Friday mystery object #419 answer

Last week I gave you a genuine mystery object from an archaeological dig in Dublin to have a go at identifying:

There were several suggestions, both in the comments here and on Twitter. They can’t all be right, so this seems like a good opportunity to look at the skulls of a variety of different species, so we can narrow it down.

Scale is important in this, since the mystery object is quite large, despite being just a section of the braincase from the rear of the skull, made up of parts of the parietal bones (on either side) and part of the occipital bone (the bone that forms the back wall of the skull). This is an area of convergence on the skull – a meeting point for the bony sagittal crest associated with attachment of the temporalis muscles (used in operating the jaw) and the nuchal crest associated with the nuchal ligament that connects the trapezius muscles of the neck (used in moving the head) to the skull.

1. Deer.

Deer skull
Deer skull

Cervids lack the well-developed sagittal crest seen in the mystery object. They also have a broad triangular scar for the attachment of the nuchal ligament – presumably relating to the high forces that the nuck muscles have to deal with due to the carrying of and fighting with antlers. In females the shape of the nuchal scar is very similar, although it’s less well defined. So the mystery, with its strong sagittal crest and neat occipital crest is not from a deer.

2. Bovids.

Sheep, cows and other bovids are similar to deer – with a broader nuchal scar (presumably for similar reasons to the deer). Their reliance on masseter muscles more than the temporalis muscles when chewing also means that their sagittal region doesn’t match our mystery critter, with the temporalis scars usually not meeting the midline of the skull:

Sheep skull

2. Pig.

In profile the pig skull looks like a pretty good match, with scars from quite well-developed temporalis muscles just behind the eye socket:

Pig skull

But the Suidae actually have a very distinctive spatulate shape to the rear part of their skulls, presumably for incredibly hefty nuchal ligament attachment to help power their rooting activity:

Pig skull

That results in a very distinctive shape in the dorsal view, so the mystery object is clearly not a pig:

Pig skull

3. Horse.

Horses can have a fairly well-developed sagittal crest and I don’t feel like I can entirely disregard the possibility that this mystery specimen may be from a mature Equid, although the shape looks somewhat off to me – a bit flatter and angled more downwards:

Horse skull

The horse specimens I’ve seen also have more of a nuchal ‘knot’ rather than a defined ridge in the midline of the occipital:

Horse skull

4. Camel.

Camels have very strongly developed sagittal crests, but this is parly due to the short and narrow area to the rear of the braincase, so the crest rises sharply. The nuchal crest is also much more prominent, forming a continuous sharp line right into the zygomatic arch:

Dromedary camel skull

The mystery object could be from a camel, but I think it lacks the strength of the camel’s nuchal region and the braincase seems broader than that of the camels.

5. Badger.

There was a suggestion of badger, but that can be ruled out simply because of the size. This section of mystery bone is about as long as a badger’s entire skull:

Badger skull

While the size is off, the suggestion does have merit in terms of morphology, as the broad braincase does hint at a member of the Carnivora and in Ireland there aren’t many large carnivores – at least not any more.

6. Seal.

One type of large carnivore still found around Ireland would be the seals. However, the need for extreme flexibility in their head movements while resisting drag from their watery environment gives them a very characteristic shape to their nuchal region:

Seal skull

7. Dog.

Dogs are always worthy of consideration in these instances. They can be small or large, their skull shape can vary hugely and they are found everywhere that humans are found.

Dog skull

This does seem a bit more like it, although size is still an issue. Even the biggest dog – and the skull shown above is from a BIG dog – struggles to be close to the right size. Also, the nuchal crest in dogs tends to taper to a point fairly evenly, whereas the mystery bone has a nuchal crest that has ‘shoulders’ for want of a better term. Dog is possible, but I’m not convinced.

8. Cat.

There is no way a domestic moggie could come close to big enough, but there are big cats that come surprisingly close:

Tiger skull
Tiger skull

The nuchal crests of lions and tigers have those ‘shoulders’ and a well defined occipital crest down the midline. They are also closer in size and the braincase and sagittal crest are about right.

9. Bear.

Of course, we can’t talk about lions and tigers without also considering bears.

Bear skull

Again, the nuchal crest ‘shoulders’ are there, the size is perfect and the sagittal crest and braincase are close. However, the occipital crest seems a little less well-defined.

So these are the species I’ve been considering and at the moment I’m thinking big cat or bear for this mystery object. I know there are other large carnivores, like hyenas, but they have an unmistakable sagittal/nuchal region:

Hyena skull

I will need to have the specimen in my hand with a good range of comparative specimens available to get a more conclusive identification. One significant factor will be that as animals mature, their muscle scars tend to become more rugged and this changes their appearance, so I will need specimens from animals of different ages and life histories to help consider those factors.

Sorry I’m not giving you a definitive answer this week, but I hope you’ve enjoyed the process!

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