Two Pyrite Replaced Brachiopod (Paraspirifer) Fossils - Ohio

These are two brachiopod fossils of the species Paraspirifer bownockeri that have been replaced by glittering pyrite. They come from the Devonian aged Silica Shale near Sylvania, Ohio. The brachiopods have been prepped free from the surrounding rock, though a large slab of the rock has been left attached for presentation purposes. The center brachiopod appears as though it was removed from the rock during preparation, later to be remounted in the same spot. The quarries where these brachiopods used to be found are now closed to collectors so they are much harder to acquire.

Brachiopods are members of the phylum Brachiopoda. They are clam-like with wide shells composed of two halves called valves. They are filter feeders that live fixed to rocks or on the seafloor. Brachiopods first appeared in the early Cambrian as simple forms with non-articulating shells. Their diversity peaked during the Devonian, and there are currently 12,000 described fossil species of Brachiopoda from 5,000 genera. Most species of brachiopod died out during the Permian-Triassic Extinction but about 450 species still live today. They live in cold marine environments like polar seas or continental shelves and slopes. The largest fossil Brachiopod found is 7.9 inches (200 mm), but most are 2-4 inches (3-8 cm). Living Brachiopods also fall into this range.

Brachiopods are more closely related to Bryozoans than Mollusks. The easiest differences to identify are in the shells of clams, part of the mollusk family, and Brachiopods. Mollusk shells are divided into left and right while brachiopod shells are divided top (dorsal) and bottom (ventral). Mollusk shells are usually equal on the right and left. In brachiopods, the bottom shell is larger than the top. The other big difference is in how they feed: both are filter feeders, but mollusks extend their filter into the water and pull food into their shells. Brachiopods have internal feeding structures: water is drawn into the shell where the food is filtered out before expelling it out.