That is a convincing photo, I layered it in photoshop and you can see the eye still in the socket. I believe major damage was done to this reptile and have colored it to show what I believe to be the part ripped away from its mouth.
They are on two separate pictures but the artifacts are in the same vicinity
The first is the fossilised reptilian head located in picture Reptilian Head
http://mars.jpl.nasa.gov/msl-raw-images/msss/00021/mcam/0021MR0026006000E1_DXXX.jpg and for clarity a superimposed picture
And its Claw located in http://mars.jpl.nasa.gov/msl-raw-images/msss/00021/mcam/0021MR0026001000E1_DXXX.jpg - although scale wise the claw is probably too big for the reptilian
You can also just see them in Sol 003 picture 0003ML0000022000E1_DXXX.jpg although the clarity is not as good
