Sigmocycloceras
Encyclopedia
Sigmocycloceras is a nautiloid cephalopod discovered in the Middle Ordovician of Korea, said to be similar to Sactorthoceras
, and included in the Sactorthoceratidae
, but unique in being longitudinally sigmoid and sculpted with transverse annuli.
Sactorthoceras
Sactorthceras is an orthoceratoid genus known from the Middle Ordovician of eastern North America , Norway and Korea and is the type genus of the Sactorthoceratidae....
, and included in the Sactorthoceratidae
Sactorthoceratidae
The Sactorthoceratidae comprise Orthocerataceaen genera with a subcentral suborthochoanitic siphuncle composed of slightly expanded segments and free of organic depsits...
, but unique in being longitudinally sigmoid and sculpted with transverse annuli.
References
- Walter C Sweet 1964. Nautiloidea-Orthocerida; Treatise on Invertebrate Paleontology, Part K. Geol Soc of America and Univ. Kansas Press.