Orthospirifer sp. brachiopod from the Silica Shale

Years ago I purchased some brachiopods that came from the middle Devonian aged Silica Shale in Ohio. These were fossils that had been collected in the 80's and 90's and came from older collections. Among the various species were these two articulated shells. The label that came with them called them Orthospirifer sp. but they look very similar to Mediospirifer audaculus which is a somewhat common brachiopod species from the middle Devonian. I've done a little research and it seems to me that the most visual difference between Orthospirifer and Mediospirifer is that the brachial valve on Orthospirifer is a little more convex and the interarea is slightly recurved. On Mediospirifer the brachial valve is nearly flat and the interarea is straight. This is just based on my collecting experience and visual inspection of fossils in my collection.

Specimen #1 - brachial valve

Anterior

Pedicle valve

Posterior

Profile

Specimen #2 - brachial valve

Anterior

Pedicle valve

Posterior

Profile

Both specimens side by side.

Schizophoria ferronensis from the Silica Shale

Schizophoria is a genus of brachiopods that I have not personally collected much. I don't often find it in my preferred Middle Devonian outcrops and am aware of it mostly from the Upper Midwest portion of America.  This specimen comes from Milan, MI and is a Schizophoria ferronensis out of the Silica Shale (Devonian, Givetian stage). The large shells of Schizophoria can be identified by their oval outline, fine raidal ribs decorating the surface, wide but shallow sulcus and a shallow triangular dethyrium on the posterior of the pedicle valve.

Here are some other species: Schizophoria schnuri from Poland, Schizophoria iowaensis from Iowa.

Ambocoelia umbonata Brachiopod from the Silica Shale

Ambocoelia umbonata is an index fossil for me indicating the rocks layers can be dated to the Middle Devonian. It's distinctive size and shape make it hard to misidentify and it can be quite prolific in certain layers. The specimen below comes from the Silica Shale (Devonian, Givetian stage) and was collected at Sylvania, OH.

Brachial valve - With the foramen (circular opening through which the pedicle muscle extended) visible on the recurved pedicle valve

Anterior

Pedicle valve

Posterior

Profile

Here is a small specimen from the Widder Formation near Arkona.

I found this cool illustration from  "Revised Taxonomy and Autecology for the Brachiopod Genus Ambocoelia in the Middle and Late Devonian Northern Appalachian Basin (USA)" by James J. Zambito IV and Mena Schemm-Gregory, Journal of Paleontology 87(2):277-288. 2013. It shows what the possible life positions were for Ambocoelia umbonata (view 1) and Ambocoelia gregaria (view 2).

Cupularostrum prolificum brachiopod from the Silica Shale

Cupularostrum prolificum is a small ryhnchonellid type brachiopod from the Silica Shale (Devonian, Givetian stage). It is similar looking to brachiopods that are referred to as Camarotoechia and it seems as though there has been some name changes/swaps. I have not yet been able to find any papers which explain the reasoning or if both genus are valid or cospecific. The specimen below was collected in Pauldin, OH.

Brachial valve

Anterior

Pedicle valve

Posterior

Profile

I have found a similar looking specimen called Cupularostrum sappho in the Ludlowville Fm. along Lake Erie, NY.

Cyrtina hamiltonensis from the Silica Shale of Michigan

The triangular shape shell of Cyrtina is very easy to spot. It is a prolific member of many Devonian communities and is one of the more common fossils found. The specimen below is Cyrtina hamiltonensis and was found in the Silica Shale (Devonian, Givetian stage) at Milan, MI.

Brachial valve

Anterior

 Pedicle valve

Posterior

Profile

Some other examples of Cyrtina that I've blogged about are Cyrtina umbonata from Michigan, Cyrtina sp. from Iowa, Cyrtina arkonensis from Ontario, other Cyrtina species from Ontario.

Allow me a moment to explain my thought process behind this blog. The photo of the pedicle valve shown above was taken with far end of the pedicle valve in focus and so the tip closest to the camera is out of focus. Still, it gives you a view similar to those you find in older reference books with hand drawn illustrations of fossils. Imagine how frustrating it would be to try and ID your fossil when they only give you a view of the pedicle valve and brachial valve similar to my above pictures. This is part of the reason why I include anterior, posterior and profile views in my posts.

Cranaena romingeri brachiopod from the Silica Shale

The small Terebratulid brachiopod Cranaena romingeri is one of the few smooth shelled brachiopods that can be found in the Silica Shale (Devonian, Givetian stage).  It is distinctive despite it's rather mundane, unornamented appearance. The shell is oval shaped with two convex valves. The pedicle valve is a little longer than the brachial valve and is marked with an obvious circular depression (called the foramen) where the pedicle muscle would have extended outward. This specimen was collected from a quarry in Milan, MI.

Brachial valve

Anterior

Pedicle valve

Posterior

Profile

Mediospirifer audaculus brachiopod from the Silica Shale

A few months ago I posted about some Mediospirifer audaculus that I'd finally found fully articulated in the Moscow Formation of New York. Now I have a specimen of the same species from the Silica Shale of Milan, Michigan.The specimen below has a pedicle valve that is a little less deep than some of the specimens I have from New York but otherwise it looks very similar.

Brachial valve

Anterior (with some shelly debris obscuring the sulcus)

Pedicle valve

Posterior

Profile

The Silica Shale is Devonian in age and part of the Givetian stage.

Hercostrophia robusta brachiopod from the Silica Shale

Hercostrophia robusta is a new Strophomenid brachiopod for me. It was part of a lot of fossils from the Silica Shale of Paulding, Ohio but only had the partail, single valve. It has a superficial resemblance to Strophodonta demissa but the valve of H. robusta appears to be flatter and more like Protoleptostrophia perplana. The Silica Shale is Devonian in age (Givetian stage).

Pedicle valve exterior

Pedicle valve interior

Posterior hinge

Longispina lissohybus Brachiopod from the Silca Shale

I have found one specimen that I can ID as belonging to the Genus Longispina and that specimen was found in the Mahantango formation. Below is a specimen I purchased as part of a lot from E-bay that comes from the Silica Shale in Paulding, OH. The label indicates that it is Longispina lissohybus but the shell is missing the tell tale spines that normally extend from the hinge line on the left and right sides. The radial ribs that decorate the surface are a bit muted as well so I'm not sure if this really is L. lissohybus. Interestingly, there appears to be a predatory gastropod boring on the pedicle valve.

Pedicle valve

Anterior

Posterior

Profile

The Silica Shale is Devonian (Givetian stage) in age.

Devonochonetes scitulus brachiopod from the Silica Shale

I'm pleased to have an example of Devonochonetes scitulus from the Silica Shale near Sylvania, OH. This is a somewhat common brachiopod in the Givetian stage of the Devonian and I've found it in several units across the US.

Pedicle valve

Anterior

Brachial valve

Posterior

Profile

Here are some other examples of this species from the Arkona and Widder Formations at Arkona, Canada, the Mahantango Formation of Pennsylvania and a specimen from Germany that looks very similar.