| 词条 | Rhynchorthoceras |
| 释义 |
| name = Rhynchorthoceras | fossil_range = MOrdovician | image = | regnum = Animalia | phylum = Mollusca | classis = Cephalopoda | subclassis = Nautiloidea | ordo = Tarphycerida | familia = Lituitidae | genus = Rhynchorthoceras | genus_authority = }} 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
2 : Nautiloids|Paleozoic life of Newfoundland and Labrador |
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