Strandoceras
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''Strandoceras'' is a strongly curved cyrtogomphoceratid with a laterally compressed cross section from the middle and upper
Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...
of
Northern Europe The northern region of Europe has several definitions. A restrictive definition may describe northern Europe as being roughly north of the southern coast of the Baltic Sea, which is about 54th parallel north, 54°N, or may be based on other ge ...
; Estonia, Norway, the U.K. The body chamber of ''Stradoceras'' is straighter and more slender than the chambered phragmocone; the venter narrowly rounded with a shallow hyponomic sinus; the aperture open, sutures with shallow lateral lobes. The siphuncle is close to the venter which is on the inside, endogastric curvature. Segments are large and broadly rounded; connecting rings thick, bullettes large. ''Strandoceras'' gave rise to the Phragmoceratidae and very likely to ''
Kiaeroceras ''Kiaeroceras'' is a slender, nearly straight shelled, cyrogomphoceratid (Nautiloidea-Discosorida Discosorida are an order of cephalopods that lived from the beginning of the Middle Ordovician, through the Silurian, and into the Devonian. Dis ...
'' and '' Cyrtogomphoceras'', which in turn gave rise to '' Landeroceras'', within the
Cyrtogomphoceratidae The Cyrtogomphoceratidae are a family in the cephalopod order Discosorida that comprises genera commonly with compressed, endogastrically curved shells. Siphuncles lie close to the ventral side, segments are broadly inflated, connecting rings th ...


References

* Flower, R H and Teichert, C; 1957. The Cephalopod Order Discosorida. University of Kansas Paleontological Contributions. Mollusca, Article 6, pp 1–144. * Teicher, C. 1964. Nautiloidea-Discosorida.
Treatise on Invertebrate Paleontology The ''Treatise on Invertebrate Paleontology,'' published from 1953–2007 by the Geological Society of America and the University of Kansas, then 2009–present by the University of Kansas Paleontological Institute, is a definitive multi-authore ...
, Part K. Teichert and Moore, eds. {{Taxonbar, from=Q7621294 Discosorida Prehistoric nautiloid genera Middle Ordovician first appearances Late Ordovician extinctions