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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]
| Atrypa | |
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| Atrypa reticularis, 26mm, Eifel, Germany | |
| Scientific classification | |
| Kingdom: | |
| Phylum: | |
| Class: | |
| Order: | |
| Suborder: | †Atripidina |
| Family: | †Atrypidae |
| Genus: | Atrypa Dalman, 1828 |
| Species | |
| Synonyms | |
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Cleiothyris Phillips, 1841, Mikrothyris | |
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As Atrypa was established in the 18th century, many species have since been reassigned.[4]
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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]
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.
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