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Masonoceras
''Masonoceras'' is a genus of Karagondoceratids from Lower Mississippian strata, the shell of which is thinly subdiscoidal to discoidal with an acute ventral margin in late ontogeny. Whorls are strongly embracing, umbilicus narrow to occluded. The mature external suture contains a wide trifid ventral lobe, the flanking prongs longer that the medial, an asymmetrically rounded lateral saddle and a deeper asymmetric pointed lateral lobe. Internal molds of the type, ''Mesoceras Kentuckiense'' show presence of a broad hyponomic sinus flanked by high rounded vantrolateral salients. ''Mesonoceras'' is similar in general form to tis probable ancestor ''Karagandoceras ''Karagandoceras'' is an ammonoid genus belonging to the goniatid family Karagandoceratidae that lived during the early Mississippian (lower Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 ...'' but differs primarily in its pointed asymmetric lateral lobe, that of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Karagandoceras
''Karagandoceras'' is an ammonoid genus belonging to the goniatid family Karagandoceratidae that lived during the early Mississippian (lower Carboniferous The Carboniferous ( ) is a geologic period and system of the Paleozoic that spans 60 million years from the end of the Devonian Period million years ago ( Mya), to the beginning of the Permian Period, million years ago. The name ''Carbonifero ...). ''Karagandoceras'' has an involute, lenticular shell, with an acute ventral margin. The ventral lobe of the suture is wide with subparallel to divergent sides, divided by a median saddle with a relatively wide median lobe. Karagandoceratids, which include ''Karagandoceras'' and '' Mesonoceras'' are a rare offshoot of the Prionorceratinae that differ from their parent group by possession of an acute ventral margin and an increasingly trifid ventral lobe. References Paleobiology database-''Karagandoceras''8/22/10 8/22/10 * ''Masonoceras'', a new Karaganoceratid Ammonoid fro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mississippian (geology)
The Mississippian ( , also known as Lower Carboniferous or Early Carboniferous) is a subperiod in the geologic timescale or a subsystem of the geologic record. It is the earlier of two subperiods of the Carboniferous period lasting from roughly 358.9 to 323.2 million years ago. As with most other geochronologic units, the rock beds that define the Mississippian are well identified, but the exact start and end dates are uncertain by a few million years. The Mississippian is so named because rocks with this age are exposed in the Mississippi Valley. The Mississippian was a period of marine transgression in the Northern Hemisphere: the sea level was so high that only the Fennoscandian Shield and the Laurentian Shield were dry land. The cratons were surrounded by extensive delta systems and lagoons, and carbonate sedimentation on the surrounding continental platforms, covered by shallow seas. In North America, where the interval consists primarily of marine limestones, i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Goniatitida Genera
Goniatids, informally goniatites, are ammonoid cephalopods that form the order Goniatitida, derived from the more primitive Agoniatitida during the Middle Devonian some 390 million years ago (around Eifelian stage). Goniatites (goniatitids) survived the Late Devonian extinction to flourish during the Carboniferous and Permian only to become extinct at the end of the Permian some 139 million years later. Morphology All goniatites possessed an external shell, which is divided internally into chambers filled with gas giving it buoyancy during the life of the animal. An open chamber at the front of the shell provided living space for the goniatitid animal, with access to open water through a ventral siphuncle. The general morphology and habit of goniatites was probably similar to that of their later relatives the ammonites, being free swimming and possessing a head with two well developed eyes and arms (or tentacles). Goniatite shells are small to medium in size, almost always ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |