The Internet is for cat photos. Here are mine.

September 17, 2015

Regular readers will remember that I recently fished my cat skull out of the tub where invertebrates had been hard at work defleshing it, and put it to soak — first in soapy water, then in clean water, and finally in dilute hydrogen peroxide. It was in a pretty terrible state, having either been smashed by a car, or damaged by my rather unsophisticated process of removing the head from the torso. Here’s a reminder:

IMG_1977

After bleaching in H2O2, the skull parts looked much better, but were still very delicate. Here is the main portion of the cranium, missing the braincase and the right upper jaw, upside down, in right posteroventral view.

IMG_1979

Putting it back together was difficult. I am using regular water-soluble wood glue, largely so that if I make a mistake I can just soak the wrongly-joined bits apart and try again.

I started by gluing the braincase (at the top of the plate in the first picture) onto the back of the main cranium piece. Unfortunately, as you’ll see below, I wasn’t able to get a very clean join — I can only assume that one or other part was slightly distorted by whatever force broke the skull apart. Still, having done that, I had a better platform to reattach the right upper jaw (lower left of the plate). I was then able to reattach the broken-off part of the right zygomatic arch (at about 4 o’clock on the plate, just to the right of the lower of the two dentaries, and below a vertebra). It didn’t fit quite right, but what can you do? FInally, I was able to reattach another small piece — at 6:30 pm on the plate — which I think is part of the left auditory bulla.

That gave me a workable cranium (though I have some bits left over — see below.) It was time to repair the right dentary. Its articular cylinder (not really a condyle, despite its name) had somehow got blasted off, as had its retroarticular process: it was quite satisfying to figure out how those Shards Of Mediocrity fitted onto the main part of the dentary.

With that done, I had to glue together the two dentaries. That’s hard to do: it’s awkward to brace them in position for the glue to set, and difficult to get the angle between the two bones correct so that the two articular cylinders both sit neatle in their receptacles in the cranium. Here’s the solution I came up with:

IMG_1987

I rested the cranium upside down, covered the jaw with some thin, pliant plastic (actually a sandwich bag) and used the cranium itself as a perfectly proportioned brace to hold the dentaries in place. Then I was able to glue them more or less correctly, and to reinforce the joint with more glue once the first lot had set.

I’ve still not got it quite right — the mandibular symphysis is wonky — but I think it will do. And if I change my mind, I can always soak the mandible apart and try again.

(As a matter of fact, I’d already done that once, having initially glued the dentaries together at the wrong angle, so that the assembled mandible was too narrow, and wouldn’t articulate properly with the cranium.)

So now I have a pretty good mandible and cranium, as well as the first five cervical vertebrae (all but one of the postzygs of C5, which was lost in the head-removal process.) Here is the whole thing, put together, in dorsal view:

IMG_1989

(You can see where the left zygomatic arch is damaged: the bones are not articulating correctly, as they do on the right.)

And here is the same assembly in left dorsolateral view:

IMG_1990

And finally, the skull in anterodorsal view:

IMG_1993

Note that the left canine is truncated. I am completely certain that this, at least, is not my doing, and must be damage that was done in life. Note, too, how the mandible is visibly wonky from this angle. Hmm. Maybe I will reset it again.

At the end of this process, I have a pretty nice cat skull. Unfortunately, I have seven shards left over, none of them more than about fifteen millimeters long. Here they are:

IMG_1997

I’d welcome any help in figuring out what these bits are, and where on the skull they should be reattached. I don’t want to just throw them away. Click through for much higher resolution to get a better idea of what’s what. The top right piece is such a weird shape that someone must know what it is. The two peices at bottom right seem to be pairs, but I don’t know what they are a pair of. The rest? No idea.

I leave you with the dorsal view again, but this time in glorious 3D for those of you who have been wise enough to get some red-cyan 3D glasses. (Seriously folks, they’re like fifty cents a pair. Just get some. You won’t regret it.)

cat-skull-dorsal-view-anaglyph

Some time soon: those first five cervicals in more detail.

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11 Responses to “The Internet is for cat photos. Here are mine.”

  1. dmaas Says:

    nice!
    Make roundabout photos and I’ll ‘gammetrize it for you!

  2. Mike Taylor Says:

    Thanks, David! I appreciate the offer, but I think this skull is too smashed up to warrant that treatment (at least unless I figure out how to reattach the fragments. I hope to have a better cat skull soon, though.

  3. Matt Wedel Says:

    The paired elements are almost certainly the missing nasal bones, which would fill in the top of the inverted-V-shape of the current nasal opening. The hook-shaped bone on the upper right of your leftover bits photo is the pterygoid process of one of the sphenoids. I’ll send you pictures of my own cat skull – which I found out in a cow pasture in Oklahoma – so you can see where it fits.

    To ID the rest of the bits you’ll probably need to have an intact skull on hand to compare with. Nice job getting this one back to together – when I saw the pile of pieces I was not terribly optimistic.

  4. Mike Taylor Says:

    Nasals were my first thought. I just can’t see how to fit them in, though. I’ll have another go tonight.

    Good news on the sphenoid, though: I’ve found where it (more or less) fits. Thanks!

  5. Allen Hazen Says:

    Thought on gluing the dentaries back together. Problem: holding them together in just the right position while the glue dries. Ideal but unobtainable solution: an arrangement of clamps that can be adjusted to arbitrary positions and angles. Possible (I haven’t tried this, it’s just a thought that occurred) way of approximating to said solution: lump of modelling clay — insert the unglued end of the bone into the clay deep enough to hold it steady, add glue and press unglued end of other dentary into clay in such a way as to hold it at the desired position and angle.
    ???

  6. Mike Taylor Says:

    Yes, I wondered about using plasticine, but then I worried about its oils leeching into the bone and discolouring it. As it turned out, bracing the mandibles in the cranium itself was pretty good.

  7. Mike Taylor Says:

    Yes, they’re nasals. The breakthrough came then I stopped trying to fit them into the nasal aperture, and instead just looked at how the two of them went together. They very very nearly into a single unit, and once I’d glued that symmetrical unit together, it was very obvious how to fit it into the skull. I just glued it in place now (admittedly with some minor damage to the RTs).

    This is good — I only have four pieces left. I’m pretty sure at least some of them make up the right auditory bulla, but I can’t for the life of my figure out how. Not yet, anyway.

  8. John Scanlon Says:

    The symphyseal surfaces are usually a bit convex (it’s an intermandibular joint, not really a symphysis if they’re not fused) so it’s best to clamp them _lightly_ when gluing; that way the mandibles are held in place mainly by the jaw joints and tooth interlock. A plastic clothes peg can work well for this; I’ve used them recently for cat and also small macropodid mandibles.

  9. Mike Taylor Says:

    Thanks, John, useful advice. I will probably redo the mandible. It’s not bad how it is, but it’s not right.


  10. […] process of reassembling my cat skull continues. I now have the sphenoid and both nasals now back in place, and the time has come for the […]


  11. […] I separated my cat’s head from its body, the first five cervical vertebrae came with it. Never one to waste perfectly good […]


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