Mystery bone (not a skull after all!)

Mystery bone (not a skull after all!)

Observation - Mystery bone (not a skull after all!). Description: Bone washed up on the Isle of Wight. About 9cm long. Looked like a fish-skull of some sort, but I had no idea what - see below for what it actually is.

Bone washed up on the Isle of Wight. About 9cm long. Looked like a fish-skull of some sort, but I had no idea what - see below for what it actually is.