Atrypa Explained

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).^[1] Other sources expand the range from the Late Ordovician to Carboniferous, approximately from 449 to 336 Ma.^[2] A proposed new species, A. harrisi, was found in the trilobite-rich Floresta Formation in Boyacá, Colombia.^[3]

Reassigned species

As Atrypa was established in the 18th century, many species have since been reassigned.^[1]

A. arata = Pentamerella arata
A. aspera var. occidentalis = Spinatrypa occidentalis
A. astuta = Felinotoechia astuta
A. congregata = Camarotoechia congregata
A. coralifera = Eodictyonella coralifera
A. depressa = Plagiorhyncha glassii
A. dubia = Protorhyncha dubia
A. elongata = Rensselaeria elongata
A. exigua = Protozyga exigua
A. extans = Triplesia extans
A. flabellites = Leptocoelia propria
A. gruenwaldtiaeformis = Nalivkinia gruenwaldtiaeformis
A. hemiplicata = Parastrophina hemiplicata
A. hemisphaerica = Eocoelia hemisphaerica
A. hircina = Hircinisca hircina
A. hirsuta = Parazyga hirsuta
A. hystrix var. occidentalis = Spinatrypa occidentalis
A. increbescens = Rhynchotrema increbescens
A. kolymensis = Vagrania kolymensis

A. laevis = Meristella laevis
A. lens = Stricklandia lens
A. linguifera = Antirhynchonella linguifera
A. medialis = Eatonia medialis
A. modesta = Zygospira modesta
A. nitens = Hisingerella nitens
A. nitida = Whitfieldella nitida
A. nucella = Lycophoria nucella
A. obovata = Glassia obovata
A. obtusiplicata = Pectorhyncha obtusiplicata
A. peculiaris = Costellirostra peculiaris
A. plebeia = Dicamara plebeia
A. pleiopleura = Pleiopleurina pleiopleura
A. prunum = Atrypella prunum
A. recurvirostra = Zygospira recurvirostra
A. scitula = Charionella scitula
A. sordida = Cyclocoelia sordida
A. tumida = Meristina tumida
A. unisulcata = Pentagonia peersii

Organic content of Atrypa fossils

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.^[1]

Notes and References

Book: Moore, R.C.. 1965. Brachiopoda. Geological Society of America/University of Kansas Press. Treatise on Invertebrate Paleontology. Part H., Volume 1 and 2. Boulder, Colorado/Lawrence, Kansas. 0-8137-3015-5.
http://www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=21443 Atrypa
http://www.fossilworks.org/cgi-bin/bridge.pl?a=collectionSearch&collection_no=36012 Floresta Series Fauna