Rhynchorthoceras
| Rhynchorthoceras Temporal range: MOrdovician
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| Genus: | Rhynchorthoceras
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Rhynchorthoceras is a Middle Ordovician genus characterized by a rapidly expanded, weakly annulate orthocone, like the orthoconic section of Ancistroceras, but with only a curved, cyrtoconic apex instead of juvenile whorls.
Rhynchorthoceras is probably derived from Ancistroceras by a loss of the tarphycerid type apex, although it has been included with the orthocerid Sinoceratidae.
References
[edit]- Flower, R. H. 1950. A Classification of the Nautiloidia. Jour Paleontology, V.24, N.5, pp 604–616, Sept.
- Furnish & Glenister, 1964. Nautiloidea -Tarphycerida. Treatise on Invertebrate Paleontology Part K, Mollusca 3 ...Nautiloidea