, which is now used only by representatives of the tribe of Placozoa. Probably grazed Yorgia on the seabed over lawn of microorganisms digested this externally and took them on with the help of the entire ventral surface. Alternatively, an autotrophic way of life is discussed, after which Yorgia used the symbiosis with unicellular algae or in situ chemoautotrophic bacteria for energy supply.

Trace fossils indicate an active or at least passive locomotion.

System

The systematic classification of Yorgia is problematic due to the difficult -to-interpret features and the largely absence of similarity to current living organisms and is therefore controversially discussed in the literature. In general, the genus of the realm of multicellular animals ( Metazoa ) is assigned. The describer Andrei Ivantsov arranged Yorgia the group of Proarticulata, a hypothetical tribe extinct predecessor of today's two- page animals ( Bilateria ), too. Due to the segmentation of an assignment to the core group of arthropods is discussed.

However, the striking differences of the body structure of a bilateral symmetry provide additional opportunities for interpretation. Adolf Seilacher arranged Yorgia to the extinct Vendobionten, which he interpreted as a large chambered unicellular organisms. Also, a relationship with the animal strain Placozoa was discussed.

Discovery history

Yorgia was discovered in the late 1990s by Andrei Ivantsov in an annual expedition to the coast of the White Sea in Russia's Arkhangelsk County and described in 1999 for the first time scientifically. The name of the genus derives from locality near the river Jorga. The type species Yorgia waggoneri was named in honor of paleontologist Ben Waggoner.