Leptanea rhomboidalis brachiopod from the Bois d'Arc formation of Oklahoma

As may be expected, one of the more common brachiopod fossils from the Bois d'Arc formation is Leptanea rhomboidalis. The shell of the specimens I found are typical for the species with a rectangular outline when viewed from the dorsal or ventral side. Both valves are relatively flat with wide, concentric growth rings and decorated with fine striae  The margins of both valves (except along the hinge) are turned 90 degrees from the rest of the shell and this is most noticeable at the anterior.

Specimen #1 - Pedicle valve

Anterior

Brachial valve

Posterior

Profile

Specimen #2 - Pedicle valve

Anterior

Brachial valve - mostly obscured by matrix

Posterior

Profile

The specimens above can be directly compared to specimens I have collected from the Kalkberg formation and Onondaga formation of New York which were deposited at about the same time. I have also written a post about a similar type shell from the Haragan formation that I have labelled as L. acuticuspidata.

I found the specimens 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.

References: 
"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