Work of Animal or Man?

[romeo-1]

Found this morning in the mud on a tidal. Without going into the history of the area could this have been worked by man? Animal i'm sure but the shape looks purpose made...

 

[The Grim Reaper]

Looks like a Deer Jaw Bone that has been gnawed on by a rodent. Not man made.

 

[rock]

It would look good in a frame with other finds for decoration and a good study piece.