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Showing results for tags 'rostricellula'.
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A nice Dictyonema flabelliforme dendroid graptolite from Oslo Fields in Norway. It's Tremadoc, Lower Ordovician in age and is thus maybe around 480 mya. Another angle :
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- amplexopora
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From the album: Brachiopods of Platteville/Decorah Twin Cities Minnesota
All sources had says there are only two genus of the family of this particular brachiopod and Protozgya and Rostricellula is listed for Platteville Formation. Protozyga is too different and much weaker ribs structures by comparations.-
- brachiopod
- minnesota
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From the album: Brachiopods of Platteville/Decorah Twin Cities Minnesota
Rostricellula minnesotensis. Seem to be Platteville formation only for me. Easily mistaken for Rhynchotrema wisconsinense until I noticed something odd with my specimens. The sulcus barely exists and sources usually says Rostricellula generally are smaller than Rhynchotrema. Plus the picture I had seen of Zygospira recurvirostris look significant different.-
- brachiopod
- minnesota
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Rhynchonellids are hard to identify by exterior morphology as they often need to have their internal structures visible to be sure of an id. However if you know the faunal lists from a specific area, you can reduce the candidates considerably. The specimen here has 22 costae with 4 on the fold and thus, at this size must be one of two species, Rostricellula minnesotensis or Rhynchotrema wisconsinensis. The only completely safe way to differentiate between the two is the presence or absence of a cardinal process in the brachial valve but this is not possible here. However, Rostricellula usually, though not always, devoid of shell ornamentation, such as ridges or the presence of growth lines, and Rhynchotrema wisconsinensis usually, though not always, shows these, though they can also be seemingly absent through wear. But, R. wisconsinensis never shows a length to width ratio of 1.00, only from 0.80 to 0.95 and this specimen has a ratio of 1.00 which does occur in Rostricellula. Furthermore, the fold of Rostricellula is wider and less sharply developed Finally, good specimens of Rostricellula are far more common than R wisconsinense at the locality as the species most commonly found here is Rhynchotrema ainsiei which is describe elsewhere and not to be confused with the other two due to it's larger number of costae Thus, I am fairly confident with my id
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- brachiopod
- caradoc
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