Fossil size: 1" to 1.5" across
Matrix size: 2" to 2.5" across
These are nicely preserved brachiopod (Platystrophia ponderosa) fossils from Kentucky. They come from the Mount Auburn Formation and are Ordovician in age or approximately 450 million years old.
Brachiopods are marine animals that have hard "valves" (shells) on the upper and lower surfaces. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection. In a typical brachiopod a stalk-like pedicle projects from an opening in one of the valves near the hinges keeping the animal anchored to the seabed but clear of silt that would obstruct the opening.