Grammoceras

Grammoceras; Temporal range: Toarcian PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Mollusca
Class:	Cephalopoda
Subclass:	†Ammonoidea
Order:	†Ammonitida
Family:	†Hildoceratidae
Subfamily:	†Grammoceratinae
Genus:	†Grammoceras; Hyatt, 1867
Species
	Grammoceras striatulum (Sowerby, 1825); Grammoceras chateleti (De Brun, 1929); Grammoceras thouarsense (D'Orbigny, 1843); Grammoceras penestriatulum (Buckman, 1902); Grammoceras arenaceum (m) (Buckman, 1904); Grammoceras glabrum (m) (Monestier, 1921);

Grammoceras is an

extinct genus of ammonite found in Yorks Ravenscar, England, from Jurassic

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

^ Sepkoski, Jack (2002). "A compendium of fossil marine animal genera (Cephalopoda entry)". Bulletins of American Paleontology. 363: 1–560. Archived from the original on 2008-05-07. Retrieved 2017-10-18.

Arkell, W.J.; Kummel, B.; Wright, C.W. (1957). Mesozoic Ammonoidea. Treatise on Invertebrate Paleontology, Part L, Mollusca 4. Lawrence, Kansas: Geological Society of America and University of Kansas Press.

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