Help identifying leaf-like bone
Those are isolated turtle bones:



Specifically, they are part of the carapace, or upper shell. The projections would articulate with the backbone. The "toothlike" structure at the other end projects down toward the margin of the shell.

Based on the size, and the fact that you are in Missouri, I'm guessing they are snapping turtle bones. Here's a photo of the inside of a snapping turtle shell:



They are a little hard to make out, but you can faintly see the marginal projections.