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 Historical, Architectural and Ethnographic Preservation Area. There are 89 wooden architectural monuments of the 15th to 20th centuries on the island. The most remarkable of those is Kizhi Pogost of the early 18th century which consists of a summer church with 22 domes, a winter church with nine domes, and a belfry. The pogost was included in the list of UNESCO World Heritage sites in 1990. In the summer, there are daily boat connections to the island from Petrozavodsk. Another attraction of the lake are the Onega petroglyphs (rock engravings). They are located on the eastern coast of the lake