Some quick backstory: lots of sauropods have long, overlapping cervical ribs, like the ones shown here in Sauroposeidon (diagram from this old post):

These long cervical ribs are ossified tendons of ventral neck muscles, presumably longus colli ventralis. We know they’re ossified tendons because of their bone histology (Klein et al. 2012), and we suspect that they’re longus colli ventralis because those tendons look the same in birds, just less ossified, as in this rhea (same specimens as these even older posts: 1, 2):

Diplodocoids have apomorphically short cervical ribs, which never extend very far past the end of their respective centra and sometimes don’t overlap at all. Still, we assume the long ventral neck muscles were there, just without long ossified tendons. Which brings me to Apatosaurus, which has cervical ribs that are anteroposteriorly short but famously massive, extending very below and/or to the sides of the cervical centra — for a truly breathtaking example see this post. Here are C3 through C7 in CM 3018, the holotype of Apatosaurus lousiae (Gilmore 1936: plate 24):

At least for me, it’s hard to resist the temptation to mentally scoot those vertebrae together into articulation, and imagine that the very swoopy-looking and maybe even down-turned cervical ribs allowed the ventral tendon bundles to wrap around the bottom of each cervical rib protuberance, something like this:

But it’s just not so, because like all 2D images, Gilmore’s plate distorts 3D reality. If you get to see the mounted skeleton in person, it’s clear that the cervical ribs are all more or less in line, and none of them are pointed at the big protuberances, which stick way out ventrolaterally.

Here I’ve drawn in the likely trajectories of the longus colli ventralis tendons. My little red pathways don’t precisely match the cervical ribs as mounted, but there’s a lot of distortion and restoration going on. For example, comparing with Gilmore’s plate we can see that the cervical ribs of C5, which point downward compared to all the others, only do that because someone forced them to — the whole anterior portion of the rib, where the shaft would actually join to the capitulum and tuberculum, is reconstructed. Even if I’m a little off, it’s clear that the cervical ribs shafts point backward, they’re all more or less in two parallel lines, and none of them point down and out toward the ventrolateral processes. The photo contains a mountain of useful morphological information that you’d never get from the lateral views.

My takeaways from all this:

  1. If a person has only seen 2D images of a specimen, and especially if those 2D images have only been orthogonal views with no obliques, their little island of knowledge is surrounded by at least a sizeable lake of ignorance, if not a small ocean.
  2. That doesn’t mean that seeing specimens in person is the only antidote — 3D models and 3D prints are extremely useful, and for specimens that are difficult to manipulate because of their size or fragility, they may be more useful than seeing or handling the specimen, at least for some questions.
  3. For Apatosaurus specifically, those ventrolateral processes cry out for explanation. They’re fairly solid knobs of bone that stick way out past the ossified tendons of the ventral-most neck muscles. That’s a super-weird — and super-expensive — place to invest a bunch of bone if you’re not using it for something fairly important, especially in a lineage that had just spent the last 80-100 million years making their necks as light as possible.
  4. Pursuant to that last point, we’re now in — ugh-ouch-shame — our 8th year of BrontoSMASH!!, with still just the one conference presentation to show for it (Taylor et al. 2015). Prolly time we got moving on that again.

References

I was googling around some photos, confirming to myself that turtles don’t have cervical ribs, when I stumbled across this monstrosity (and when I use that word I mean it as a compliment):

Softshell turtle Trionyx spinifera, cervicodorsal transition in ventral view, anterior to right. Copyright © Mike Dodd, used by kind permission. Original at https://www.amanita-photolibrary.co.uk/animals/trionyx_spinifera_1496.htm

The specimen is from the collection amassed by Caroline Ponds, formerly a reader in Zoology at Oxford, who picked up most of her specimens as roadkill in Milton Keynes. She has donated this collection to WildCRU (Wildlife Conservation Research Unit) just outside Oxford, just 90 minutes away from me.

The hot news here is of course the zygapophseal articulation between what I am interpreting as the last cervical and the first dorsal. Let’s take a closer look:

As you can see the prezygapophyses of the first dorsal are cylindrical, wrapping smoothly around from a fairly traditional anterodorsal-facing aspect through anterior, anteroventral, ventral, and even posteroventrally-facing. There is no hint of inclination towards the midline as in sane prezygapophyses.

And, providing perfect mates to those prezygs, the postzygapophyses of the last cervical wrap around producing a negative cylinder that encloses the positive one.

This leaves me with questions. Lots of them. For example:

  1. Did I even identify the vertebrae right, or is that “first dorsal” really the last cervical, based on its not carrying a rib? It looks like it’s trying to bear a rib, but not quite carrying it off. (For now I will assume my identification is correct.)
  2. What is the centrum articulation like here? Sadly, it’s obscured in the photo. My guess would be positive cylinder on the front of the dorsal, and a small contact point on the back of the cervical — but it really is just a guess.
  3. Is this unique to Trionyx spinifera, or do all cryptodiran turtles do this to some extent?
  4. If this condition is common among cryptodires, are there  species that take it to an even greater extreme?
  5. What do pleurodire turtles do here?
  6. Why haven’t I spent more of my like looking at the cervicodorsal transitions of turtles?

Just to wash our mouths out after all the theropod-related unpleasantness yesterday:

What we’re seeing here, in glorious 3D, is the 7th cervical vertebrae of BYU 1252-18531. This is an apatosaurine at the Brigham Young University Museum of Paleontology which the museum has catalogued as “Apatosaurus excelsus” (i.e. Brontosaurus excelsus), and which Tschopp et al. (2015) tentatively referred to Brontosaurus parvus, but which I suspect is most likely good old Apatosaurus louisae.

It’s in the rarely seen ventral view, which really emphasizes the ludicrously over-engineered cervical ribs. Get your 3D glasses on and marvel at how they come lunging out of the screen at you, like giant insects in a 1950s B-movie.

So beautiful.

Last time, I showed you a photo of the head and neck of the London Diplodocus and asked what was wrong. Quite a few of you got it right (including Matt when we were chatting, but I asked him not to give it away by posting a comment). The 100 SV-POW! dollars, with their cash value of $0.00, go to Orribec, who was the first to reply that the atlas (cervical 1) is upside-down.

Here is again, from the other side:

The Natural History Museum’s Carnegie Diplodocus cast, skull and anterior cervical vertebrae in left lateral view. Photograph by Mike Taylor.

I noticed this — when it seems the people putting up the skeleton did not, unless this is a deliberate joke — because I happened to be particularly tuned into atlas ribs at the time. You can see what appears a tiny rib hanging below the atlas, but no neural arch above it projecting up and back to meet the prezygapophyses of the axis (cervical 2). In fact the “cervical rib” on this left side is the neural arch of the right side, rotated 180 degrees about the axis of the neck.

Here’s how this should look, from the Carnegie Museum’s own Diplodocus:

The Carnegie Museum’s Diplodocus mount, skull and anterior cervical vertebrae in left lateral view. Photograph by Matt Lamanna.

In this picture, the atlas seems to be pretty much fused onto the axis, as seen in Gilmore (1936: figure 6) which Matt helpfully reproduced in Tutorial 36.

(Digression 1: you might think that this atlas is the real thing, since the Carnegie’s mount is the one with the real CM 84/94/307 material in it. But no: the atlas does not belong to any of those, which all lack this element. It seems to be a sculpture, but we can’t figure out what it’s based on.)

(Digression 2: you might notice that the London and Carnegie skulls are rather different. That’s because the London cast still has the original skull supplied in 1907, which is a sculpture based on CM 622 (rear) and USNM 2673 (the rest), while the Carnegie’s mount at some point had its skull replaced by a cast of CM 11161 — though no-one knows when.)

(Digression 3: the diplodocine originally catalogued as CM 662, on which the rear of the skull was based, was named as the holotype of a new species Diplodocus hayi by Holland (1924), traded to the Cleveland Museum of Natural History in 1956 where it was numbered CMNH 10670, then traded on the Houston Museum of Natural History in 1963 where istbecame HMNS 175, mounted in  Houston in 1975, remounted between 2013 and 2015, and finally moved to its own new genus Galeamopus by Tschopp et al. 2015. Yes, this stuff gets complicated.)

In fact, it’s amazing how much stuff we actually don’t know about these classic specimens, including the source of the atlas for both the Carnegie mount and the various casts — which are not the same. If only there was a single definitive publication that gathered everything that is known about these mounts. Oh well, maybe some day.

Now everyone knows that all the Carnegie Diplodocus mounts around the world were cast from the same molds, and so they all have the same altas <SCREEEECH> wait what?

The Muséum National d’Histoire Naturelle’s Carnegie Diplodocus cast, posterior part of skull and anterior cervical vertebrae in left lateral view. Photograph by Vincent Reneleau.

Here we are in Paris, and the atlas has these two honking great ribs. I have not seen these in any other Carnegie Diplodocus. I know they’re absent from the Berlin cast (thanks to Daniela Schwarz), from the Vernal re-cast (personal observation) and of course from the London cast. I would welcome observations (or even better, photos) from anyone who’s in a position to look at the Vienna, Bologna, Moscow, La Plata, Madrid or Mexico City casts.

So where did these atlas ribs come from? As with so much of this, no-one really knows. It’s especially mysterious as the Paris mount is supposed to be completely unchanged since its initial mounting. But some clue to the origin of the ribs in this mount is found in Holland (1906:249–250):

Accompanying the elements of the atlas sent to the writer for study by the kindness of Professor Osborn  [i.e. AMNH 969] are two bones, undoubtedly cervical ribs. They are both bones belonging on the right side of the centra. They are reported to have been found at the same place at which the atlas was found. The writer is inclined to think that the larger of these two bones (Fig. 20), was probably the rib of the atlas and indeed it requires but little effort to see that it might very well have served such a function, and that the smaller bone (Fig. 21) was the rib of the axis. Were the stump of the rib which remains attached to the axis in the Carnegie Museum, and which Mr. Hatcher has figured, removed, this smaller rib might take its place and would undoubtedly articulate very neatly to the facet

In case you’re too lazy to go and look at Holland’s illustrations for yourself, here they are.

The atlas rib:

The axis rib:

Holland went on:

In case the view entertained by the writer is correct, the form of the atlas and the axis with their attached ribs would be as given in the accompanying sketch (Fig. 22) rather than as given in the figure which has been published by Mr. Hatcher. Such a location of these parts has in its favor the analogy of the crocodilian skeleton.

Here is that composite atlas/axis complex:

(This arrangement with closely appressed atlas and axis ribs should ring a bell for anyone who’s looked much at croc necks, as for example in Taylor and Wedel 2013:figure 19.)

The atlas ribs on the Paris mount look a decent match for the one illustrated by Holland (1906:figure 20), so it seems a reasonable guess that they were sculpted based on that element. But that only leaves us with two more mysteries:

  1. Why do we see these atlas ribs only on the Paris cast, not in the Carnegie original or any of the other casts (that I know of)?
  2. Why does this cast have atlas ribs based on one of Holland’s elements, but not axis ribs based on the other?

Anyone?

References

 

Last Saturday I was at a wedding at Holy Trinity Brompton, a London church that is conveniently located a ten-minute stroll from the Natural History Museum. As I am currently working on a history paper concerning the Carnegie Diplodocus, I persuaded my wife, my eldest son and his fiancée to join me for a quick scoot around the “Dippy Returns” exhibition.

Here is a photo that I took:

Something is wrong here — and I don’t just mean the NHM exhibition’s stygian lighting.

Who can tell me what it is? $100 in SV-POW! Dollars(*) awaits the first person to get it right in the comments.

 


(*) Cash value: $0.00.

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?

Vertebrae of Haplocanthosaurus (A-C) and a giraffe (D-F) illustrating three ways of orienting a vertebra: articular surfaces vertical — or at least the caudal articular surface vertical (A and D), floor of the neural canal horizontal (B and E), and similarity in articulation (C and F). See the paper for details! Taylor and Wedel (2002: fig. 6).

This is a lovely cosmic alignment: right after the 15th anniversary of this blog, Mike and I have our 11th coauthored publication (not counting abstracts and preprints) out today.

Taylor, Michael P., and Wedel, Mathew J. 2022. What do we mean by the directions “cranial” and “caudal” on a vertebra? Journal of Paleontological Techniques 25:1-24.

This one started back in 2018, with Mike’s post, What does it mean for a vertebra to be “horizontal”? That post and subsequent posts on the same topic (one, two, three) provoked interesting discussions in the comment threads, and convinced us that there was something here worth grappling with. We gave a presentation on the topic at the 1st Palaeontological Virtual Congress that December, which we made available as a preprint, which led to us writing the paper in the open, which led to another preprint (of the paper this time, not the talk).

Orienting vertebrae with the long axis of the centrum held horizontally seems simple enough, but choosing landmarks can be surprisingly complex. Taylor and Wedel (2022 fig. 5).

This project represented some interesting watersheds for us. It was not our first time turning a series of blog posts into a paper — see our 2013 paper on neural spine bifurcation for that — but it was our first time writing a joint paper in the open (Mike had started writing the Archbishop description in the open a few months earlier). It was also the last, or at least the most recent, manuscript that we released as a preprint, although we’ve released some conference presentations as preprints since then. I’m much less interested in preprints than I used to be, for reasons explained in this post, and I think Mike sees them as rather pointless if you’re writing the paper in the open anyway, which is his standard approach these days (Mike, feel free to correct me here or in the comments if I’m mischaracterizing your position).

So, we got it submitted, we got reviews, and then…we sat on them for a while. We have both struggled in the last few years with Getting Things Done, or at least Getting Things Finished (Mike’s account, my own), and this paper suffered from that. Part of the problem is that Mike and have far too many projects going at any one time. At last count, we have about 20 joint projects in various stages of gestation, and about 11 more that we’ve admitted we’re never going to get to (our To Don’t list), and that doesn’t count our collaborations with others (like the dozen or so papers I have planned with Jessie Atterholt). We simply can’t keep so many plates spinning, and we’re both working hard at pruning our project list and saying ‘no’ to new things — or, if we do think of new projects, we try to hand them off to others as quickly and cleanly as possible.

Two different ways of looking at a Haplocanthosaurus tail vertebra. Read on for a couple of recent real-life examples. Taylor and Wedel (2022: fig. 2).

Anyway, Mike got rolling on the revisions a few months ago, and it was accepted for publication sometime in late spring or early summer, I think. Normally it would have been published in days, but the Journal of Paleontological Techniques was moving between websites and servers, and that took a while. But Mike and I were in no tearing rush, and the paper is out today, so all is well.

One of the bits of the paper that I’m most proud of is the description of cheap and easy methods for determining the orientation of the neural canal. For neural canals that are open, either because they were fully prepped or never full of matrix to begin with, there’s the rolled-up-piece-of-paper method, which I believe first appeared on the blog back when I was posting photos of the tail vertebrae of the Brachiosaurus altithorax holotype. For neural canals that aren’t open, Mike came up with the Blu-tack-and-toothpick method, as shown in Figure 12 in the new paper:

A 3d print of NHMUK PV R2095, the holotype of Xenoposeidon, illustrating the toothpick method of determining neural canal orientation. Taylor and Wedel (2022: fig. 12).

I know both methods work because I recently had occasion to use them, studying the Haplocanthosaurus holotypes (see this post). For CM 572, the neural canal of the first caudal vertebra is full of matrix, so I used a variant of the toothpick method. I didn’t actually have Blu-tack or toothpicks, so I cut thin pieces of plastic from the edge of an SVP scale bar and stuck them in bits of kneadable eraser. It worked just fine:

The neural canal of caudal 2 was prepped, so I could use the rolled-up-piece-of-paper method:

(Incidentally, Mike and I refer to our low-tech orientation-visualizers as “neural-canal-inators”, in honor of Dr. Heinz Doofenshmirtz from Phineas and Ferb.)

In the above photos, notice how terribly thin the base of the neural arch is, antero-posteriorly. Both of these vertebrae are in pretty good shape, without much breakage or missing material, and their morphology is broadly consistent with that of other proximal caudals of Haplocanthosaurus, so we can’t write this off as distortion. As weird as it looks, this is just what Haplo proximal caudals were like. And with the neural canals held horizontally, the first two caudals end up oriented like so:

Now, as we pointed out in the paper, the titular question is not about determining the posture of the vertebrae in life, it’s about defining the directions ‘cranial’ and ‘caudal’ for isolated vertebrae — Mike asked the question back when for the holotype (single) dorsal vertebra of Xenoposeidon. But an interesting spin-off for me has been getting confronted with the weirdness of vertebrae whose articular surfaces are nowhere near orthogonal with their neural canals. I tilted those CM 572 Haplo caudals so that their neural canals were horizontal partly because that’s the preferred orientation that Mike and I landed on in the course of this work, but also partly because to me, that’s a more arresting image than the preceding ones with the articular faces held vertically. I’m both freaked out and fascinated, and that seems like a promising combination — there are mysteries here that cry out to be solved.

As usual, we have loads of people to thank. In addition to all those listed in the Acknowledgments of the new paper, I’m grateful to Matt Lamanna and Amy Henrici of the Carnegie Museum of Natural History for letting me play with study the Haplo specimens in their care. Mike and I also owe a huge thanks to the editorial team at the Journal of Paleontological Techniques. We reached out to them a few days ago to ask if it might be possible to get our in-press paper done and out in time for SV-POW!’s anniversary weekend, and they pitched in to make it happen.

What’s next? We weighed the evidence and formulated what the best solution we could think of. Now it’s up to the world to decide if that was a useful contribution. The comment thread is open — let’s find out.

They grow up so fast, don’t they?

Matt and I, with our silent partner Darren, started SV-POW! fifteen years ago to the day, as a sort of jokey riff on NASA’s Astronomy Picture of the Day. Our first post, on 1 October 2007, was a photograph of what we called “the most iconic of sauropod vertebrae, the 8th cervical of the Brachiosaurus brancai type specimen HMN SII”. Now, here in glorious monochrome, is that same vertebra fifteen years on!

(The specimen that it’s from is now recognised as belonging to the separate brachiosaurid genus Giraffatitan, and it’s the paralectotype of the species Giraffatitan brancai.)

Obviously what we’re seeing here is not the real thing — very heavy and very fragile — but a life-sized 3D model, carved out of styrofoam by a CNC machine (computerized carving machine) using surface-scan data of the original specimen. This was done at Research Casting International, and we bring you this photo courtesy of Peter May, Garth Dallman, and the rest of the folks at RCI.

The inside of RCI’s workshop is an interesting place — I’ve never been there myself, but it’s at least Matt’s second visit, and it’s very high on my To Visit list. I especially like the “RAPTOR” box just behind and above Matt’s head.

This photo, unfortunately, makes the vertebra look smaller than it is, because when Matt took the selfie he was holding it further back than his own head. It’s still interesting, though, to see where the balance point is for holding it one-handed. It seems that the rear half of the vertebra is denser than the front half. But of course, that’s only when it’s a solid constant-density volume. The real bone, with all its pneumatic internal structures, might have been quite different.

Needless to say, HMN SII:C8 (or MB.R.2181:C8, as we must now call it) is a very old friend on this blog, to the point where it should probably have a category of its own. Among many other appearances it’s popped up in tutorials 2 (Basic vertebral anatomy), 4 (Laminae) and 21 (How to measure the length of a centrum), as well as Bifid Brachiosaurs, Batman! (6 September 2009), What a 23% longer torso looks like (20 September 2009), Plateosaurus is pathetic and its doppelganger Plateosaurus is comical (16 January and 5 September 2013), and of course Copyright: promoting the Progress of Science and useful Arts by preventing access to 105-year-old quarry maps (11 October 2015).

If you want to see more exciting photos of this glorious vertebra — and indeed of many other sauropod vertebrae — stay tuned for the next fifteen years!

 
 
 
Mastodon

I made this for my own amusement, and thought you guys may as well get to benefit from it, too.

Melstrom et al. (2016:figure 4). Pectoral vertebrae of a juvenile specimen of Barosaurus sp. (DINO 2921) from the Upper Jurassic Morrison Formation of Utah, U.S.A., in right lateral view (red-cyan anaglyph made from stereopair).

Enjoy!

References

  • Melstrom, Keegan M., Michael D. D’Emic, Daniel Chure and Jeffrey A. Wilson. 2016. A juvenile sauropod dinosaur from the Late Jurassic of Utah, U.S.A., presents further evidence of an avian style air-sac system. Journal of Vertebrate Paleontology 36(4):e1111898. doi:10.1080/02724634.2016.1111898

 

For reasons that would be otiose, at this moment, to rehearse, I recently found myself in need of a hemisected turkey cervical. Happily, I own five skeletonised turkey necks, so it was with me the work of a moment to select a candidate. But now what? How to hemisect it? We have  discussed plenty of hemisected things here at SV-POW!, but they tend to have been produced using heavy machinery such as a band saw: something that I singularly lack.

SPOILER: I found a way. Here is a domestic turkey Meleagris gallopavo domesticus, 9th cervical vertebra, hemisected, in right medial view. Read on to discover the extremely high-tech approach that yielded this prize. It’s propped up on some kind of turkey bone to help me get a good medial perspective, I am thinking maybe the pygostyle?

One idea was to use an angle-grinder: not to cut down the midline of the vertebra — it would be much too blunt and powerful for a small, delicate vertebra — but to use as a sanding surface, locking the grinder in place and holding the vertebra up against the spinning plate. That might work well, assuming I could find a way to secure the angle grinder safely, but as it happened my need for a hemisected vertebra came up during a power cut. (Thanks, Storm Eunice!)

So I did it the way the Amish do their vertebral hemisections: by hand, simply by rubbing the vertebra against a sheet of sandpaper:

CT scanning: the Amish method.

This is not as laborious as you might think. I used a single sheet of medium-grade sandpaper, and it took maybe 15–20 minutes. And I just rubbed back and forth while exerting downward pressure. Initially I worked my way only through the prezygapophyseal ramus, which is the part of the turkey cervical that extends the furthest laterally. Once I was satisfied that the plane between eroded prezyg and the intact postzyg was parasagittal, I just kept the vertebra parallel to the sandpaper and kept rubbing. (Sorry I didn’t think to get a photo at this stage.)

One thing that took me by surprise is that there was so very much bone dust. I mean, I am an idiot that this surprised me, since the whole purpose of this exercise was to reduce one half of this vertebra to bone dust. But the lesson to be learned here is to do it on the easily-cleaned bathroom floor — not on the desk next to the computer keyboard and above a carpet. Learn from my mistakes, folks!

Anyway, after some work on the prezyg/postzyg pair, here’s how the vertebra was looking:

You can see straight away that the prezyg ramus, postzyg ramus and parapophyseal ramus are extensively pneumatized, honeycombed with small, irregular air-spaces. In this image it looks like the region of bone between the pre- and postzygs is much more solid, but this is an illusion: what we’re seeing here is a section through the cortical  bone of the neural arch, cut parallel to the surface. Let this be a warning not to over-interpret individual slices of CT-scans!

Once we get a little deeper, we see that the whole wall of the neural arch — and indeed the centrum and the neural spine — is honeycombed, just like the zyg rami:

Now we have another area of what I’m going to call Phantom Apneumaticity: the posterior part of the centrum looks like solid bone, apart from a few pneumatic spaces in the posteroventral extremity. Again, this is an illusion.

Here’s the next place I stopped:

Here, the Phantom Apneumaticity is even more striking: seeing just this as a CT slice could easily mislead someone into thinking that almost the whole of the posteroventral part of the centrum is solid bone. But again, it’s just that we’re very close to the surface of the bone, and seeing a slice parallel to that surface.

This last image also shows an important point of technique: there is a low convex ridge running across the phantom apneumatic area from the top of the cotyle to the base of the centrum. This is where I had changed the angle I was holding the vertebra at, so I accidentally sanded the posteroventral part of the vertebra more than the rest. I found that it was important during this process to keep checking the angles, and to adjust: making sure I wasn’t sanding more from the front than the back, or from the top than the bottom, or leaving a ridge like this.

Also in this last photo you can see that I was just beginning to break through into the neural canal: the anterior part of it is now exposed, between the anterior part of the neural spine and the anterior articular surface. At this stage I sighted along from in front to get a sense of how much further I had to go:

Domestic turkey Meleagris gallopavo domesticus, 9th cervical vertebra, most of right side removed, in anterior view with dorsal to the right. Propped up on the coracoid of a different, larger, turkey.

Quite a way, I guess. Here it is rotated and cropped, so you can more easily recognise it:

Domestic turkey Meleagris gallopavo domesticus, 9th cervical vertebra, most of right side removed, in anterior view. You can see that the neural canal is still mostly intact.

More sanding was required. I sanded some more.

You’ve already seen the final result up at the top of the page, but here is a cleaned-up version of that image, oriented according to Definition 3 of Taylor and Wedel (2019):

Domestic turkey Meleagris gallopavo domesticus, 9th cervical vertebra, hemisected, in right medial view.

And if that isn’t beautiful, what is?

The exciting thing is, anyone can make one of these. Matt’s already explained how to extract and clean up bird vertebrae and given you some ideas of what to do with them. Prepare out some turkey vertebrae and get going with the sandpaper!

I leave you with one more image: the hemisected vertebra in anterior view, oriented with dorsal to the top, and mirrored so it make up a complete vertebra once more. Enjoy!

References