Member species have a rather evolute shell in which the whorl section is more or less circular, venter broadly rounded and dorsum fairly deeply impressed. Close, fine low, single or rarely branching ribs are interspersed by frequent straight or slightly sinuous, moderately deep but wide constrictions. The type species S. rotulia is from the Hauterivian of England.[citation needed]
Biostratigraphic significance
The first appearance of the species Spitidiscus hugii or Spitidiscus vandeckii are proposed to be the marker for the beginning of the Barremian.[4]
^Wright, C. W. with Callomon, J.H. and Howarth, M.K. (1996), Mollusca 4 Revised , Cretaceous Ammonoidea, vol. 4, in Treatise on Invertebrate Paleontology, Part L (Roger L. Kaesler et al. eds.), Boulder, Colorado: The Geological Society of America & Lawrence, Kansas: University of Kansas Press, at 69.
^"Spitidiscus". Sepkoski's Online Genus Database – Cephalopoda.
^"GSSP Table - Mesozoic Era". Geologic Time Scale Foundation. Retrieved 15 January 2014.
Bibliography
"Spidiscus". Paleobiology Database. Retrieved 30 December 2021.
"Spidiscus". Encyclopedia of Life (EOL). Retrieved 30 December 2021.
Wright, Claud William; with John Hannes Callomon and M.K. Howarth (1996). Roger L. Kaesler (ed.). Mollusca 4 Revised, Cretaceous Ammonoidea in Treatise on Invertebrate Paleontology Part L. Boulder, Colorado and Lawrence, Kansas: The Geological Society of America & University of Kansas Press. p. 69.{{cite book}}: CS1 maint: multiple names: authors list (link)
Arkell, W. J.; Furnish, W. M.; Kummel, Bernhard; Miller, A.K.; Moore, R.C.; Schindewolf, O.H. (1957). "Part L, Mollusca 4: Cephalopoda, Ammonoidea". In Raymond C. Moore (ed.). Treatise on Invertebrate Paleontology. Geological Society of America and University of Kansas Press. p. L371. ISBN 978-0-8137-3012-7 – via Internet Archive.