Grammoceras
| Grammoceras Temporal range: Toarcian | |
|---|---|
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Mollusca |
| Class: | Cephalopoda |
| Subclass: | Ammonoidea |
| Order: | Ammonitida |
| Superfamily: | Hildocerataceae |
| Family: | Hildoceratidae |
| Subfamily: | Grammoceratinae |
| Genus: | Grammoceras Hyatt, 1867 |
| Species | |
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Grammoceras is an extinct ammonite found in Yorks Ravenscar, England, from Jurassic period sediments. Its overall distribution is fairly world wide.
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
- 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.