Onega stepanovi placed in phylum Proarticulata, as the segments in recently discovered, exceptionally well-preserved fossils display the glide, or "staggered", symmetry characteristic of the majority of proarticulatans. Imprints of "Onega stepanovi" have been found in the Verkhovka and Zimnie Gory Formations of the Ediacaran (Vendian) rocks of the Arkhangelsk Region, Russia. All the fossil specimens are negative imprints on the bases of fine-grained sandstone beds with the "elephant skin" and tubercle texture diagnostic of microbial mats. The same bedding planes contain various other Ediacaran species: "Cyclomedusa", "Ediacaria", palaeopascichnids, "Eoporpita", "Yorgia", "Andiva", "Archaeaspinus", "Vendia", "Dickinsonia", "Anfesta", "Albumares", "Tribrachidium", "Kimberella", "Parvancorina", "Charniodiscus" and others.
Lake Onega a total area of about . Whereas the most famous is Kizhi, which contains historical wooden churches of the 18th century, the largest island is Big Klimenetsky with an area of . It contains a few settlements, a school and an hill. Other large islands are Big Lelikovsky and Suysari. The lake banks are low and are flooded with raising water level. They are therefore swampy and are rich in reed, hosting ducks, geese and swans. The coastal region is covered with dense virgin forests. Major tree types are coniferous, but also common are lime (linden), elm and European alder.