Next time your son or daughter asks which kind of dinosaurs lived in Indiana millions of years ago, you can smile thoughtfully and say, “We really don’t know.” Sigh. It’s true. When it comes to dinosaurs dating to the Mesozoic or earlier, Indiana doesn’t have much to brag about in either fossils or knowledge, but when it comes to brachiopods and mastodons (clams and wooly mammoths), the Hoosier state rules…
In the Paleozoic Era (approximately 250 million years ago), a shallow sea covered Indiana, depositing an abundance of brachiopods, crinoids and trilobites. Large reefs systems covered the state as well, sometimes trapping organic matter to later become petroleum deposits.
Indiana isn’t known for its dinosaurs, but not because they didn’t live here. Between the Paleozoic and Mesozoic Eras, the shallow sea covering Indiana constantly eroded the bedrock. Any material that could have contained fossils was worn or washed away.
When the Potawatomi discovered the fossilized remains of wooly mammoths around Devil’s Lake (Lake Manitou in Rochester), they assumed the massive, odd creatures were the remnants of water monsters, earning the lake its forbidding name.
Lake Chicago, a massive glacier that covered northern Indiana and helped form the Great Lakes, is largely responsible for Indiana’s current topography (flat in the north, hilly in the south). 13,000 years ago the glacier retreated and eventually transformed into Lake Michigan.
The abundance of plant fossils discovered in Indiana (almost 150 species) have given them status as trace fossils, used to date prehistoric coral seams at other sites.