Tiny Pennsylvanian Ammonoids

[connorp]

Over the past year I've I found two tiny ammonoids from a site in the Carbondale Formation (Middle Pennsylvanian) of Illinois. Both measure approximately 5mm in diameter. The first specimen below showed no details of the exterior of the shell, which I believe are necessary in identifying these.

 

 

This week I found a second specimen (maybe a different species) which does show the suture pattern. I'm hoping that this specimen is identifiable.

 

Part

 

Counterpart

 

Does anyone recognize the species? Thanks!

[Rockwood]

Cast an clear artificial matrix slab on to it and prep it from the other side.