Atrypa oklahomensis

Atrypa (Dalman 1827) is a very common brachiopod throughout the Silurian and Devonian periods and is one of my favorite fossils. It is no suprise to me then to find it among fossils gathered from White Mound in Oklahoma. The specimen shown below is possibly A. oklahomensis based on the book "Stratigraphy and Paleontology of the Hunton Group in the Arbuckle Mountain Region" 1958 Thomas Amsden and Arthur Boucot, Oklahoma Geological Survey, Bulletin 78 pgs:116-121. The entry on this species indicates that while most specimens of Atrypa tend to be put in the A. reticularis this is not always the case. I need to do more research to be able to tell the difference, but I will defer to Amsden and Boucot at this time.


Pedicle Valve



Front


Brachial Valve


Rear


Profile


This specimen came from an old estate collection of fossils that were collected in the 1960's to 1970's from the Haragan Formation at White Mound, OK. The Haragan formation is thought to range from the upper Silurain, 418mya, to the lower Devonian, 411mya ( Pridoli to Lochkovian). This would correspond to the Birdsong shale of Tennessee and the Helderberg Fauna of New York, Pennsylvania and Maryland.