Saturday, March 19, 2016

Coelospira virginia brachiopod from the Bois d'Arc formation of Oklahoma

When I'm out collecting I often pick up anything that looks like it might be a fossil and sometimes I know what it is while other times it just looks similar to another shell. Such is the case with Coelospira virginia. This is a very small shell that I probably thought was an Atrypina sp. when I tossed it into my collecting bag. It wasn't until I got home and really looked closely at it that I saw there was a difference. White it does have the same rounded shape as Atrypina sp. with a wide fold and sulcus, the radial ribs are narrower and the margin is flat rather than following the curve of the rib. This was the key feature that inspired me to look for another match. I found a good match while going through "Stratigraphy and Paleontology of the Hunton Group in the Arbuckle Mountain Region, Part V - Bois d'Arc Articulate Brachiopods " Amsden, 1958, Oklahoma Geological Survey Bulletin 82 on plate V, fig. 39.40.

Brachial valve
Pedicle valve

I found two specimens of  Coelospira virginia (one of which is shown on this page) in the Bois d'Arc formation (Cravatt Member) near Clarita, OK which is Devonian in age (Lockhovian stage). The Bois d'Arc overlies the Haragan formation but both are the same age (Devonian, Lockhovian stage). They are both roughly correlative to the Helderberg fauna of New York and thus are contemporaneous with the Coyemans, Kalkberg and New Scotland formations.

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