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Grammoceras

Grammoceras Temporal range: Toarcian[1] 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 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.

• 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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