Kentucky State Fossil - The Brachiopod

In 1986 the Kentucky state legislature designated the brachiopod as the Kentucky state fossil.

During the Paleozoic Era, small, shelled animals called brachiopods were the most abundant, filter feeding organisms in Earth's oceans. While they superficially looked like clams and oysters they are entirely unrelated. These other shellfish are molluscs, but brachiopods occupy their own phylum, Brachiopoda.

Platystrophia brachiopod fossils from Maysville, Kentucky.
Platystrophia brachiopod fossils from Maysville, Kentucky.

Clams and brachiopods have a very different internal structure but one of the most visible differences is that the two halves of a brachiopod shell are not identical. The larger side of a brachiopod’s shell has a hole in it which a stalk protruded through to anchor the animal to the sea floor. There are still several hundred species of brachiopods alive today, though they aren’t the dominant filter feeder they were in the Paleozoic.

Fossil brachiopods are common in rocks throughout much of Kentucky and are the most frequently collected fossil in the state. Brachiopods in general were named as the state fossil rather than specifying a specific species as is the case with most states.