Conodonts: Microfossils of Distinction (PA-06)
Conodonts, microfossils in sedimentary rocks in ancient sea bottoms, are common in Indiana. Because they changed and differed from one geologic time interval to another, they aid in determining the age of sedimentary rocks. Acid-resistant and small, they can be the only fossil readily recoverable from drill holes. This makes them useful in oil and gas exploration.

First described in 1856, they are still a mystery. Fossil impressions of strange animals found recently in Montana contained groups of conodonts. They appeared to be embedded in the digestive organs of a small, primitive marine animal. Five or six kinds of conodonts were present in one individual.

Our Hoosier State Beneath Us: Paleontology