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Charactoceras
''Charactoceras'' is a tarphycerid genus cephalopod which lived during the Late Ordovician.
''Charactoceras'' has a closely coiled, rapidly expanding evolute shell, dorsally impressed, with a flattened venter and rounded sides. Sutures are close spaced laterally, but with broad ventral and dorsal lobes. Hyponomic sinus is well developed. The siphuncle is cyrtochoanitic and empty, located between the center and venter; segments expanded slightly into the chambers.
The genus ''Charactocerina'' from the Late Orovician is similar but has costae on the dorsolateral region of the shell. Both are included in the family Aspidoceratidae. Also somewhat similar to ''Charactoceras'' in external form are ''Uranoceras'' and ''Cumingsoceras'' from the Middle Silurian, but both differ in detail.
==References==
Walter C. Sweet, 1964. Nautiloidea- Barrandeocerida; Treatise on Invertebrate Paleontology. Geological Society of America and University of Kansas Press.
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