Yorgiidae
From Wikipedia, the free encyclopedia
| Yorgiidae Temporal range: Ediacaran | |
|---|---|
 | |
| Fossil of the type species, Yorgia waggoneri | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | †Proarticulata |
| Class: | †Cephalozoa |
| Family: | †Yorgiidae Ivantsov, 2001 |
| Genera | |
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Yorgiidae is an extinct family of the class Cephalozoa, which is a part of the wider phylum Proarticulata.[1] They lived from around 571 to 551 Ma.
![](#/media/File:Photo_of_"Archaeaspinus_fedonkini"_fossil_Ivantsov_2007.png)
Like other relatives within the phylum Proarticulata, their body plan consists of isomers arranged in a glide symmetry, meaning they do not have true bilateral symmetry. As with other cephalozoans, their initial right isomer extends right across the body, forming a distinctive 'head', whilst they have a unique feature with their initial left isomer extending slightly to the right side and into the initial right isomer.
This is most prominent in the genus Archaeaspinus, with it having an unpaired left lobe/isomer within its 'head' region, forming a distinctive question mark-like shape.[1]
Distribution
Genera of the family Yorgiidae are most commonly found in the Ust' Pinega Formation and Central Urals of Russia,[1][2] as well as the Flinders Ranges of South Australia.[3]
