Atrypa

Atrypa is a genus of brachiopod with shells round to short egg-shaped, covered with many fine radial ridges (or costae), that split further out and growthlines perpendicular to the costae and 2-3 times wider spaced. The pedunculate valve is a little convex, but tends to level out or even become slightly concave toward the anterior margin (that is: opposite hinge and pedicle). The brachial valve is highly convex. There is no interarea (that is a flat area bordering the hinge line approximately perpendicular with the rest of the valve) in either valve. "Atrypa" was a cosmopolitan and occurred from the late Lower Silurian (Telychian) to the early Upper Devonian (Frasnian). Other sources expand the range from the Late Ordovician to Carboniferous, approximately from 449 to 336 Ma. A proposed new species, "A. harrisi", was found in the trilobite-rich Floresta Formation in Boyacá, Colombia.
Reassigned species.
As "Atrypa" was erected early on, many species have been reassigned since.
Organic content of "Atrypa" fossils.
In some fossil material, organic compounds may be preserved. Only the more stable amino acids tend to be preserved in very old 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.