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Williamsoceras
Williamsoceras is an endocerid that Rousseau Flower (1968) added to his Allotrioceratidae (Flower 1955) on the basis of having a vertical partition within the siphuncle, known as a ventral process, with inter-connecting tubule-like structures along its margin where intercepted by endocones. Three species are named and described (Flower 1968) from the Garden City limestone of Whiterockian age near Logan and northern Utah, including the genotype ''Williamsoceras adnatum''. Two other species come from the Juab limestone (Flower 1976) of near equivalent age in the southern Confusion Range in the Ibex area in western Utah. Description Of the five described species the siphuncle wall and phragmocone are known only from the genotype ''Williamsoceras adnatum''. The other four are known only from pieces of siphuncle which show only internal configurations, but closely resemble that of the genotype. ''Williamsoceras'' is characterized by a ventral process within the siphuncle that e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Allotrioceratidae
The Allotrioceratidae is a family of Middle Ordovician fossils, established by Rousseau Flower, 1955, originally including ''Allotrioceras'' and '' Mirabilocras'', assigned inferentially to the Endocerida and known only from structures interpreted as siphuncles. Later ''Williamsoceras'', '' Cacheoceras'', and '' Perkinsoceras'' (Flower 1968, 1976) were added. Similar ''Allotrioceras'' and ''Mirabiloceras'', known only from the Chazyan (upper lower Middle Ordovician) of New York, are tubular organisms with complex interiors somewhat resembling that of the Endocerida. The later added ''Williamsoceras'', ''Cacheoceras'', and ''Perkinsoceras'' are true endocerids as indicated by their cylindroid shells, phragmocones, and siphuncles. ''Williamsoceras'' and ''Cacheoceras'' are from the Whiterockian stage (lower lower Middle Ordovian) of Utah. ''Perkinsoceras'', which appeared somewhat later, is from the Chazyan of New York, like ''Allotrioceras'' and ''Mirabilioceras'' but rather di ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Perkinsoceras
''Perkinsoceras''is an endocerid genus from the Middle Ordovician (Chazyan) of Champlain Valley established by Flower in 1976, which he added to his Allotrioceratidae based on certain similarities to ''Williamsoceras'' and '' Cacheoceras'' which had been added previously. ''Perkinsoceras'' is characterized by a large ventral siphuncle in broad contact with the ventral margin of the phragmocone -the chambered portion of the shell- which is expanded into a '' Nanno'' type apex, and by a broad longitudinal ventral process about which the endocones are draped. ''Perkinsoceras'' has what have been interpreted as tubules that form where the endocones impinge on the process, a feature also interpreted in ''Williamsoceras'', ''Cacheoceras'' and the distinctly unique ''Allotrioceras ''Allotrioceras'' is a tubular fossil from the Middle Ordovician of the state of New York, collected by Rousseau H. Flower; included by him in the Endocerida and placed in a new family, the Allotriocerat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ordovician
The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. The Ordovician, named after the Celtic Britons, Welsh tribe of the Ordovices, was defined by Charles Lapworth in 1879 to resolve a dispute between followers of Adam Sedgwick and Roderick Murchison, who were placing the same Rock (geology), rock beds in North Wales in the Cambrian and Silurian systems, respectively. Lapworth recognized that the fossil fauna in the disputed Stratum, strata were different from those of either the Cambrian or the Silurian systems, and placed them in a system of their own. The Ordovician received international approval in 1960 (forty years after Lapworth's death), when it was adopted as an official period of the Paleozoic Era by the International Union of Geological Sciences, Intern ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phragmocone
The phragmocone is the chambered portion of the shell of a cephalopod. It is divided by septa into camerae. In most nautiloids and ammonoids, the phragmocone is a long, straight, curved, or coiled structure, in which the camarae are linked by a siphuncle which determines buoyancy by means of gas exchange. Despite this benefit, such a large shell adds to the mass of the animal, and hence is disadvantageous in catching fast-moving prey. Some nautiloids, such as the Silurian Ascocerida, dropped the phragmocone upon maturity, presumably to increase speed and maneuverability. They thus became the early Paleozoic equivalent of coleoids. The early coleoids and belemnoids adopted a different approach: the phragmocone was retained but became internal and reduced. In general the shell in cephalopods tends to be vestigial or absent. Fossil record Being the only biomineralised part of most cephalopods, the phragmocone is typically the only part to enter the fossil record. It is somet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Proterocameroceratidae
The ''Proterocameroceratidae'' were the first of the Endocerida. They began early in the Ordovician with ''Proendoceras'' or similar genus which had developed endocones, replacing the diaphragms of the ellesmerocerid ancestor. Proterocameroceratids are long, straight or gently curved with a generally narrow siphuncle along the ventral margin. Septal necks are short, never quite reaching the previous septum and may vary in length ontogenically within a species. Connecting rings are thick and layered. Endocones are simple, especially in early forms but may be complex with secondary structures in later forms. The Proterocameroceratidae gave rise to the Piloceratidae early on, and later to the Manchuroceratidae and Chihlioceratidae, from which the Allotrioceratidae are derived, and later yet possibly to the Emmonsoceratidae and Najaceratidae. The Piloceratidae in turn may have given rise to the Endoceratidae although a proterocameroceratid ancestor remains possible. Proterocamerocer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Canadian Epoch
The Canadian is the Lower or Early Ordovician in North America. The term is common in the older literature and has been well understood for more than a century. However it has no official recognition by the International Commission on Stratigraphy (ICS) and has been superseded by the more recently defined Ibexian series of western Utah. Background Dana introduced the Canadian as the name for a system separated from the rest of the Ordovician (Weller 1980), then known as the Lower Silurian, and referred to the rest of the Lower Silurian as the Trenton System. At that time the Ordovician had not yet been recognized. Later Ulrich redefined the Canadian as roughly equivalent to the Beekmantown strata of the Lower Ordovician. Flower (1957 p. 17) felt that recognition of the Canadian as a separate system would greatly solve problems in Early Paleozoic stratigraphy. As such, faunas in limestones of Canadian age are uniformly widespread and set off sharply from black shale graptolite ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Champlain Valley
The Champlain Valley is a region of the United States around Lake Champlain in Vermont and New York extending north slightly into Quebec, Canada. It is part of the St. Lawrence River drainage basin, drained northward by the Richelieu River into the St. Lawrence at Sorel-Tracy, Quebec (northeast of Montreal). The Richelieu valley is not generally referred to as part of the Champlain Valley. The Champlain Lake Valley is the most heavily populated region in Vermont, broadly stretching eastward from the lake's shore to the base of the Green Mountains. The state's largest city, Burlington, is located on the lake, and the city's associated suburban communities encompass part of the central section of the valley. Beyond urbanized Chittenden County, however, the valley's landscape is primarily open pasture and row crops, making the Champlain Valley the most productive agricultural region of Vermont. The New York portion of the Champlain Valley includes the eastern portions of Clinton ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
