For the (fossil) record: Database gives insight into Minnesota’s prehistoric past

If you’re hoping for a good read on dinosaurs in Minnesota, this isn’t it. There’s scant evidence so far — one fossilized dino claw found in 2015, a chunk of vertebrae and a tooth — that these extinct reptiles roamed our state.

But the other kinds prehistoric, fossilized animals found in Minnesota might surprise you. Long before humans ever called this state home, there were coral, sharks, woolly mammoths, antique bison and hundreds of other species, many now extinct, here.

That’s according to the Paleobiology Database, a project being developed at the University of Wisconsin-Madison. The data is being compiled by researchers far and wide from published accounts of fossil findings, and contains more than 2,600 fossil entries in Minnesota. You can explore the Paleobiology Database at length here, but to save you time, here’s what we learned about early life in Minnesota.

Under the sea

Ahoy! For much of Minnesota’s history, its modern residents wouldn’t recognize it. The state was mostly or completely underwater as part of the continent Laurentia, pretty near the equator, for millions and millions of years: certainly no place for winter sports.

In the Cambrian era, Minnesota was part of the continent Laurentia, which was largely under water.

That helps explain the prevalence of so many marine fossils in Minnesota.

“We see a variety of ocean life here then in different stages, especially the limestone formations along the Mississippi in St. Paul,” said John Westgaard, project lead for the Hill Annex Paleontology Project who works with the Science Museum of Minnesota.

Documented Minnesota animal fossil finds by phylum
Fossils in the database were gleaned from published papers and do not represent all fossils ever discovered in Minnesota. Finds may represent multiple animals found in one spot. Hover over chart for descriptions of phyla/animals included in phyla.

Westgaard is currently working about a hundred feet below the surface of the land in a pit mine at Hill Annex Mine State Park, near Calumet on the Iron Range, excavating fossil, plus sifting through materials excavated from the pit.

From "Minnesota's Geology," 1982, University of Minnesota Press. Used with permission.
In the Devonian age, between 416 million and 358 million years ago, only the Southeastern corner of Minnesota was covered in water. The dashed line illustrates the equator.

The first Minnesota fossils in the Paleobiology Database are from the Cambrian Period (540 to 490 million years ago). This period is associated with warming temperatures and rising sea levels that pushed water onto land masses, creating shallow habitats for marine life, according to National Geographic. This, it’s believed, spawned an explosion of life forms, including early chordates, which eventually came to include humans.

But long before our species evolved, fossil evidence shows a lot of the animals hanging out in Minnesota for millions and millions of years, past the Cambrian and into the Ordovician and Devonian periods, were squirmy marine critters, including trilobites (arthropods), relatives of crabs and lobsters, mollusks, relatives of snails, corals and other small marine animals.

Tyrannosaurus rocks

OK, now we’re at the really sad part of the Minnesota fossil story.

Our neighbors in the Dakotas have them. How can we explain the scarcity of dino evidence in Minnesota?

Dinosaur fossils are found in rock, and there’s not much rock from the age of the dinosaurs in Minnesota and Wisconsin, said Mark Uhen, a professor at George Mason University and the executive committee chair of the Paleobiology Database.

“So there’s two options. The rocks were deposited and then later receded, or they were never deposited,” he said.

If the rocks were deposited and later removed, massive glaciers that meandered down from Canada, leaving the lakey terrain we know and love, might be to blame.

As for the dinosaur claw, some of the most convincing evidence dinosaurs lived in Minnesota, which was spotted at Hill Annex Mine State Park in 2015, it’s unclear whether its owner lived here or if the claw was dragged here by glaciers or some other mode of transportation.

At any rate, the dinosaurs were extinct at the end of the Cretaceous period and other interesting animals would soon appear in what was shaping up to be the Land of 10,000 Lakes.

Mammals, reptiles

During the Cenozoic era (66 million to the present), known as the “age of mammals,” glaciers raked across the surface of Minnesota, and new mammals and reptilian life lived along their edges.

“Most animals would have been here living in Minnesota near the edge of the ice as it ebbed and flowed,” Westgaard said. “In between each of those glaciation periods, the animals would have been following the ice edge back up into Minnesota.”

This is the time period when the woolly mammoths enter the scene. The Paleobiology Database includes 14 of them, including bones found near Cedar Lake and a skull found on a soybean farm in Southern Minnesota, which is now restored and on display at the Science Museum of Minnesota.

Also notable is the discovery of Bison antiquus bones, an ancestor of the modern Bison bison, in Crow Wing County.

Courtesy of the Science Museum of Minnesota
A Bison antiquus skelton on display at the Science Museum of Minnesota

The findings have yet to be published, which explains why they’re not in the database, but a southern Minnesota cave recently yielded the bones of a homotherium, a big Ice Age lion, Westgaard said.

“If I’m not mistaken, there were also some sloth, horse and camel parts there as well,” he said.

In 1967, the skull of an ancient species of crocodile was discovered in an open pit mine near Coleraine. Cretaceous sharks and the remains of other large swimming reptiles like the mosasaur have been found, too.

CC/Wikimedia Commons/FunkMonk
Artist’s rendering of a mosasaur

“We have a nice variety here in the state, from some of the oldest stuff — the Cambrian and Ordovician that’s hundreds of millions of years old, to the Cretaceous to the Ice Age,” Westgaard said.

If you want to learn more about what he and others are finding at the Hill Annex Mine site, they’ll be exhibiting in the Education Building at the Minnesota State Fair this year, Westgaard said.

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