What the hell is this?

Tonight, I'm playing Rock Band 3 with the lady, and Timmy just starts barking his fool head off, facing the french doors which go from man cave to the outside.  I finally paused the game, and looked, but didn't see anything.  So, I leashed him up and we went outside.  He went directly to this thing, which was standing up on it's rear.  I thought it was just a leaf, and couldn't understand his trepidation towards it.  He would go towards it, then recoil quickly.  I kicked it with my foot, thinking it was just a leaf, but it had a more solid feel to it.  So, I went over and picked it up.  I can guess it's a skull, but I'm not sure what of.  Also, I'm not sure how it got there.  It's not a fresh kill, so would an animal be carrying it for the hell of it?  If so, what kind of animal?  Cat? Dog?  Coyote (never seen one in my neighborhood, but there are supposedly some around).  I'm guessing this is a possum skull.  There doesn't seem to be a spot for a jawbone, and doesn't resemble any skulls I could find online.  Perhaps it's not a skull at all?  Maybe a vertebrae?  If it's a vertabrae, is it large?  If my pictures suck too much for someone who may know what this is, let me know and I'll get a high resolution shot. 

Now, I'm not one to put much stock ghosts, spooks, boogers, haints, banshees or any manner of spectral nonsense, but for some reason, I don't like the idea of keeping it in the house.  If all else fails, I'll take it to the vet on Saturday.

Any thoughts?