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.