Going by the fossil example shown on the Pennsylvanian Atlas of Ancient Life, I am calling this find a Pseudorthoceras. The rock was split into two pieces, and the photo is of them joined back up. The white markings are from an air scribe.
![](https://fossil.15656.com/wp-content/uploads/2019/04/FA137BE4-1C13-47CF-B356-95A1BB1C2B07-1024x407.jpeg)
Pseudorthoceras belongs to the class Cephalopoda. Mooreoceras can also be found in the local rocks and could also be what this particular specimen is.
Pseudorthoceras