| 词条 | Pentameroceras |
| 释义 |
| name = Pentameroceras | fossil_range = M Silurian | image = | regnum = Animalia | phylum = Mollusca | classis = Cephalopoda | subclassis = Nautiloidea | ordo = Oncocerida | familia = Trimeroceratidae | genus = Pentameroceras | genus_authority = Hyatt, 1884 }} Pentameroceras is a straight to slightly exogastric breviconic oncocerid from the middle Silurian of North America and Europe belonging to the Trimeroceratidae. This nautiloid cephalopod produced a straight to slightly exogastric shell with a variable cross section that is generally circular, in which septa are close spaced and transverse, the body chamber is inflated. The aperture, which is constricted, consists of a narrow, vertical slit-like opening extending from the ventral hyponomic sinus to a dorsal sinus and two pairs of lateral sinuses that diverge in the upper portion. Siphuncles in the Trimeroceratidae are slender and empty. References
1 : Nautiloids |
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