I found this along the river. Assuming it came down from the Bearpaw Formation. My question is regarding the edge of the fossil. I think it is a piece of ammonite but the outer edge is creased. I have been reading that some Ammonites have a keel but all examples I have found look symmetrical. This one is creased on one side and does not look symmetrical at all. Could it have been damaged and flattened that way during fossilization? The nacre on the outside looks like the animal grew this way.
What do you think is going on here? Is it a piece of an ammonite or maybe something else?