|
Alaoceras
''Alaoceras'' is an ammonoid cephalopod from the upper Paleozoic included in the goniatitid family Cravenoceratidae, named by Ruzhentsev & Bogoslovskaya in 1971. ''Alaoceras'' is characterized by its generally subdiscoidal shell with moderately involute whorls and a wide or moderately wide umbilicus, ornamented with sharply defined lamellae, very weak and sometimes disappearing lirae, and elongated protuberances on the umbilical wall. Normally there are one or two constrictions per revolution. The suture is goniatitic with a widely diverging bifurcated ventral lobe in which the height of the median saddle is less than half of the whole lobe. ''Alaoceras'' is probably derived from ''Pachylyroceras ''Pachylyroceras'' is a large, generally subglobular, Upper Mississippian gonitite and included in the cephalopod subclass Ammonoidea. Recognition ''Pachylyroceras'' produced a large shell that is moderately evolute to moderately involute and ...'', which it resembles overall. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pachylyroceras
''Pachylyroceras'' is a large, generally subglobular, Upper Mississippian gonitite and included in the cephalopod subclass Ammonoidea. Recognition ''Pachylyroceras'' produced a large shell that is moderately evolute to moderately involute and thickly discoidal to subglobular, with a rather wide umbilicus. Surface sculpture consists of coarse, widely spaced longitudinal lirae. Constrictions where present are wide and deep. Its suture has a narrow bifurcated ventral lobe with slightly divergent to subparallel sides and a median saddle less than half the height. Taxonomic position ''Pachylyroceras'', named by Ruzhentsev & Bogoslovskaia (1971), is included in the Neoglyphiocerataceae, (sometimes written Neoglyphioceratoidea), but its position within the superfamily varies according to whose classification. The revised version of the Treatise, Part L (W. M. Furnish et al. 2009 ) includes ''Pachylyroceras'' as well as '' Alaoceras'', '' Caenolyroceras'', '' Dombarigloria'', and ' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonoidea
Ammonoids are a group of extinct marine mollusc animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs, commonly referred to as ammonites, are more closely related to living coleoids (i.e., octopuses, squid and cuttlefish) than they are to shelled nautiloids such as the living ''Nautilus'' species. The earliest ammonites appeared during the Devonian, with the last species vanishing during the Cretaceous–Paleogene extinction event. Ammonites are excellent index fossils, and linking the rock layer in which a particular species or genus is found to specific geologic time periods is often possible. Their fossil shells usually take the form of planispirals, although some helically spiraled and nonspiraled forms (known as heteromorphs) have been found. The name "ammonite", from which the scientific term is derived, was inspired by the spiral shape of their fossilized shells, which somewhat resemble tightly coiled rams' horns. Pliny the Elder ( 79 AD nea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paleozoic
The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ''zōḗ'' (), "life", meaning "ancient life" ). It is the longest of the Phanerozoic eras, lasting from , and is subdivided into six geologic periods (from oldest to youngest): # Cambrian # Ordovician # Silurian # Devonian # Carboniferous # Permian The Paleozoic comes after the Neoproterozoic Era of the Proterozoic Eon and is followed by the Mesozoic Era. The Paleozoic was a time of dramatic geological, climatic, and evolutionary change. The Cambrian witnessed the most rapid and widespread diversification of life in Earth's history, known as the Cambrian explosion, in which most modern phyla first appeared. Arthropods, molluscs, fish, amphibians, reptiles, and synapsids all evolved during the Paleozoic. Life began in the ocean ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Goniatitida
Goniatids, informally goniatites, are Ammonoidea, 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 Permian–Triassic extinction event, 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 Ammonitida, ammonites, being free swimming and possessing a head with two well developed eyes and arms (or tentacles). G ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cravenoceratidae
The Cravenoceratidae is one of six families included in the ammonoid superfamily Neoglyphioceratoidea, which lived during the latter part of the Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ... era. Cravenoceratid genera have moderately evolute to involute, broad or thickly discoidal shells with a moderately narrow umbilicus. The surface is generally smooth, dominated by growth striae. Spiral ornamentation may be present, but reticulate ornament is absent. The ventral lobe is double pronged and relatively narrow, with the median saddle in most forms less than half of height of entire lobe itself. References The Paleobiology Database10/01/07 10/15/11 * Saunders, Work, and Nikolaeva, 1999. Evolution of Complexity in Paleozoic Ammonoid Sutures, Supplementary Material ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
