Superfamily Hildocerataceae Subfamily Grammoceratinae Rank Genus Subclass Ammonites | ||
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Similar Ammonites, Euhoplites, Euaspidoceras, Gleviceras, Hildoceras |
Grammoceras is an extinct ammonite found in Yorks Ravenscar, England, from Jurassic period sediments. Its overall distribution is fairly worldwide.

Grammoceras has a thin, discoidally evolute shell with simple, gently sigmoid ribbing and a low ventral keel. Dumortiera and Catulloceras from the same age are similar except that Dumortiera has a more rounded venter and Catulloceras has a subquadrate whorl section. Asthenoceras from the slightly younger lower Bajocian may be a subgenus.





References
Grammoceras Wikipedia(Text) CC BY-SA