''Involuticeras'' is a perisphinctoid

ammonite Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) ...

belonging to the Aulacostephanininae from the

Upper Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 163.5 ± 1.0 to 145.0 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

of Europe and possibly Mexico. The shell is involute, moderately compressed, with a rounded and ribbed venter. The genus is similar in general form to ''

Aulacostephanus ''Aulacostephanus'' is an extinct ammonoid cephalopod genus from the Upper Jurassic Tithonian belonging to the perisphinctoidean family Aulacostephanidae. ''Aulacostephanus'' produced a discoidal, strongly ribbed, evolute shell of moderate s ...

'' and ''

Epicephalites ''Epicephalites'' is a perisphictid ammonite, included in the subfamily Aulacostephaninae, from the Upper Jurassic of New Zealand and Mexico, related to '' Involuticeras''. Its shell is involute, whorls inflated with a deep umbilicus. The outer h ...

''.

References

Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology'' (or ''TIP'') published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 paleontologists, and co ...

, Part L,(1957), Mesozoic Ammonoidea, p. L324. Jurassic ammonites Ammonitida genera Perisphinctidae Ammonites of Europe {{ammonitina-stub