Grammoceras
Genus of ammonite
From Wikipedia, the free encyclopedia
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  | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | †Ammonoidea |
| Order: | †Ammonitida |
| Family: | †Hildoceratidae |
| Subfamily: | †Grammoceratinae |
| Genus: | †Grammoceras Hyatt, 1867 |
| Species | |
| |
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.
