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Showing results for tags 'lower toarcian'.
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From the album: Ammonites of the Betic Ranges (Spain) and world
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- ammonites
- lower toarcian
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From the album: Ammonites of the Betic Ranges (Spain) and world
Lytoceras sp. in glauconite. Lower Pliensbachian. Betic Range (Spain)-
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- ammonites
- lower toarcian
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Reference here
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- levisoni zone
- lower toarcian
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Index fossil for zone and subzone. Also known as Harpoceras falciferum. Literature: Howarth, M.K. (1973): The Stratigraphy and Ammonite Fauna of the Upper Liassic Grey Shales of the Yorkshire Coast. Bulletin of the British Museum (Natural History) Geology. Vol.24 No.4 Howarth, M.K. (1992): The Ammonite Family Hildoceratidae in the Lower Jurassic of Britain. Monograph of the Palaeontographical Society.
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- a903
- falcifer zone
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This species gives its name to the zone and subzone at the bottom of the lower Toarcian. This very fine-ribbed specimen of the genus Dactylioceras is for me a fine representative for the legend of St. Hilda, the Abbess at the monastery in Whitby ca. 650 A.D. She wanted to build a convent there as well, but the grounds were infested with snakes, so she prayed so intensively that all of the snakes were turned into stone. Since then they are known as snakestones. I found this sample pretty well as is with a head that reminds us of a snake. Literature: Howarth, M.K. (1973): The Stratigraphy and Ammonite Fauna of the Upper Liassic Grey Shales of the Yorkshire Coast. Bulletin of the British Museum (Natural History) Geology. Vol.24 No.4
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- a421
- dactylioceras tenuicostatum
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The last three photos show a specimen from the Whitby Mudstone Formation in Yorkshire in pyrite conservation. The diagnosis for distinguishing this species from D.commune, which is quite similar, can be found in the collection here under that species. Literature: Howarth, M.K. (1973): The Stratigraphy and Ammonite Fauna of the Upper Liassic Grey Shales of the Yorkshire Coast. Bulletin of the British Museum (Natural History) Geology. Vol.24 No.4
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This species was one of the most common of its time, but nevertheless it is used as the index fossil for the subzone since its occurence is practically limited to it. It is not easy to differentiate it from the species D.athleticum, which occurs in the same subzone. One main difference is that D.commune has a more rounded whorl section than D.athleticum, which is more oval. Another is that the number of ribs per whorl by D.athleticum remains constant, whereas D.commune has less ribs on the outer whorls as on the inner ones. The first specimen is from France (4 photos), the next 2 photos show a pyritized version in a concretion from a site near Whitby, Yorks., UK as well as the cut and polished version in the last photo. Both come from the Whitby Mudstone Formation. It's always interesting to observe how the same species can be preserved so differently depending in the particular conditions under which they were fossilized. Literature: Howarth, M.K. (1973): The Stratigraphy and Ammonite Fauna of the Upper Liassic Grey Shales of the Yorkshire Coast. Bulletin of the British Museum (Natural History) Geology. Vol.24 No.4