Rhipdomelloides oblata brachiopod from the Bois d'Arc formation of Oklahoma

Perhaps the most common fossil brachiopod to be found in the Bois d'Arc formation is Rhipidomelloides oblata. Most are small but some can get about an inch in width. The shell is rounded to subrectangular with both valves generally convex. A gentle curve is sometimes present in the anterior margin. The pedicle valve has a beak that recurves over the brachial valve. Both valves have fine striae and concentric lines decorating their surface.

Pedicle valve

Anterior

Brachial valve

Posterior

Profile

While this next fossil is somewhat large it is also compressed nearly flat which makes it more difficult to identify. I'm a fairly confident though that this too is a specimen of Rhipidomelloides oblata. The shell is rounded to ovate with both valves decorated with numerous fine costae. This specimen is flattened but in life both valves would have been slightly convex. The posterior is mostly obscured by matrix or by the shell being flattened.

Brachial valve

Anterior

Pedicle valve

Posterior

Profile

I wrote a post about similar specimens of Rhipdomelloides oblata from the Haragan formation.

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

Stropheodonta gibbera brachiopod from the Boid d'Arc formation of Oklahoma

The highly convex shape of the shell of this next specimen is indicative of the species Stropheodonta gibbera. I collected it from the Bois d'Arc formation in Oklahoma. The shell is subrectangular in shape with a rounded anterior margin and straight hing line. The pedicle valve is very convex while the brachial valve is very concave. This arrangement of valves is typical of the class Strophomenata. The surface of both valves have fine costellae that have low relief and fine concentric growth lines. The strong convexity of the shell, which led to the specific name to be inspired by from the Latin word "gibbus", and the appearance of the costellae help distinguish this species from other, similar shells.

Pedicle valve

Anterior

Brachial valve - filled with matrix

Posterior

Profile

Here is a specimen from the Haragan formation that I blogged about before.

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 and Haragan formations interfinger with each other and are roughly 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

Inarticulate brachiopods from the Bois d'Arc formartion

The Bois d'Arc formation has some inarticulate brachiopods that can be found but they are often fragile and weather away quickly. I was fortunate enough to find two examples of varying preservation. I can't locate any literature that describes species that could be found and it appears that the inarticulate brachiopods were ignored by Amsden when he initially described the brachiopod fauna from the Lower Devonian of Oklahoma.

The first is a Lingula type specimen. I am not sure if the shell is warped or fractured as it appears the remaining shell material forms a halo of sorts around some matrix which has additional shell on it.

The other specimen appears to be similar to an Orbiculoidea type inarticulate brachiopod but there is precious little preserved to help identify it.

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

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

Anterior

Pedicle valve

Posterior

Profile

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.

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

Meristella atoka brachiopod from the Bois d'Arc formation of Oklahoma

I've written about the brachiopod Meristella atoka from the Haragan formation of Oklahoma a few years back, but these next examples come from the Bois d'Arc formation. Both have the typical subtriangular to subpentagonal shape (this means they are roughly shaped like a triangle or pentagon when looking at a valve from the dorsal or ventral side), smooth shell with just a few concentric growth lines and a simple fold and sulcus. The latter feature is highly variable as can be seen in the two specimens below and when one compares the specimen from the Haragan formation linked above.

Brachial valve

Anterior

Pedicle valve

Posterior

Profile

Specimen #2 -  Pedicle valve (with a bit of Limonite/Pyrite coating)

Anterior

Brachial valve

Posterior - The Limonite/Pyrite coating covers the beak.

Profile

Another view of the Limonite/Pyrite coating. I don't believe this is a replacement of the shell, rather it could have been something that developed after the shell was buried in a low oxygen environment.

I think this next specimen may be a juvenile specimen of the same species. Pedicle valve

 Anterior

 Brachial valve

 Posterior

 Profile

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

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

Anastrophia grossa brachiopod from the Bois d'Arc formation of Oklahoma

The genus Anastrophia first becomes widely seen in the Silurian and it extends into the lower Devonian before disappearing from the fossil record. The specimens below are Anastrophia grossa from the Bois d'Arc formation of Oklahoma. The shell is subpentagonal in outline with coarse costae present on both valves. There is a shallow sulcus on the pedicle valve that becomes much more expressed at the anterior margin forming a "u" shape. The corresponding fold is also shallow. Both valves are convex with the brachial valve being more so than the pedicle valve.


Pedicle valve

Anterior

Brachial valve

Posterior

Profile

Specimen #2 - Brachial valve

Anterior

Pedicle valve

Posterior

Profile

I have not found any specimens of Anastrophia from the rocks of the Helderberg group in New York yet, but according to Amsden and Boucot, in their Bulletin 78 from the Oklahoma Geological Survey "Stratigraphy and Paleontology of the Hunton Group in the Arbuckle Mountain Region", 1958, there is a species, A. verenuili, known from there and they compare the Oklahoma species to it:

"A. grossa differs from A. verenuili in several respects, one of the most important differences being in the nature of the brachial umbo. This part of the brachial valve on the New York species is swollen and extends posteriorly well beyond the pedicle beak, whereas in A. grossa the umbo is not so enlarged and extends only slightly, if at all, behind the pedicle beak."

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.

Compare these specimens to some from the Silurian rocks of the Waldron Formation of Tennessee, and the Wenlock formation of England.

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