Which bone is it ?
The point where the skull had broken made it much more difficult to identify, because it wasn't possible to know the exact length of the skull, or check the teeth, which are really useful for identification:
Here's the other side with a scale bar:
I could also tell it was from a mammal, not a bird, because of the rough feel of the bone, and similarities to other skulls I had. For example, a few mammals, from cats to squirrels, have those triangles of bone above the eye socket at top right.
How big was it ?
Most guides to skull sizes are based on adult skull sizes. Was this an adult ? I thought so because underneath the skull, the central part was smooth. In other mammals, there are two horizontal unfused lines in very young animals, one in young adults, and none in older animals.
Where was it found ?
What bits looked like other animals ?
Animals are grouped into families, which really means close relatives. A domestic cat skull looks a lot like a lynx or puma because they are from the same family of felids, even though they live quite different lives. The same is true of beavers and mice, which have similar skulls but are massively different sizes, because they are in the rodent family.
So if this skull looked a bit like another skull I had, they might be related, even if they were different sizes.
One thing that was distinctive was the Y-shaped ridge between the eye sockets and the middle line of the top of the skull:
Working out the family
Looking a bit like a badger and a bit like an otter doesn't sound very useful unless you know that badgers and otters are from the same family: mustelids, which I'd thought when I first saw the mystery skull. The mustelid family is not very big, and in the UK that would include badgers, otters, pine martens, stoats, mink and weasels. Oddly enough, when I put the mystery skull next to my beech marten skull earlier, they didn't look very similar because beech martens don't have the ridge at the back of the skull, or the Y-shaped ridge above the orbits.
Here's the mystery skull next to (L-R) my beech marten, otter, and badger:
Working out an exact size
Dad helped me with some of the maths on this.
If the mystery skull was the same proportion as the otter, as seemed likely, and I knew the length of the mystery skull portion, and I knew the percentage of the equivalent portion of the otter skull, I would be able to work out the entire length of the mystery skull.
My otter skull is 12.5cm long, and the part from the back to the spikes above the orbits was 8cm. So the length of the part of the otter skull from the eye spikes backwards was 8/12.5 = 64% of the length of the skull.
The same part on the mystery skull was 44mm long. So if 44mm is 64% of the skull, then the entire skull would be 69mm long, if the proportions would be the same as the otter.
Skullsite.co.uk gives these lengths of skulls for the smaller mustelids:
- Ferret: 67mm
- Pine marten: 76mm
- Mink: 60mm
- Weasel: 40.4mm
- Stoat: usually over 42mm
So it looked most likely to be pine marten, ferret, or possibly mink, but not weasel or stoat.
Pine marten, ferret or mink ?
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