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Actinocerida
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. (Teichert 1964) Septal necks are generally short and cyrtochoanitic, some being recumbent, some hook shaped. Most grew to lengths of about but some, like the Huroniidae of the Silurian grew significantly larger. Ecology The Actinocerida inhabited shallow to quite deep waters, where they alternated between swimming and lying on the bottom. They were predatory, and able to control their buoyancy to a greater degree than their contemporaries. Derivation The derivation of the Actinocerida remains enigmatic. They first appear late in the Early Ordovician (Cassinian Stage, late Floian) with the Georginida ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cephalopods
A cephalopod is any member of the molluscan class Cephalopoda (Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. Fishers sometimes call cephalopods "inkfish", referring to their common ability to squirt ink. The study of cephalopods is a branch of malacology known as teuthology. Cephalopods became dominant during the Ordovician period, represented by primitive nautiloids. The class now contains two, only distantly related, extant subclasses: Coleoidea, which includes octopuses, squid, and cuttlefish; and Nautiloidea, represented by ''Nautilus'' and ''Allonautilus''. In the Coleoidea, the molluscan shell has been internalized or is absent, whereas in the Nautiloidea, the external shell remains. About 800 living species of cephalopods have been identified. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nautiloid
Nautiloids are a group of marine cephalopods (Mollusca) which originated in the Late Cambrian and are represented today by the living ''Nautilus'' and '' Allonautilus''. Fossil nautiloids are diverse and speciose, with over 2,500 recorded species. They flourished during the early Paleozoic era, when they constituted the main predatory animals. Early in their evolution, nautiloids developed an extraordinary diversity of shell shapes, including coiled morphologies and giant straight-shelled forms (orthocones). Only a handful of rare coiled species, the nautiluses, survive to the present day. In a broad sense, "nautiloid" refers to a major cephalopod subclass or collection of subclasses (Nautiloidea ''sensu lato''). Nautiloids are typically considered one of three main groups of cephalopods, along with the extinct ammonoids (ammonites) and living coleoids (such as squid, octopus, and kin). While ammonoids and coleoids are monophyletic clades with exclusive ancestor-descendant re ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wutinoceras
''Wutinoceras'' is a genus of now extinct nautiloid cephalopods of the Wutinoceratidae family. It exhibits orthoconic actinocerids with ventral siphuncles composed of broadly expanded segments.Memoir 2, Studies of the Actinocerida, New Mexico Bureau of Mines and Mineral ResourcesMemoir 19, The First Great Expansion of the Actinoceroids, New Mexico Bureau of Mines and Mineral Resources Distinguishing characteristics ''Wutinoceras'', as with its family the Wutinoceratidae, has a reticulated canal system within the siphuncle, distinguishing it from later forms with arcuate canal systems. Septal necks, components of the siphuncle that project from the back side of the septa, are cyrtochoanitic (outwardly curved) and may be recumbent. Connecting rings are thick, reflective of the ancestral form. Varieties The three varieties of ''Wutinoceras'' are based on the form of the siphuncle, and each contains a number of species. These have not been ascribed to subgenera. They include th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Huronia (cephalopod)
''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 Ancestry Teichert, (1964) indicated ''Huronia'' as being derived from the upper Middle Ordovician ''Discoactinoceras'', whose ancestry lay in the direction of ''Polydesmia'', once considered the prototypical actinocerid. Flower, (1968) on the other hand, showed that ''Huronia'' is derived from '' Actinoceras'' and split off from '' Lambeoceras'' during Red River time, near the start of the Late Ordovician, precluding the inclusion of ''Discoactinoceras'' Distribution ''Huronia'' is known from the Upper Ordovician and Silurian of North America and Greenland. ''H. arctica'' and ''H occidentalis''(?) are associa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Armenoceratidae
The Armenoceratidae are a family of early Paleozoic nautiloid cephalopods belonging to the order Actinocerida.Flower 1957.Studies of the Actinoceratida.; Memoir 2; New Mexico Bureau of Mines and Mineral Resources, Socorro, NM Teichert 1964. Actinoceratoidea, Treatise on Invertebrate Paleontology, part K.(Nautiloidea) The Armenoceratidae, established by Troedsson (1926) are characterized by large, straight, or slightly curved shells and large siphuncles with strongly expanded segments between the septa. Septal necks are short and abruptly recurved along brims. Radial canals in the endosiphuncular canal system are typically arched, curving forward and backward from near the septal foramina (openings) to connect with the parispatium on either side of the middle of each segments. The parispatium is the narrow opening between the inner side of the connecting rings in actinocerids and the internal siphuncular deposits that grow forward and back from the region of the septal open ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lambeoceratidae
''Lambeoceras'' is a genus of large actinocerids with a convexly lenticular cross section from the Upper Ordovician of North America and the sole representative of the family Lambeoceratidae. Morphological description ''Lambeoceras'' is of medium to moderately large size with a long, straight, depressed shell, broad in cross section with the dorsum and venter both about equally convex, meeting acutely along the sides. Chambers are short, and septa are closely spaced, forming broad lobes on the upper and lower sides, which meet in sharp saddles along the sides. The siphuncle is submarginal, near the ventral side and relatively narrow. Septal necks are extremely long, brims short and recumbent. Segments are broadly expanded, connecting rings thin. Radial canals within the siphuncle from broad arcs that may bifurcate close to the parispatium. Derivation and phylogeny ''Lambeoceras'' is derived from the same stock in '' Actinoceras'' that produced ''Kochoceras'' according to Flower ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wutinoceratidae
The Wutinoceratidae are a family of early actinocerids defined by Shimazu and Obata in 1938Flower 1976. New American Wutinoceratidae with Review of Actinoceroid Occurrences in Eastern Hemisphere;PartI, Memoir 28; New Mexico Bureau of Mines and Mineral Resources 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 the internal deposits are penetrated by a system of canals.Teichert 1964. Actinoceratoidea, Treatise on Invertebrate Paleontology, part K.(Nautiloidea) The Wutinoceratidae include three genera,Flower 1957. Studies of the Actinoceratida. Memoir 2; New Mexico Bureau of Mines and Mineral Resources, Socorro, NM ''Wutinoceras'', ''Cyrtonybyoceras'', and ''Adamsoceras'', known especially from the early Middle Ordovician (Whiterock stage) in northeastern China and North America, but foun ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 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 The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic 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. T ...) 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 the upper Pogonip Group in Ikes Canyon in the Toquima Ran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lambeoceras
''Lambeoceras'' is a genus of large actinocerids with a convexly lenticular cross section from the Upper Ordovician of North America and the sole representative of the family Lambeoceratidae. Morphological description ''Lambeoceras'' is of medium to moderately large size with a long, straight, depressed shell, broad in cross section with the dorsum and venter both about equally convex, meeting acutely along the sides. Chambers are short, and septa are closely spaced, forming broad lobes on the upper and lower sides, which meet in sharp saddles along the sides. The siphuncle is submarginal, near the ventral side and relatively narrow. Septal necks are extremely long, brims short and recumbent. Segments are broadly expanded, connecting rings thin. Radial canals within the siphuncle from broad arcs that may bifurcate close to the parispatium. Derivation and phylogeny ''Lambeoceras'' is derived from the same stock in '' Actinoceras'' that produced ''Kochoceras'' according to Flower ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Actinoceras
''Actinoceras'' is the principal and root genus of the Actinoceratidae, a major family in the Actinocerida, that lived during the Middle and Late Ordovician. It is an extinct genus of nautiloid cephalopod that thrived in the warm waters of the United States during the Paleozoic era. Morphology ''Actinoceras'' are generally large, with typically straight shells reaching a meter or so in length (about 3 ft), with a blunt apex, and usually with a circular to subcircular cross section. . Shell characteristics The shells of ''Actinoceras'' are generally straight and long, although some are breviconic. Some are fusiform with the diameter decreasing from the anterior end of the phragmocone toward the aperture. Chambers are short and contain cameral deposits which are more concentrated apically and ventrally. Septa are close spaced, sutures are mostly transverse. The siphuncle, which varies in proportion to the size of the shell among species, is ventral, but not on the ventral ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Actinoceratidae
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.Teichert 1964. Actinoceratoidea, Treatise on Invertebrate Paleontology, part K.(Nautiloidea) 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 Actinoceratids are derived from ''Wutinoceras'', possibly through an early '' Armenoceras'' or through '' Nybyoceras''Flower 1957.Studies of the Actinoceratida; Memoir 2; New Mexico Bureau of Mines and Mineral Resources, Socorro, NM and give rise to ''Lambeoceras'' and to the Huroniidae. Seven genera are included in the Actinoceratidae, ''Actinoceras'', '' Flowerocer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Armenoceras
''Armenoceras'' is a genus of actinocerid nautiloid cephalopods whose fossils ranged from the late Whiterockian Stage in the early Middle Ordovician, through the remainder of the period and on into the Upper Silurian. It is the type genus of the family Armenoceratidae. The shells of ''Armenoceras'' are straight and medium to large in size with a circular to subcircular cross section. The siphuncle is large, located subcentrally to resting on the ventral margin. Segments are wider than long, broadly expanded into the camerae. Septal necks short with wide brings that may be in contact with posterior surface of septa. In most the canal system within the siphuncle in is of the double arc type. Cameral deposits are rare. ''Armenoceras'' is derived from ''Wutinoceras'' through a thinning of the connecting rings and a simplification of the endosiphuncular canal system. The earliest ''Armenoceras'' known comes from the lower Whiterock equivalent in northern China and Korea but is unkn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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