Things to Make and Do, Part 25b: what to do with your bird vertebrae

January 7, 2019

If you followed along with the last post in this series, you now have some bird vertebrae to play with. Here are some things to do with them.

1. Learn the parts of the vertebrae, and compare them with those of other animals

Why are we so excited about bird vertebrae around here? Mostly because birds are reasonably long-necked living dinosaurs, and although their vertebrae differ from those of sauropods in relative proportions, all of the same bits are present in roughly the same places. If you know the parts of a bird vertebra and what each one does, you have a solid foundation for inferring the functions of sauropod vertebrae. Here’s a diagram I made for my SVP poster with Kent Sanders way back in 1999. I used an ostrich vertebra here but you should be able to find the same features in a cervical vertebra of just about any bird.

These are both middle cervical vertebrae in right lateral view. A middle cervical vertebra of a big ostrich will be between 3 and 4 inches long (7.5-10 cm), and one from a big brachiosaur like Giraffatitan will be about ten times longer.

I should do a whole post on neck muscles, but for now see this post and this paper.

2. Put the vertebrae in order, and rearticulate them

It is often useful to know where you are in the neck, and the only way to figure that out is to determine the serial position of the vertebrae. Here’s an articulated cervical series of a turkey in left lateral view, from Harvey et al. (1968: pl. 65):

Harvey’s “dorsal spine” is the neural spine or spinous process, and his “ventral spine” is the carotid process. The “alar process” is a sort of bridge of bone connecting the pre- and postzygapophyses; you can see a complete version in C3 in the photo below, and a partial version in C4.

Speaking of that photo, here’s my best attempt at rearticulating the vertebrae from the smoked turkey neck I showed in the previous post, with all of the vertebrae in left dorsolateral view.

These things don’t come with labels and it can take a bit of trial and error to get them all correctly in line. C2 is easy, with its odd articular surface for the atlas and narrow centrum with a ventral keel. Past that, C3 and C4 are usually pretty blocky, the mid-cervicals are long and lean, and then the posterior cervicals really bulk out. Because this neck section had been cut before I got it, some of the vertebrae look a little weird. Somehow I’m missing the front half of C6. The back half of C14 is also gone, presumably still stuck to the bird it went with, and C7 and C12 are both sectioned (this will come in handy later). I’m not 100% certain that I have C9 and C10 in the right order. One handy rule: although the length and neural spine height change in different ways along the column, the vertebrae almost always get wider monotonically from front to back.

And here’s the duck cervical series, in right lateral view. You can see that although the specific form of each vertebra is different from the equivalent vert in a turkey, the same general rules apply regarding change along the column.

Pro tip: I said above that these things don’t come with labels, but you can fix that. Once you have the vertebrae in a satisfactory order, paint a little dot of white-out or gesso on each one, and use a fine-point Sharpie or art pen to write the serial position (bone is porous and the white foundation will keep the ink from possibly making a mess). You may also want to put the vertebrae on a string or a wire to keep them in the correct order, but even so, it’s useful to have the serial position written on each vertebra in case you need to unstring them later.

3. Look at the air spaces

One nice thing about birds is that all of the species that are readily commercially available have pneumatic traces on and in their vertebrae, which are broadly comparable to the pneumatic vertebrae of sauropods.

The dorsal vertebrae of birds are even more obviously similar to those of sauropods than are the cervicals. These dorsal vertebrae of a duck (in left lateral view) show a nice variety of pneumatic features: lateral fossae on the centrum (what in sauropods used to be called “pleurocoels”), both with and without foramina, and complexes of fossae and foramina on the neural arches. Several of the vertebrae have small foramina on the centra that I assume are neurovascular. One of the challenges in working with the skeletal material of small birds is that it becomes very difficult to distinguish small pneumatic foramina and spaces from vascular traces. Although these duck vertebrae have small foramina inside some of the lateral fossae, the centra are mostly filled with trabecular, marrow-filled bone. In this, they are pretty similar to the dorsal vertebrae of Haplocanthosaurus, which have fossae on the neural arches and the upper parts of the centra, but for which the ventral half of each centrum is a brick of non-pneumatic bone. For more on distinguishing pneumatic and vascular traces in vertebrae, see O’Connor (2006) and Wedel (2007).

This turkey cervical, in left posterolateral view, shows some pneumatic features to nice advantage. The lateral pneumatic foramina in bird cervicals are often tucked up inside the cervical rib loops where they can be hard to see and even harder to photograph, but this one is out in the open. Also, the cervicals of this particular turkey have a lot of foramina inside the neural canal. In life these foramina are associated with the supramedullary diverticula, a set of air-filled tubes that occupy part of the neural canal in many birds — see Atterholt and Wedel (2018) for more on this unusual anatomical system. The development of foramina inside the neural canal seems to be pretty variable among individuals. In ostriches I’ve seen individuals in which almost every cervical has foramina inside the canal, and many others with no foramina. For turkeys it’s even more lopsided in my experience; this is the first turkey in which I’ve found really clear pneumatic foramina inside the neural canals. This illustrates one of the most important aspects of pneumaticity: pneumatic foramina and cavities in bones show that air-filled diverticula were present, but the absence of those holes and spaces does not mean that diverticula were absent. Mike and I coined the term “cryptic diverticula” for those that leave no diagnostic traces on the skeleton — for more on that, see the discussion section in Wedel and Taylor (2013b).

Finally, it’s worth taking a look at the air spaces inside the vertebrae. Here’s a view into C12 of the turkey cervical series shown above. The saw cut that sectioned this neck happened to go through the front end of this vertebra, and with a little clean-up the honeycomb of internal spaces is beautifully displayed. If you are working with an intact vertebra, the easiest way to see this for yourself is to get some sandpaper and sand off the front end of the vertebra. It only takes a few minutes and you’ll be less likely to damage the vertebrae or your fingers than if you cut the vertebra with a saw. Similar complexes of small pneumatic cavities are present in the vertebrae of some derived diplodocoids, like Barosaurus (see the lateral view in the middle of this figure), and in most titanosauriforms (for example).

I have one more thing for you to look for in your bird vertebrae, and that will be the subject of the next installment in this series. Stay tuned!

References

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7 Responses to “Things to Make and Do, Part 25b: what to do with your bird vertebrae”

  1. Zachary Miller Says:

    I am, as usual, insanely jealous of your tungsten cube. I hope to have one someday.

    I have a couple serial chicken vertebrae in beautiful condition that I found on a beach in Kauai several years ago (some leg bones too). I really need to hit up a local meat market to pull in a turkey neck (and maybe the rest of the turkey too). Back in college, one of our biology projects was to mount a bird skeleton. I was able to procure a wigeon (if memory serves) but I hardly “mounted” it. However, I very much enjoyed the experience and would like to do it for real this time with the proper materials and a much larger bird that would withstand repeated rounds of boiling.

  2. Matt Wedel Says:

    The trick to simmering bird bones is more time and less heat. A rapid boil is usually a bad idea. I’ve seen people online have amazing results with a pressure cooker but I’ve never tried it myself.

    Cleaning and rearticulating bird bones is great fun. I was at the store last night and found a turkey neck for $0.44. It’s in my freezer right now, hopefully awaiting hemisection by band saw. If that happens, you’ll see it here first.

    I should have mentioned in the post that the scale cube here is half an inch on a side. As I mentioned in my tungsten cube post, it is okay but not nearly the punch in the brainpan that you get a from a 1.5″ or larger cube.

    And now that you’ve reminded me of it, time to retrieve my big tungsten cube from the other side of the desk and play with it.

  3. Mike Taylor Says:

    This is a beautiful post. Every single person who is seriously interested in dinosaurs, or indeed in anything, should read it and go through the processes you describe. Thanks for writing it.

  4. Matt Wedel Says:

    You’re welcome — and thanks for the kind words. In retrospect, I cannot believe that it took more than a decade for me to write this post, which mostly could have been done the same month we launched the blog.

    I think you will like the next post as well.

  5. Brad Lichtenstein Says:

    Ok, looks like I forgot to ask: the fascinating one to me is the hemisected bone showing “pneumaticity”. I get that fossils are somewhat harder to come by, and that air spaces may fill with a lower-contrast mineral than what mineralizes the bones, but has anyone bothered to do this with fossil specimens? I mean, there’s a lot of T. rex and Allosaurus specimens, and presumably as many or more of their larger prey. Surely one of each is sufficiently incomplete and “usual” enough to go sawing thru them? Yes, non-invasive imaging is probably better, but I’m told the minerals involved don’t always allow that….?

  6. Brad Lichtenstein Says:

    Aaand for those of us who are interested and quite happy that an expert is going through the trouble, is it ok to not cook the skeleton ourselves? I guess if we’re already eating & cooking the whole bird, it could be …an interesting lesson with the kiddos… but isn’t there some way to preserve the order the verts come in? Given how my wife raves about her instant pot (she makes great food in a small fraction of the time she used to take), it might make sense that it would work a LOT faster and let you even steam everything in situ.

  7. Matt Wedel Says:

    Hi Brad, I’ll attempt to answer your questions in the order they came in.

    Can you see pneumaticity in fossil specimens by cutting and polishing them? Yes! Before the advent of CT this was sometimes done even with nice specimens, and it’s still done with incomplete ones to make display and education pieces. We’ve shown cut and polished vert sections a few times, notably here, here, and here.

    If you don’t want to cook a skeleton yourself, I can’t force you. But it seems silly to deprive yourself of such a cool experience.

    Preserving the order the verts come in: I suppose you could just be very careful and maybe cook them in separate containers or one at a time, but it seems a lot simpler to just figure out the order when you’re done. I find that much less hassle than trying to keep the verts in line while cooking and cleaning them. It’s no good trying to put them on a string before they’re clean, because the neural canals are filled with gross, swelled-up cooked spinal cord.

    On the instant pot, it would probably work quite well. I’ve never tried it, but I’ve seen people online get great results prepping bones with a pressure cooker.

    Anyway, my strong recommendation is to prep yourself some bird vertebrae. I suspect that if you do, you’ll be surprised at how cool they are.


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