Luckily, the curator was there and she told us it was a Devonian Period arthrodire (armored fish). They make great displays once there in 3-D form (http://www.palaeocritti.com/dunkleosteus-terrelli). I believe there is one in the lobby at the Falls of the Ohio State Park visitor center.
If I had to guess, this fossil probably came from the Cleveland Shale (member of Ohio Shale). It is probably a Dunkleosteus.
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhFb2nIfoDFkvYezLk_Xnk8sxhjMqVktlMWFWgDg67OkWibM-N2wJsAsYFE7zbA7nUgseRBjTt8dkIcVWK3By4zJpwIdhHPBX-XdUoryox6xuou42xhwA6dQQOECsARt2t6gcRZoH8XYGgD/s400/arthrodire-devonian-fish.jpg)