Atrypa is a genus of brachiopod with round to short egg-shaped shells covered with many fine radial ridges (or costae). Growth lines form perpendicular to the costae and are spaced approximately 2 to 3 times further apart than the costae.. The pedunculate valve is slightly convex, but oftentimes levels out or becomes slightly concave toward the anterior margin (opposite the hinge and pedicle). The brachial valve is highly convex. Neither valve contains an interarea (a flat area bordering the hinge line, approximately perpendicular with the rest of the valve). Atrypa had a large geographic range and occurred from the late Lower Silurian (Telychian) to the early Upper Devonian (Frasnian).[4] Other sources expand the range from the Late Ordovician to Carboniferous, approximately from 449 to 336 Ma.[3] A proposed new species, A. harrisi, was found in the trilobite-rich Floresta Formation in Boyacá, Colombia.[5]
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| Atrypa reticularis, 26mm, Eifel, Germany | |
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| Genus: | Atrypa Dalman, 1828
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Cleiothyris Phillips, 1841, Mikrothyris | |
Reassigned species edit
As Atrypa was established in the 18th century, many species have since been reassigned.[4]
Organic content of Atrypa fossils edit
Organic compounds may be preserved in some Atrypa fossils. However, only the more stable amino acids tend to be preserved in older Atrypa fossils. In specimens of Atrypa reticularis from the Wenlock Shales (Lower Silurian), alanine, glycine, glutamic acid, leucine, isoleucine, proline, valine, and aspartic acid have been found.[4]
Gallery edit
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Atrypa devoniana, pedicle valve -
Atrypa devoniana, brachial valve -
Atrypa devoniana, anterior view -
Atrypa devoniana, posterior view -
Atrypa devoniana, lateral view -
Atrypa sp.; Couvinian (Middle Devonian); El Pical, Leon, Spain. Eroded to show spiralia on the right.
See also edit
References edit
- ^ Paleobiodiversity in Baltoscandia. "Atrypa (Atrypa) reticularis". fossiilid.info. Retrieved 2012-03-22.
- ^ M.A. Stainbrook (1945). Brachiopoda of the Independence Shale of Iowa. Geological Society of America Memoirs. Vol. 14. ISBN 0813710146.
- ^ a b c d e f Atrypa at Fossilworks.org
- ^ a b c Moore, R.C. (1965). Brachiopoda. Treatise on Invertebrate Paleontology. Vol. Part H., Volume 1 and 2. Boulder, Colorado/Lawrence, Kansas: Geological Society of America/University of Kansas Press. ISBN 0-8137-3015-5.
- ^ Floresta Series Fauna at Fossilworks.org
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