''Jolietoceras'' is a compressed, annulate, lituiconic

nautiloid Nautiloids are a group of cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and ''Allonautilus''. Fossil nautiloids are diverse and species rich, with over 2,500 recorded species. Th ...

included in the derived Tarphycerid family,

Uranoceratidae The Uranoceratidae is a family of Silurian barrandeoceroids that tend to become uncoiled with age and in which siphuncle segments tend to be expanded into the camerae.Flower, R.H. & Kummel, B. 1950. A Classification of the Nautiloidea. Journal ...

. The shell is gyroconic in the early stage, becoming straight and more rapidly expanded in the later. sutures are straight and transverse. Surface annuli slope strongly to the rear, dorso-ventrally, in the early gyroconic stage but a lacking in the later straight segment. ''Jolietoceras'' comes from the Middle Silurian of the United States (Illinois, Wisconsin). The Uranoceratidae, ''including Jolietoceras'', were one included in the Barrandeocerida (Sweet, 1964), which has since been incorporated into the Tarphycerida.

References

* Sweet, W. C. 1964 Nautiloidea- Barrandeocerida.

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...

, Part K. Geol Soc of America and Univ of Kansas Press. Teichert & Moore, (eds) {{Taxonbar, from=Q16963208 Prehistoric nautiloid genera