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Silica Shale: Fossil Identification Page

Ordovician Reef Fossils

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Click on the type of fossil or scroll down to browse:

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Trilobites

Trilobites are a group of extinct arthropods (similar to crustaceans) with a hard shell. They are common in Devonian rocks of Ohio. Unfortunately, almost all are fragments. Occasionally whole ones are found. The whole trilobites are usually found enrolled.

The most common type of trilobite found is Eldredgops milleri (Formerly known as Phacops rana).

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Eldredgops milleri (Formerly known as Phacops rana)

Like all fossils found in the Silica Formation, trilobites are exquisitely preserved. Eldredgops trilobites grew to large sizes in the Silica shale. Some of the best Eldredgops trilobites in the United States come from the Silica Shale.

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Brachiopod Fossils

Brachiopods are similar to mollusks, like clams, however, they are not closely related. Unlike most present day mollusks, the two shells of a brachiopod were different sizes.

Brachiopods were the dominant form of life in the seas in most of the Paleozoic, including the Devonian. Therefore, they are a very common fossil of the Devonian coral reefs in Western New York. Dozens upon dozens of species and genera can be found in the fossilized Devonian coral reefs.

Many genera and species Brachippods occur in the Silica Shale, the Devonian of Ohio. Below are a few example fossils.

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Mucrospirifer mucronatus (Conrad)

M. Mucronatus is a small to medium sized brachiopod fossil. It is very beautiful in that the hinge line is straight and very long, ending in a spine-like point. The term Mucronate means to end abruptly in a point.
Unfortunately, the mucronate ends are often broken off.

They are very wide, usually 3 or 4 times wider than the height. They have radial striations, and often numerous growth lines are visible.

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Mediopirifer Audaculus (Spirifer Audaculus)

These fossil brachiopods are more robust looking than M. mucronatus. Also the hinge line is not as straight as in M. mucronatus, and they are less elliptical, in that their width and height are not in as extreme proportions as M. mucronatus. They have more of a semi-circle shape.

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Stropheodonta Demissa (Conrad)

This is a medium sized brachiopod fossil. It has an easily identifiable shape, looking like a half-circle. The pedical valve is very convex, while the brachial valve is concave. It also has strong radial striations running the length of both shells.

There is a very similar looking brachiopod called Megastrophia concava. However, it is much larger in size.

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Megastrophia concava

These giant brachiopods are one of the larger types of Brachiopod fossils found in the Silica shale. They look like Stropheodonta brachiopods, but are MUCH larger.

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Coral Fossils

The Silica Formation contains a rich variety of corals. The corals easily weather from the shale and are therefore easy to collected. The genera in the images below include: Bethanyphyllum (Stumm), Heliophyllum (Hall), Heterophrentis (Hall), and possilbly others.

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Horn Corals

Horn corals are solitary corals that are cone shaped. They are abundanct in the Silica Shale.

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Recommended Book for Fossils of Ohio:

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Recommended Ohio Book:

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Fossils of Ohio (Bulletin 70)
By Rodney M. Feldmann (ed)
Copyright 1996
State of Ohio Div. of Geological Survey

This book is a MUST for anyone collecting in Ohio or nearby Devonian formations. It has detailed descriptions and images of 100's of fossils one can find throughout Ohio, including the Cincinnati Arch. It can be ordered through the Ohio DNR website, just search for "Fossils of Ohio (Bulletin 70)"

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Recommended Trilobite and Fossil Hunting Books: