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Johns Valley Formation
The Johns Valley Formation is a geologic formation in Arkansas and Oklahoma. It preserves fossils dating back to the Carboniferous period. Paleofauna Bryozoans *'' Acanthocladia'' :''A. ouachitensis'' *''Fenestella'' :''F. bendensis'' :''F. grandis'' :''F. granularis'' :''F. kosomensis'' :''F. mimica'' :''F. oklahomensis'' *'' Leioclema'' :''L. pushmatahensis'' *'' Rhombopora'' :''R. johnsvalleyensis'' :''R. nitidula'' *'' Sulcoretepora'' :''S. elegans'' Cephalopods * '' Bactrites'' * ''Cravenoceras'' : ''C. scotti'' * '' Cyclocerid'' * '' Dentoceras'' : ''D. belemnitiforme'' * '' Eumorphoceras'' : ''E. plummeri'' * '' Gastrioceras'' : ''G. adaense'' : ''G. fittsi'' * '' Girtyoceras'' : ''G. limatum'' * '' Glaphyrites'' : ''G. oblatus'' : ''G. morrowensis'' * ''Goniatites'' : ''G. choctawensis'' : ''G. granosus'' * '' Homoceratoides'' : ''H. cracens'' * '' Mariceras'' * ''Metacoceras'' * '' Mitorthoceras'' : ''M. perfilosum'' * '' Mooreoceras'' : ''M. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Formation (stratigraphy)
A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers. A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by Abraham Gottlob W ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fenestella (bryozoan)
''Fenestella'' is a genus of bryozoans or moss animals, forming fan–shaped colonies with a netted appearance. It is known from the Middle Ordovician to the early Upper Triassic ( Carnian), reaching its largest diversity during the Carboniferous. Many hundreds of species have been described from marine sediments all over the world. Etymology ''Fenestella'' is Latin, meaning little window, from fenestra "window", for the window-like openings in the mesh of the skeleton of its colonies. Description The skeleton of ''Fenestella'' colonies consists of stiff branches that are interconnected by narrower crossbars (or dissepiments). Between two and eight individuals of the colony inhabit each of the opposing front sides of the approximately rectangular openings between the branches (or fenestule) in one row, and the void they left when they died can be recognized as two rows of small rimmed pores (or apertures) on the front of each branch. In well-preserved specimens these are c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Goniatites
''Goniatites'' is a genus of extinct cephalopods belonging to the family Goniatitidae, included in the superfamily Goniatitaceae. '' Hibernicoceras'' and '' Hypergoniatites'' are among related genera. Species Description The shell is generally globose with an open but narrow umbilicus, the surface commonly reticulate resulting from longitudinal lirae crossing transverse striae. The ventral lobe of the suture is rather narrow with a median saddle about or little less than half the height of entire lobe. The first lateral saddle is subangular to angular. Distribution Fossils of species within this genus have been found widespread in North America, Eurasia, and north Africa. In particular they have been found in the Triassic of Italy, United States, in the Permian of United States, in the Carboniferous of the Czech Republic, Germany, Ireland, Morocco, United Kingdom, United States, in the Mississippian of United States, as well in the Devonian of the Czech Republic, Spain, Unit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gastrioceras
''Gastrioceras'' is a goniatitid genus in the family Gastrioceratidae that lived during the late Carboniferous (Pennsylvanian and for most of the Permian The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.9 Mya. It is the last period of the Paleoz .... Taxonomy ''Gastrioceras'' is assigned to the Gastrioceratidae, a family that makes up part of the Gastriocerataceae, known in more recent references as Gastrioceratoidea. , Morphology The ''Gastrioceras'' shell, or conch, is subdiscoidal to subglobose in form with moderate to wide umbilicus. Ornament varies according to species, varying from simple transverse lirae to reticulate produced by the addition of faint longitudinal lirae. The umbilical shoulder is nodose, nodes elongated transversely. Some species have rather strong ribs. The suture is characterized by a ventral lo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cravenoceras
''Cravevoceras'' is an Upper Paleozoic ammonite in the goniatite family Cravenoceratidae, probably derived from ''Pachylyroceras'' and contemporary with other cravenoceratid genera like '' Caenolyroceras'', '' Tympanoceras'' and later ''Alaoceras'' and '' Lyrogoniatites''. It is also a member of the Neoglyphioceratoidea. Description The shell of ''Cravenoceras'' is thickly discoidal to globose and moderately to widely umbilicate. Young stages are mostly extremely evolute. Sculpture consists of transverse lamellae, which are more or less straight on the flanks, but form a shallow ventral sinus. Longitudinal lirae mostly absent or very faint, sometimes restricted to umbilical shoulder. Constrictions are weak or absent. The ventral lobe is narrow, with a relatively low median saddle. Taxonomic position The revised Treatise (Furnish et al. 2009) includes ''Cravenoceras'' in the family Cravenoceratidae and subfamily Cravenoceratinae, along with 8 other genera including '' Tympan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cephalopod
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 i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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