This is in Tulsa Oklahoma, on a 5 acre park-like property. Lots of grass and trees and a large pond nearby. I'm 99% sure I know what it is. Scales are rough. I don't know where the poor things other half is, I have no idea what happened to it, it's on fenced private property, but it looks like a clean shovel separation...but I sure didn't do it. I have a lot of garters, rats, racers, but this is a first for this guy. Thanks for the id.
https://postimg.org/gallery/1tei77ry0/