Prehistoric Animals of Michigan

The woolly mammoth (Mammuthus primigenius), or tundra mammoth.

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First, the bad news: No dinosaurs have ever been discovered in Michigan, mainly because during the Mesozoic Era, when the dinosaurs lived, the sediments in this state were steadily being eroded by natural forces. (In other words, dinosaurs did live in Michigan 100 million years ago, but their remains didn't have a chance to fossilize.) Now, the good news: This state is still notable for its fossils of other prehistoric life dating from the Paleozoic and Cenozoic eras, including unique creatures such as the woolly mammoth and the American mastodon.

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Woolly Mammoth

woolly mammoth on tundra

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Until very recently, very few fossils of megafauna mammals had been discovered in the state of Michigan (with the exception of some prehistoric whales and some scattered remains of giant Pleistocene mammals). That all changed in late September 2015, when a surprisingly extensive set of woolly mammoth bones was unearthed under a lima bean field in the town of Chelsea. This was a truly collaborative effort; various Chelsea residents joined in the dig when they heard the exciting news. In 2017, researchers from the University of Michigan discovered 40 additional bones and bone fragments at the same site, including parts of the animal's skull. Scientists also collected sediment samples, which they used to help date the fossil. They believe it is more than 15,000 years old and was hunted by humans.

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American Mastodon

mastodon skeleton in musem

Ryan Somma/Wikimedia Commons/CC BY-SA 2.0

The official state fossil of Michigan, the American mastodon was a common sight in this state during the Pleistocene epoch, which lasted from about two million to 10,000 years ago. Mastodons—enormous tusked mammals distantly related to elephants—shared their territory with woolly mammoths as well as a wide assortment of other megafauna mammals, including plus-sized bears, beavers, and deer. Sadly, these animals went extinct shortly after the last Ice Age, succumbing to a combination of climate change and hunting by early Native Americans.

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Prehistoric Whales

Sperm Whale and Calf, Portugal
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For the past 300 million years, most of Michigan has been well above sea level—but not all of it, as evidenced by the discovery of various prehistoric whales, including early specimens of still-extant cetaceans like Physeter (better known as the sperm whale) and Balaenoptera (the fin whale). It's not exactly clear how these whales wound up in Michigan, but one clue may be that they're of extremely recent provenance, some specimens dating to less than 1,000 years ago.

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Small Marine Organisms

Michigan's famous "Petosky Stone" is made of ancient coral

David J. Fred/Wikimedia Commons/CC BY 3.0

Michigan may have been high and dry for the last 300 million years, but for over 200 million years before that (starting in the Cambrian period) the area of this state was covered by a shallow ocean, as was much of northern North America. That's why sediments dating to the Ordovician, Silurian, and Devonian periods are rich in small marine organisms, including various species of algae, corals, brachiopods, trilobites, and crinoids (tiny, tentacled creatures distantly related to starfish). Michigan's famous Petoskey stone—a type of rock with a tessellated pattern, and the state stone of Michigan—is made of fossilized corals from this period.