Nectocaris pteryx is a species of possible cephalopod known from the "early Cambrian" Emu Bay Shale and Chengjiang biota, the "middle Cambrian" Burgess Shale.
Plectronocerida is a primitive order from which subsequent cephalopod orders are ultimately derived.
The Ellesmerocerida is an order of primitive cephalopods belonging to the subclass Nautiloidea with a widespread distribution that lived during the Late Cambrian and Ordovician.
Ectenolites is a genus of small, slender, cylindrical Ellesmeroceratids that resemble Ellesmeroceras but are smaller and proportionally narrower. Septa, as typical for ellesmerocerids, are close spaced with shallow lobes on either flank. The body chamber is proportionally long, the shell itself slightly compressed. The dorsal side at the beginning of the shell, opposite the aperture and body chamber, is strongly convex so to produce a sense of endogastric curvature with the apex and siphuncle aligned.
Clarkoceras is a genus of breviconic ellesmerocerid cephalopods, one of only two genera known to have crossed from the Late Cambrian, Trempealeauan, into the Early Ordovician, Gasconadian. ; the other being Ectenolites.
The end-Botomian mass extinction event, also known as the late early Cambrian extinctions, refer to two extinction intervals that occurred during Stages 4 and 5 of the Cambrian Period, approximately 513 to 509 million years ago. Estimates for the decline in global diversity over these events range from 50% of marine genera up to 80%. Among the organisms affected by this event were the small shelly fossils, archaeocyathids, trilobites, brachiopods, hyoliths, and mollusks.
Palaeophragmodictya is an extinct genus of sponge-grade organisms from the Ediacaran Period. Originally interpreted as a hexactinellid sponge, the organism also bears some coelomate characteristics, including bilateral symmetry.
The Actinocerida are an order of generally straight, medium to large cephalopods that lived during the early and middle Paleozoic, distinguished by a siphuncle composed of expanded segments that extend into the adjacent chambers, in which deposits formed within contain a system of radial canals and a narrow space along the inner side of the connecting ring known as a paraspatium. Septal necks are generally short and cyrtochoanitic, some being recumbent, some hook shaped. Most grew to lengths of about 60 to 90 cm but some, like the Huroniidae of the Silurian grew significantly larger.
The Dresbachian is a Maentwrogian regional stage of North America, lasting from 501 to 497 million years ago. It is part of the Upper Cambrian and is defined by four trilobite zones. It overlaps with the ICS-stages Guzhangian, Paibian and the lowest Jiangshanian.
The Ellesmeroceratidae constitute a family within the cephalopod order Ellesmerocerida. They lived from the Upper Cambrian to the Lower Ordovician. They are characterized by straight and endogastric shells, often laterally compressed, so the dorso-ventral dimension is slightly greater than the lateral, with close spaced sutures having shallow lateral lobes and a generally large tubular ventro-marginal siphuncle with concave segments and irregularly spaced diaphragms. Connecting rings are thick and layered, externally straight but thickening inwardly with the maximum near the middle of the segment so as to leave concave depressions on internal siphuncle molds. Septal necks are typically orthochoanitic but vary in length from almost absent (achoanitic) to reaching halfway to the previous septum (hemichoanitic) and may even slope inwardly (loxochoanitic).
The Trempealeauan is the upper or latest stage of the Upper or Late Cambrian in North America, spanning about 4 million years from about 492.5 to 488.3 m.y.a., equivalent to the Fengshanian of China. The name comes from the Trempealeau Formation, named for the town of Trempealeau in western Wisconsin, located on the Mississippi River.
The Franconian is the middle stage of the Upper or Late Cambrian in North America, equivalent to the Chinese Changshanian with a span of nearly 4.5 million years, from about 497 to 492.5 Ma. The name comes from the Franconia Formation, about 100 feet of sandstone and green shale exposed near the town of Franconia in eastern Minnesota, north of St Paul.
The cephalopods have a long geological history, with the first nautiloids found in late Cambrian strata, and purported stem-group representatives present in the earliest Cambrian lagerstätten.
Plectronoceratoidea is a superorder of primitive nautiloids from the Late Cambrian and Early Ordovician that include the ancestors of subsequent cephalopod orders. Included within are the exclusively Cambrian Plectronocerida, Protactinocerida, and Yanhecentida, and the Cambro-Ordovician Ellesmerocerida.
Paraplectronoceras is a genus of very early nautiloids from the middle Late Cambrian, named by Chen and Qi, 1979, type species Paraplectronoceras pyriforme, for small, endogastrically curved forms found in the upper Yenchou and Wanwankou members of the Fengshan Formation of northeastern China.
Shungtangenoceras is a conical plectronoceratoid cephalopod from the Upper Cambrian of north-eastern China, described by Sun (1937) as a primitive endoceroid. Because of its apparently poor preservation its ordinal and familial position is uncertain. It could be included in either the Plectronocerida, family Plectronoceratidae, or the Ellesmerocerida, family Ellesmeroceratidae. On the other hand, Teichert (1964) included Shungtangendoceras in the Ellesmoerocatidae.
Paleoceras is a genus of fossil cephalopods from the Upper Cambrian.
Acaroceratidae is family of Upper Cambrian (Trempealeauan) nautiloid cephalopods included in the Ellesmerocerida that contains two known genera, Acaroceras and Weishanuceras, both found in northern China.
Eburoceras is an early nautiloid cephalopod from the Upper Yenchau and Wanwankau, Upper Cambrian Trempealeauan of China, assigned to the Ellesmeroceratidae.
Huaiheceras is a genus of ellesmerocerd from China, and type for the Heuhiceratidae that lived during the Late Cambrian. The shell is small, tubular, gently expanding and with a slight curvature. The siphuncle, which is proportionally narrow, is on the outer, concave curvature of the shell, suggesting it is exogastric. Septa are close spaced.
