This is certainly an interesting find but has me rather perplexed! It's not mastodon/mammoth; their teeth are like softball-sized molars. This reminds me more of a shark tooth with that darker crescent band along the top of the tooth and flattened back with sharp edge coming to a point. However, prehistoric sharks did not inhabit the shallow seas that once covered the Great Lakes region. So if it is a shark tooth, it did not originate here.

Also, I'm in no way an expert in tooth identification, especially fossil teeth and I don't believe we have any experts in this field available on this platform.

I might suggest emailing these pictures to Michael Gottfried, a professor of Vertebrate Paleontology at MSU. He studies fossil fishes and sharks, so he will hopefully be able to provide some better expertise.

Associate Professor
309 Natural Science
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I'm personally curious what you discover, so if you don't mind emailing me what you find, I'd greatly appreciate it (<personal data hidden>).

Thanks and hope this helps!