original descriptionStokes Ch. (1840). On some species of Orthocerata. <em>Transactions of the Geological Society of London, series 2.</em> 5: 705-714., available online athttps://www.biodiversitylibrary.org/page/36235981 page(s): 709 [details]
additional sourceKröger, B. (2025). The Lyckholm acme of cephalopods – Review of the late Katian (Vormsi–Pirgu regional stages) Ordovician cephalopods of Estonia. <em>European Journal of Taxonomy.</em> 978: 1-169., available online athttps://doi.org/10.5852/ejt.2025.978.2801 page(s): 19 [details] Available for editors [request]