4-399: Adamsoceras Cyrtonybyoceras Wutinoceras The Wutinoceratidae are a family of early actinocerids defined by Shimazu and Obata in 1938 for actinocerids with thick connecting rings and a complex irregular canal system. Actinocerids are generally straight shelled nautiloid cephalopods with a siphuncle composed of expanded segments, typically with thin connecting rings, in which
8-521: Is slightly broader than high, i.e. depressed, with close spaced septa that form ventral lobes and a siphuncle that is near the ventral margin. Adamsoceras is known from rocks of Whiterockian age (early Middle Ordovician ) in Nevada, the Baltic, Tasmania, and Manchuria. It may have been derived from Wutinoceras , or from a common ancestor, and gave rise to Ormoceras . The genotype is Adamsoceras isabelae from
12-543: The Ormoceratidae . Wutinoceras , further on, gave rise to the Armenoceratidae and possibly to the immediate ancestors of Actinoceras . Adamsoceras Adamsoceras is a genus of actinocerids of the family Wutinoceratidae , with spheroidal siphuncle segments like Ormoceras , but having a reticular canal system like Wutinoceras . Adamsoceras has a slender, gently expanding, orthoconic shell that
16-541: The internal deposits are penetrated by a system of canals. The Wutinoceratidae include three genera, Wutinoceras , Cyrtonybyoceras , and Adamsoceras , known especially from the early Middle Ordovician (Whiterock stage) in northeastern China and North America, but found also from the same age in Australia and northern Europe. Wutinoceras is the earliest and gave rise to Cyrtonybyoceras and Adamsoceras . Cyrtonybyoceras left no descendants, but Adamsoceras gave rise to
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