Atrypa oklahomensis brachiopod from the Bois d'Arc formation of Oklahoma

The brachiopod genera Atrypa makes an appearance in the Bois d'Arc formation, as one would expect. It's pretty much an index fossil for the Devonian period as far as I'm concerned. In this case we have Atrypa oklahomensis. The shell is rounded with a very convex brachial valve and a slightly convex to flat pedicle valve. The surface of both valves have regularly spaced ribs and fine concentric growth lines. There is a small fold and sulcus present to some degree on every specimen I have found but this is only expressed at the anterior margin with no hint of continuation farther back in the shell. Perhaps this feature is only found in older, mature specimens? Otherwise the margin where the shells meet is relatively flat. The pedicle valve has a small umbo which extends past the brachial valve. There is little to no interarea visible along the hinge line.

Brachial valve

Anterior

Pedicle valve

Posterior

Profile

The specimens I found are somewhat larger compared to those I have from the Haragan formation.

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

Strophonella bransoni brachiopod from the Bois d'Arc formation of Oklahoma

Another flat brachiopod from the class Strophomenata that can be found in the Bois d'Arc formation is Strophonella bransoni. It has a rounded to subrectangular shape with a (notably) convex brachial valve and concave pedicle valve. The surface of the valves have many thin costellae decorating it, which stand out in relief somewhat, and on some specimens very fine concentric growth lines can be seen. Amsden's original description for the species indicates that the pedicle valve has a small beak that extends past the hinge line but none of the specimens I found have that portion visible enough for me to confirm. Strophonella bransoni can be distinguished from Stropheodonta gibbera by the smaller degree of convexity to the shell and the stronger, more rounded costellae.

Brachial valve

Anterior

Profile

Unfortunately this, and other, specimens that I found do not have either the hinge line (posterior) nor pedicle valve exposed enough to view and photograph adequately.

Specimen #2 - This specimen is more intriguing for the epibionts that decorate the shell.

This appears to be a holdfast of some sort, possibly from an Edriocrinus sp.?

I believe these next two pictures are of an inarticulate brachiopod valve that is cemented to the shell surface. Based on appearance, it could be a species of Petrocrania (which often have nondescript surfaces that often mimic the shells they have colonized as in this example).

A bryozoan also used the shell as a hard substrate.Perhaps a species of Lichenalia?

And finally a Spirobis sp. worm tube which looks like a tiny gastropod.

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

Eatonia sp. brachiopod from the Bois d'Arc formation of Oklahoma

I believe that this next Brachiopod is an Eatonia sp. While Eatonia medialis is listed by Amsden* as being known from the Haragan and Bois d'Arc formations of Oklahoma, the specimen below does not appear to conform to specimens I have found in the Kalkberg formation of New York or Licking Creek formation of Virginia (both formations are correlative to the aforementioned Oklahoma formations).

The shell is rounded to sub-pentagonal in shape with coarse plications. The pedicle valve has a sulcus which is relatively shallow except at the anterior margin which corresponds to a fold in the brachial valve. On the fold there are 4-5 plications. The pedicle valve has an umbo which extends past the brachial valve and curves slightly. The brachial valve is convex while the pedicle valve convex near the umbo but flattens by the time it reaches the margins. In fact, on my specimen, the pedicle valve is more inflated at the umbo than the specimens of E. medialis from New York or Virginia. This is what causes me to wonder if I have a different species or genera or if what I found is typical for the species in Oklahoma. Unfortunately I only have a single specimen so I do not have enough of a sample to draw a conclusion.

 Brachial valve

Anterior

Pedicle valve

Posterior

Profile

As I was looking through the "Paleontology of New York" Vol 3, pg 237, pl. 37, fig 3 & 4,  I found a specimen that seems to be close to the specimen shown above: Rhynchonella eminens. Below are screen grabs from the plate and the text of the original description.

It looks close to what I found except the outline of my fossil looks to be sub-pentagonal instead of ovoid or subglobose.

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, pg. 74

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