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Alocolytoceratinae
Alocolytoceratinae is a subfamily of lytoceratids that comprises genera characterized by many deep constrictions in the shell resulting in capricorn-like (goat's horm) ornamention, especially in the middle whorls, but becoming smooth and more involute in the outer whorls. Saddle endings in the suture tend to be phylloid, (leaf-like). Alcolytocerainae includes ''Alocolytoceras'', ''Lobolytoceras ''Lobolytoceras'' is an extinct genus of ammonite in which only the inner whorls have large swollen ribs, later whorls have wrinkled growth lines which coarsen somewhat, near the aperture. The genus is known from the Lower Jurassic Toarcian of Eu ...'', '' Pachylytocras'', and '' Pleurolytoceras'', which are mostly from the Toarcian. One genus, ''Pachylotoceras'', extends into the lower Bajocian. References ;Notes ;Bibliography *W.J.Arkell, B.Kummel, & C.W.Wright 1957. Mesozoic Ammonoidea, Treatise on Invertebrate Paleontology, Part L Ammonoidea. R.C.Moore, (ed). Early Jurassic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alocolytoceras
''Alocolytoceras'' is a lytoceratid ammonite 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) ... with whorls that pass during growth from round to oval, rounded-quadrate, or compressed; with about 19 deep constrictions per whorl, with as many as 21 sharp ribs in between. The shell is evolute. All whorls are visible from either side. ''Alocolytoceras'' belongs to the lytoceratid subfamily Alocolytoceratinae, which also includes '' Pachylytoceras'' and '' Pleurolytoceras''. It is known from the upper Lower Jurassic of Europe and the Himalaya. References ;Notes ;Bibliography * Jurassic ammonites Early Jurassic ammonites of Europe Ammonitida genera Lytoceratidae {{ammonitida-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Audaxlytoceras
''Audaxlytoceras'' is an extinct genus of lytoceratid ammonites. Taxonomy The Middle Jurassic '' Nannolytoceras'' is its closest relative. '' Aegolytoceras'' and '' Peripleuroceras'' Tutcher and Trueman 1925 are synonyms. Fossil record This genus is known in the fossil record from the Lower Jurassic (Pliensbachian) (from about 190.8 to 182.7 million years ago). Fossils of species within this genus have been found in France, Germany, Italy, Morocco and Spain. Description Its shell is small, smooth, evolute (all whorls showing), only slightly impressed dorsally (along the inner rim). Whorls are compressed, subquadrate in section, higher than wide, with few narrow constrictions. The suture relatively simple with a long ventral lobe and two lateral lobes.Arkell ''et al.'', 1957. Mesozoic Ammonoidea, Systematic Descriptions. Treatise on Invertebrate Paleontology Part L, Ammonoidea. Geol Soc of Amer. and Univ Kans. Press. L199 Bibliography *Arkell ''et al.'', 1957. Mesozoic Ammo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lobolytoceras
''Lobolytoceras'' is an extinct genus of ammonite in which only the inner whorls have large swollen ribs, later whorls have wrinkled growth lines which coarsen somewhat, near the aperture. The genus is known from the Lower Jurassic Toarcian of Europe. The type species ''L. siemensi'' (Denck) came from the Upper Toarcian of Germany. References Jurassic ammonites Fossils of Germany Toarcian life Ammonitida genera Lytoceratidae {{ammonitida-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Toarcian
The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma (million years ago) and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian. The Toarcian Age began with the Toarcian turnover, the extinction event that sets its fossil faunas apart from the previous Pliensbachian age. It is believed to have ended with a global cooling event known as the Comptum Cooling Event, although whether it represented a worldwide event is controversial. Stratigraphic definitions The Toarcian takes its name from the city of Thouars, just south of Saumur in the Loire Valley of France. The stage was introduced by French palaeontologist Alcide d'Orbigny in 1842, after examining rock strata of this age in a quarry near Thouars. In Europe this period is represented by the upper part of the Lias. The base of the Toarcian is defined as the place in the stratigraphic record where the ammonite genus '' Eoda ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bajocian
In the geologic timescale, the Bajocian is an age and stage in the Middle Jurassic. It lasted from approximately 170.3 Ma to around 168.3 Ma (million years ago). The Bajocian Age succeeds the Aalenian Age and precedes the Bathonian Age. Stratigraphic definitions The Bajocian Stage takes its name from the Latin name (Bajocae) of the town of Bayeux, in the region of Normandy in France. The stage was named and introduced in scientific literature by French palaeontologist Alcide d'Orbigny in 1842. The base of the Bajocian stage is defined as the place in the stratigraphic column where fossils of the ammonite genus ''Hyperlioceras'' first appear. A global reference profile (a GSSP) for the base is located at Murtinheira, close to Cabo Mondego in Portugal.The GSSP is described by Pavia & Enay (1997) The top of the Bajocian (the base of the Bathonian) is at the first appearance of ammonite species ''Parkinsonia convergens''. Subdivision The Bajocian is often divided into Lower/Early ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Early Jurassic Ammonites
{{disambiguation, geo ...
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Toarcian First Appearances
The Toarcian is, in the ICS' geologic timescale, an age and stage in the Early or Lower Jurassic. It spans the time between 182.7 Ma (million years ago) and 174.1 Ma. It follows the Pliensbachian and is followed by the Aalenian. The Toarcian Age began with the Toarcian turnover, the extinction event that sets its fossil faunas apart from the previous Pliensbachian age. It is believed to have ended with a global cooling event known as the Comptum Cooling Event, although whether it represented a worldwide event is controversial. Stratigraphic definitions The Toarcian takes its name from the city of Thouars, just south of Saumur in the Loire Valley of France. The stage was introduced by French palaeontologist Alcide d'Orbigny in 1842, after examining rock strata of this age in a quarry near Thouars. In Europe this period is represented by the upper part of the Lias. The base of the Toarcian is defined as the place in the stratigraphic record where the ammonite genus '' Eodacty ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Middle Jurassic Extinctions
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