Thursday, February 18, 2016

Orthostrophia strophomenoides brachiopod from the Bois d'Arc formation of Oklahoma

Orthostrophia strophomenoides is a species that I have not found anywhere else from the lower Devonian but is fairly prolific in the Bois d'Arc formation of Oklahoma. I have posted about specimens from the Haragan formation in the past but other than that I have not seen any specimens of the genus from elsewhere in the world. The shell of Orthostrophia strophomenoides is subrectangular in outline with both valves being slightly convex. The surface of the valves are decorated with coarse striae and occasionally a concentric growth line. At the posterior the shell has a straight hinge line with a delthyrium that is about 3/4 the width of the shell.

Brachial valve
Pedicle valve

I found the specimen 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.

"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

1 comment:

  1. I find a lot of them in the Cravatt member also. They clean somewhat easily with dolomite powder and air abrasive. Also Quaternary O softens and loosens the matrix prior to air abrasive work. Most are partially silicified, and heavier than the ones from the Haragan formation.