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 in its center. Thawing starts in April in the tributaries and reaches the lake in May. Water in the deep parts is clear, with the visibility up to . In the bays, the visibility may decrease to about a meter. The water is fresh, with a salinity of 35 mg/L. This is relatively low for a lake and is about times lower than in the other large lake of the area, Lake Ladoga. The maximum surface water temperature is on the open lake and in the bays. The deep waters are much colder, from in winter to in summer. Weather