Indiana's fossil fusulinids (PA-16)
No larger than a wheat grain, spindle-shaped, with a calcium carbonate shell describe fossils called fusulinids. Cousins of the modern amoeba, fusulinids are extinct shelled protozoans that lived between 234 and 315 million years ago.

Several genera are found in marine limestones and shales in the coal-bearing strata of southwestern Indiana. Each genus has its own identifying internal architecture and is a key to the identification and age of its own rocks.

Fossil fusulinids help geologists in Indiana to correlate isolated rock exposures, to identify subsurface rocks, and to coordinate local geologic history with events in the worlds geologic history.

Our Hoosier State Beneath Us: Paleontology