Hello all,
I don't know much about cephalopods and really could use your help.
I found this small rock with the tiny nautiloid specimen in the banks of the Rock River in Ogle county, Illinois. The area's bedrock is Middle Ordovician (Mohawkian, Ancell Group).
I believe it belongs to the order of the Actinoceridae. The "camerae" end in double pointed arches instead of a straight edge, just as Wikpedia's illustration shows in the 2nd pic below.
What seems to be unusual in my specimen - can't find any photos of this anywhere - are the rounded camerae, vs the tightly lined-up straight banding on other specimens. (I'm not sure about the correct terminology...sorry).
If I'm not totally off base, is there a chance to narrow down the ID further?
Thanks in advance.
General form of Actinocerid: