Grammoceras

Grammoceras is an extinct genus of ammonite found in Yorks Ravenscar, England, from Jurassic period sediments. Its overall distribution is fairly worldwide.

Grammoceras
Temporal range:
Scientific classification Edit this 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 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
  1. 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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