Cylostomiceratidae is a family of Early Ordovician, (Cassinian), ellesmerocerid cephalopods characterized by short, essentially straight shells, a fairly rapidly expanding phragmocone and a ventral siphuncle in which septal necks are almost non-existent and connecting rings are thick and layered. As typical of the Ellesmerocerida, chambers are short, septa close spaced.
Species taxanomy provided by GBIF Secretariat (2022). GBIF Backbone Taxonomy. Checklist dataset https://doi.org/10.15468/39omei accessed via GBIF.org on 2023-06-13; License: CC BY 4.0