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Huronia is an actinocerid genus included in the Huroniidae along with Discoactinoceras and Huroniella,(Teichert 1964). Huronia is characterized by long siphuncle segments with the free part of the connecting rings only slightly inflated and by a narrow central canal and strongly curved radial canals located in the anterior part of each siphuncle segment
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.
Michelinoceras is the oldest known genus of the Michelinocerida, more commonly known as the Orthocerida, characterized by long, slender, nearly cylindrical orthocones with a circular cross section, long camerae, very long body chambers, and a central or near central tubular siphuncle free of organic deposits. Septal necks are straight; connecting rings cylindrical and thin. Cameral deposits are well developed. A radula has been found in one species, with seven teeth per row. It had ten arms, two of which formed longer tentacles.
Bathmoceras is a primitive cephalopod genus from the Middle and Upper Ordovician. It is a member of the order Cyrtocerinida and is the only genus in the family Bathmoceratidae.
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 Gasconadian Stage is the 1st stage of the Ordovician geologic period in North America and of the Lower Ordovician Canadian Epoch, coming immediately after the Late Cambrian Trempealeauan and preceding the middle Canadian Demingian Stage. The Gasconadian is equivalent to the European Tremadocian and roughly to the Skullrockian of the Ibexian series.
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.
Baltoceratidae is an extinct family of orthoconic cephalopods belonging to the subclass Nautiloidea endemic to what would be Asia, Australia, Europe, North America, and South America during the Ordovician living from about 480–460 mya, existing for approximately 20 million years.
The Actinoceriatidae are a family of actinocerids named by Saemann in 1853 for those that grew to have large shells with blunt apices and large siphuncles with widely expanded segments and a generally arcuate endosiphucular canal system. Their range is from the upper Middle Ordovician to the Lower Silurian. Actinocerids are generally straight-shelled nautiloid cephalopods with a siphuncle composed of expanded segments, typically with thin connecting rings, in which the internal deposits are penetrated by a system of canals
The Cassinian is the latest age of the Canadian Epoch when thought of temporally and the uppermost stage of the Canadian Series when thought of stratigraphically. The Canadian, either as a series or as an Epoch is the name that has been given to the Lower, or Early, Ordovician in North America and has been applied worldwide.
The Whiterockian, often referred to simply as the Whiterock, is an earliest or lowermost stage of the Middle Ordovician. Although the Whiterockian or Whiterock Stage refers mainly to the early Middle Ordovician in North America, it is often used in the older literature in a global sense.
The Jordan Formation is a siliciclastic sedimentary rock unit identified in Illinois, Michigan, Wisconsin, Minnesota, and Iowa. Named for distinctive outcrops in the Minnesota River Valley near the town of Jordan, it extends throughout the Iowa Shelf and eastward over the Wisconsin Arch and Lincoln anticline into the Michigan Basin.
The geology of Lithuania consists of ancient Proterozoic basement rock overlain by thick sequences of Paleozoic, Mesozoic and Cenozoic marine sedimentary rocks, with some oil reserves, abundant limestone, dolomite, phosphorite and glauconite. Lithuania is a country in the Baltic region of northern-eastern Europe.
The Owen Creek Formation is a stratigraphic unit of Middle Ordovician age. It is present on the western edge of the Western Canada Sedimentary Basin in the Canadian Rockies of Alberta and British Columbia. It consists primarily of dolomite and was named for Owen Creek near Mount Wilson in Banff National Park by B.S. Norford in 1969.
The Børglum River is a river in Peary Land, Greenland. It is the largest river in Greenland. Administratively it is part of the Northeast Greenland National Park.
The Knox Supergroup, also known as the Knox Group and the Knox Formation, is a widespread geologic group in the Southeastern United States. The age is from the Late Cambrian to the Early Ordovician. Predominantly, it is composed of carbonates, chiefly dolomite, with some limestone. There are also cherty inclusions as well as thin beds of sandstone.
References
- Flower, R.H. 1957; Flower, R.H. 1957, Studies of the Actinoceratida; Mem 2, New Mexico Bureau of Mines and Mineral Resources, Socorro, NM
- Flower, R.H. 1964;The Nautiloid Order Ellesmeroceratida (Cephalopoda);Memoir 12; New Mexico Bureau of Mines and Mineral Resources, Socorro, NM
- Moore Lalicker, and Fischer, 1952; Interbebrate Paleontology; McGraw-HIll;New York, Toronto, London.
- Weller,J.M 1960, Stratigraphic Principles and Practice, Harper's Geoscience Series, Harper and Brothers, New York.
(Geowhen: http://www.stratigraphy.org/geowhen/timelinestages.html )