Your formation is older. It would be equivalent to the Lodgepole formation which is part of the Madison group in Montana. I also have some Productids from that formation too.
The examples of Echinoconchus I saw were from Kansas coming from Penn age rocks.
The productids in the original post are from the Kibbey formation which is Chesterian late Mississippian.
All of the brachiopods on the plate are produtids. They can grow to a large size. The bachial valve on the younger ones start out flat but then become convex. I have only seen spines on the pedicle vales, never seen the bachial valve. These guys are very fragile. It is likely they are Echinoconchus. I tend to be conservative on identifying brachiopods.
I have a two more plates I am working on now. I collected them yesterday.