Last Friday I gave you this skull to identify:

There was strong consensus on this being a mustelid – which is good, because that’s what it is. There was also good agreement on it being one of the Martens, which is where things become a bit more difficult.

After looking at a lot of different Marten skulls online without much success in finding a way of telling them apart, this diagram  proved quite helpful.

Skulls in the sequence: M. zibellina, M. martes, M. foina

If you look at the skull in the middle of the top and centre rows, the auditory bullae (the rounded bones under the skull that house the anatomy used in hearing) have quite distinctive shapes in the three species pictured.

In addition, the the little nub of bone (called the mastoid process) that sticks out behind the ear hole (or external auditory meatus as it’s also known) is very differently developed in the three species. Looking at this character and checking back against other Marten skulls online the clues suggested that the mystery object is the skull of a Pine Marten Martes martes (Linnaeus, 1758).

So well done to everyone who commented – particularly Jake who got the ball rolling with a Martes identification from the start!