Mastodon in Traverse City?

Today in the news: Possible mastodon carving found on rock in Grand Traverse Bay. The Traverse City Record-Eagle included this caption with the picture above: "Mark Holley explains what he thinks is an ancient carving of a mastodon carved into a rock recently found in 40 feet of water in Grand Traverse Bay. The red lines follow etchings made in the rock, he said."

This is interesting because Mastodons didn't live that far north (or so we've always thought) and because it's underwater. I wonder how they're going to get petroglyph experts, who usually aren't divers, to examine it?

Compare the Mastodon to the Sanilac petroglyps near Bad Axe:

















I have no idea what the petroglyphs depict, but to me the Mastodon does look similar.