Obscure vertebral anatomy term of the day: bouton
October 25, 2022
Long-time readers will recall that I’m fascinated by neurocentral joints, and not merely that they exist (although they are pretty cool), but that in some vertebrae they migrate dorsally or ventrally from their typical position (see this and this).
A few years ago I learned that there is a term for the expanded bit of neural arch pedicle that contributes to the centrum in vertebrae with ventrally-migrated neurocentral joints: the bouton, which is French for ‘button’. Here’s an example in the unfused C7 of a subadult sheep. Somebody gifted me a handful of these things a few years ago, and I’ve been meaning to blog about them forever. Many thanks, mysterious benefactor. (I mean, only mysterious to me, because my memory is crap; I’m sure you know who you are, and if you ever read this, feel free to remind me. And thanks for the dead animal parts!)
Guess what? You have these things, too! Or at least you did; if you’re old enough to be reading this, your boutons fused with the rest of the separate bits of your vertebrae a long time ago, between the ages of 2 and 5 (according to Bagnall et al. 1977). Here’s a diagram from Schaefer et al. (2009: p.99) showing the separate centrum and neural arch elements in a thoracic vertebra of a human toddler. So, hey, cool, we all had boutons, just like sheep. And just like some sauropods. (You didn’t think I was going to do a whole OVATOD post without sauropods, did you?)
Here’s our old friend BIBE 45885, an unfused caudal neural arch (or perhaps neural ring) of Alamosaurus, which I’ve been freaking out over for five years now. Those fat bits of neural arch that very nearly close off the neural canal ventrally? Boutons, baby! Big, beautiful boutons. In this photo it looks like the paired boutons meet on the midline, but in fact they merely overlap from this point of view — there is a narrow (<1mm) squiggly gap between them. Given how narrow that gap is, I suspect the two boutons probably would have fused to each other before either of them fused to the centrum, if this particular animal hadn’t died first.
Here’s an unfused dorsal centrum of Giraffatitan, MB.R. 3823, which I yapped about in this post. This vertebra is the spiritual opposite of the Alamosaurus caudal shown above: instead of the neural canal being nearly enclosed by bits of the neural arch wrapping around ventrally, the neural canal is nearly enclosed dorsally by bits of the centrum sticking up on either side and wrapping around dorsally. As with the boutons of the Alamosaurus caudal, the two expanded bits of centrum stuff in this Giraffatitan dorsal approach each other very closely but don’t quite meet; you can fit a piece of paper between them, but not a heck of a lot more. In essence, those “two expanded bits of centrum stuff” are centrum boutons that project up into what I suppose we’ll keep calling a ‘neural arch’ even though it’s neither very neural nor an arch. Or perhaps anti-boutons? With apologies to Gould and Vrba (1982), here we have another missing term in the science of form.
Why do we, and sheep, and prolly lots of other mammals, and some sauropods, have boutons? Presumably to strengthen the neurocentral joints by expanding the joint surface area. I don’t know if anyone has ever tested that — if you do, please let me know in the comments.
Many thanks to Thierra Nalley, who may be the only person I know besides Mike who spends more time thinking about vertebrae than I do, for introducing me to the term ’bouton’ a few years ago. If for some reason you want to corrupt your sensibilities reading about primate vertebrae, you could do a lot worse than checking out Thierra’s papers.
I don’t expect we’ll have a ton of OVATOD posts, in part because there aren’t a heck of a lot of vertebra parts that we haven’t already blogged about. But who knows, maybe Mike will write about prepostepipophyses or something. Stay tuned!
References
- Bagnall, K.M., Harris, P.F., and Jones, P.R.M. 1977. A radiographic study of the human fetal spine. 2. The sequence of development of ossification centers in the vertebral column. Journal of Anatomy 124(3): 791–802.
- Gould, S.J. and Vrba, E.S. 1982. Exaptation—a missing term in the science of form. Paleobiology 8(1): 4-15.
- Schaefer, M., Black, S., and Scheuer, L. 2009. Juvenile Osteology: A Laboratory and Field Manual. Academic Press, Burlington, MA, 369pp.
P.S. Can we all pitch in and make ’bouton’ the new ‘aglet‘? Please? Please?
Skull audit: Wedel responds
February 9, 2022
Left to right: alligator, beaver, black bear, armadillo, cat, ostrich. I know, the archosaurs aren’t mammals, and the alligator isn’t even a skull. But if you can’t have a lounge lizard crash your mammal skull party, what are you even doing with your life? Not pictured: about four rabbit skulls I forgot I had boxed up, plus a couple of turtles (yeah, yeah) sitting on a friend’s desk, in their locked office.
It warmed my crooked little heart to see Mike Taylor, noted sauropodologist and disdainer-of-mammal-heads, return mammal skulls to the blog’s front page yesterday. Naturally I had to support my friend and colleague in this difficult time, when he may be experiencing confusing feelings regarding nasal turbinates, multi-cusped teeth, and the dentary-squamosal jaw joint.
My skull collection is split across home and office, but I had to go in to campus this afternoon for a video recording thing, so I got most of the office set, shown above, on that jaunt.
After the workday ended, I had just enough time before the light faded to assemble and photograph the home collection:
Back row: peccary, pig, deer, sheep, dog. Middle row: opossum, rabbit. Front row: opossum, marten (both hemisected). Not pictured: emergency backup sheep, moar rabbits
I’ve blogged about the bear, the pig, and the hemisected skulls, but I think that’s it. I should do more skull blogging, most of these have a story:
- I prepped the armadillo, cat, rabbit, and sheep skulls myself (besides the bear and pig). The first two I found in the woods, the mostly-decomposed rabbit was a gift from my father-in-law, and the sheep head I obtained from the market down the street ($10, and I ate the meat).
- The alligator head and deer skull were gifts, from Vicki and from my brother Ryan, respectively.
- The rest I purchased here and there over the years, usually when they were on deep discount. The peccary is a memento of a trip to Big Bend back in 2007 (I bought it at a taxidermy shop a long way outside the national park), and the dog came from the seconds bin at the Museum of Osteology — I plan to saw off the top of the braincase to see the cranial nerve exits, just as in the preparation by Peter Dodson shown in this post.
I have more heads awaiting skull-ization in various freezers, too. Couple more pig heads at work, and at the house a strategic reserve sheep head, plus skunk, squirrel, and rat. Plus a partially-mummified but mostly defleshed armadillo whose saga deserves a detailed recounting:
NB: the stray bits toward the bottom of the image are from a cat. Mr. Armadillo’s limb bones and vertebrae are still in the armadillo kit.
In the first comment on Mike’s post yesterday, I expressed envy that he had the better skull collection. After pulling together all my critters, I think I just have a worse memory. In my defense, it’s been almost two years since I was in the office regularly, and about half the skulls in the home collection are recent-ish acquistions (~last three years), so a lot of stuff had either fallen out of memory or not gotten properly established yet. But Mike has definitely prepped more — and more exotic — skeletons, and it was his enthusiastic collecting and blogging of dead animal bits that inspired me to start my recent-ish spate of skull preparations. More to come on that front as time and opportunity allow, probably starting with this:
Partial audit of mammal skulls
February 8, 2022
These are out as I consider how to reorganise my office.
The pig skull came from a hog-roast, and was very crumbly by the time I had prepped it out. It’s subsequently had an accident when it fell off a loudspeaker in my youngest son’s room, so it’s not the pig it once was. (I have a plate of pig-skull shards that I know full well I will never reassemble, but can’t quite bring myself to toss out). The sheep is of course a ram, the horns being the giveaway: shame the right horn is broken off at mid-length. The deer awaits reassembly.
I think all the carnivorans have featured here previously, with the possible exception of the emergency backup badger which I opportunistically harvested from a rotting roadkill about a year ago.
We’ve seen the wallaby and squirrel here, too. I think the rabbit has yet to put in an appearance, but we have more than enough rabbit stuff on this here sauropod blog so I’m not going to lose sleep over that.
Other mammals available to me: I have a rat, a hamster and a gerbil in various states of decay in plastic tubs in the woodshed. Come summer (since this is definitely an outdoor sport) I might see what can be done to get the skulls out of those. You will excuse me if I don’t go out of my way to extract a gerbil postcranium.
Three skulls in three dimensions
October 21, 2020
Get your red-cyan glasses — you do have some, right? — and check out this glorious image. Best full-screen it, it’s worth seeing!
And here is the lame 2D version for those of you who have still not spent 99 lousy cents on a pair of 3D glasses:
What are we looking at here?
Well, the smaller skull at bottom left is my new badger, which we saw a couple of days ago. Since then it has dried out, and I was easily able to figure out which teeth belong where, and glue them in with a drop of wood glue. I’ll photograph it in more detail at some point, but for those of you who can’t wait, there’s always the TNF of my first badger skull.
On the right is, if I’m not mistaken, a sheep — specifically a ram, given the horns. I don’t actually remember this one’s origin story, but it’s been sitting on a box next to our oil tank for a couple of years, with the flesh bits slowly decaying off and the bone cleaning itself up the way nature intended. A couple of days ago I cleaned it up a bit with my trusty toothbrush to remove some bits of moss and lichen, then soaked it for a few hours in very dilute bleach. It’s dried out beautifully, and is very robust. It’s big, too.
Everything else you see belongs to a deer — I assume, based on the horn bases. This is another one recovered from the depths of time. Some years ago, I put it a big water-filled pan and left it outside and forgot about it. In that time, not only had all the meat rotted off the bones, but the water had clarified and everything in it had died, so it didn’t even smell particularly. When I took the bones out, they were a nasty brown colour and little soft, and I thought I was going to have to discard them all. But once they had dried out they seemed a little more robust — though still brown. Then I left them overnight in dilute bleach, and when they had dried from that, they were their present much more appealing whitish colour, so I think they’re going to be OK.
Most of the cranium is intact in a single piece, though some of the sutures are wobbly and will need stabilising with wood glue. The mandible is in two parts, but both seem in decent condition. Right at the bottom left of the photo is a shard of bone by the tip of the mandible: this is the left nasal, which flaked off, but should be repairable. Everything else is vertebrae: atlas right behind the skull, axis by the snout, C3 just above it, and damaged C4 just below the atlas.
When it’s been put together a bit more, I will post some better photos, and I’ll see if anyone can identify the species.
Sauropod Vertebra Picture of the Week 