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.

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.

[3][4][5] 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).