I planned to post this last spring but I never got around to it. I think I have a mental block about discussing the glycogen body. Partly because I’ve been burned by it before, partly because no-one knows what it does and that’s unsatsifying, partly because I didn’t want to plow through all the new literature on it (despite which, the function remains unknown).

Then I decided, screw it, I’ll let the slides speak for themselves, and the actual text of the post can just be navel-gazing and whingeing. Which you are “enjoying” right now.

So, there’s the glycogen body. It balloons out between the dorsal halves of the spinal cord, it’s made of glial cells (neuron support cells) that are packed with glycogen, and nobody knows why it’s there. On the graph of easy-to-find and frustrating-to-study it is really pushing the envelope.

Update: the role of the glycogen body in the ‘second brain’ myth is covered in the next post.

Previous entries in the “Bird neural canals are weird” series:

Here are some stubbornly-not-updated references for the images I used in the slides:

  • Huber, J.F. 1936. Nerve roots and nuclear groups in the spinal cord of the pigeon. Journal of Comparative Neurology 65(1): 43-91.
  • Streeter, G.L. 1904. The structure of the spinal cord of the ostrich. American Journal of Anatomy 3(1):1-27.
  • Watterson, R.L. 1949. Development of the glycogen body of the chick spinal cord. I. Normal morphogenesis, vasculogenesis and anatomical relationships. Journal of Morphology 85(2): 337-389.
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Ray Wilhite posted this gorgeous image on a Facebook thread, and we’re re-posting it here with his permission.

It’s taken from a poster that Ray co-authored (Roberts et al. 2016). We’re looking here at a coronal cross-section of a hen (age not specified), with anterior to the left. Latex has been injected into the air sacs and lungs, highlighting them in shocking pink.

FInding your way around: the big yellow blobs near the middle are vitelline follicles. Just to their left, the two rounded red triangles that look like networks are the lungs. All the rest of the pink is diverticula and air-sacs: the interclavicle air-sac to the left, the caudal thoracic air-sac right behind the left (lower) lung, and abdominal air-sacs running backwards from the tips of the lungs. The big white oval is a calcified egg.

More from this poster in a subsequent post!

References

  • Roberts, John, Ray Wilhite, Gregory Almond, Wallace D Berry, Tami Kelly, Terry Slaten, Laurie McCall and Drury R. Reavill. 2016. Gross and histologic diagnosis of retrograde yolk inhalation in poultry. The American Association of Avian Pathologists, San Antonio, Texas. doi:10.13140/RG.2.2.28204.26246

 

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

2018 at SV-POW!

December 31, 2018

Last year about this time I vowed to return SV-POW! to its nominal roots: a new post at least once a week for all of 2018. It had been a while since the blog had lived up to the letter of its name, and I thought it would be a fun challenge to see if blogging to a schedule again would be inspiring or oppressive.

Then I went and had probably the busiest year of my professional career: 12 invited talks in 5 different states, 12 visits to museum collections or research labs, plus another 3 visits to museum public galleries for fun, 4 trips for fieldwork, 3 conference presentations, and more CT scanning than I have done since the last millennium. Happily, I am not the sole proprietor here and Mike and I can take turns driving when the other is occupied.

So how’d we do?

In January I blogged about weird neural canals, part of an obsession that would occupy most of my mental bandwidth this year, and also about the impact of Don Glut’s New Dinosaur Dictionary when I was a kid. A post on sauropod gigantism sparked a very active discussion that ran to 47 comments, which is a rarity these days.

Gonzalez Riga et al. (2018: figure 6). Mendozasaurus neguyelap cervical vertebra (IANIGLA-PV 076/1) in (A) anterior, (B) left lateral, (C) posterior, (D) right lateral, (E) ventral and (F) dorsal views. Scale bar = 150 mm. Sorry it’s monochrome, but that’s how it appears in the paper.

February was mostly run-of-the-mill posts on vertebral morphology and open access. The standouts were Mike’s post on weird cervical vertebrae and my unexpectedly popular off-topic post on the durability of tungsten. I see that my teaser post on a trip to see elephant seals has not yet been followed up. There’s a lot of that around here–we’re often too busy with the next thing to finish up the last thing. I’ve given up feeling bad about that, and accepted that it’s just how we roll.

Mike ruled March with a flurry of posts, including a couple worth revisiting on how grant funding is awarded and on the state of play vis-a-vis Big Publishing. Also (and uncharacteristically) Mike posted on appendicular bones of birds, both skinny and fat. It was left to me to represent for sauropods, with posts on the cervical vertebrae of Alamosaurus and Suuwassea and some noodling about sauropod skin.

I flew solo in April, with some posts derived from my spring travels. A very long post on the suitability of dinosaur femora as clubs was good, goofy fun, but an arresting video of a rhino going ass-over-teakettle and getting up unhurt, and the humility that should inspire in us, is the clear standout for the month.

In May I started CT scanning sauropod vertebrae again and went to Utah for the first of several stints of fieldwork this year. Mike started work on the Archbishop (allegedly), and blogged about Argentinosaurus poop. My series on bird neural canals, represented by these posts (two links) is still incomplete, and has now been superseded by the Haplocanthosaurus presentation at the 1st Palaeontological Virtual Congress.

June was comparative anatomy month here at SV-POW!, with Mike posting on the dead things in his woodshed, and me writing about exploded turtles and the amazing collection of anatomical preparations in Peter Dodson’s office. I also managed two posts about field adventures in the Oklahoma panhandle.

Figure 4. Centra and neural arches of posterior dorsal vertebrae from two rebbachisaurid sauropods (not to scale), highlighting the distinctive “M” shape formed by laminae on the lateral face of the neural arch. A. NHMUK PV R2095, the holotype and only vertebra of Xenoposeidon proneneukos. B. MNHN MRS 1958, a posterior dorsal vertebra from the holotype specimen of Rebbachisaurus garasbae.

In July Mike and I returned to our regular dance partners. For Mike, that meant serious and whimsical posts about Xenoposeidon, which for a few months held the title of the oldest known rebbachisaur. I had Haplocanthosaurus caudals on the brain, both old and new. Posts on fieldwork in Oklahoma and Utah bookended the month.

My fascination with Haplocanthosaurus extended into August, and I CT scanned a Diplodocus caudal and attended a pterosaur conference. Mike kicked off a discussion about vertebral orientation with a pair of posts that would eventually lead to our presentation on the topic at the 1st Palaeo Virtual Congress. And I see that I still owe the world a “down in flames” perspective on my own career.

In September the vertebral orientation discussion expanded to take in the Brachiosaurus holotype and Komodo dragons, and Mike blogged about imposter syndrome. The most personally satisfying event in September was that Jessie Atterholt and I started to get the word out about some of the collaborative research we’ve been doing in the past year, with her very well-received talk at SVPCA and the archiving of our abstract and slideshow on PeerJ Preprints.

October saw the return of #MikeTaylorAwesomeDinoArt, and the 2018 TetZooCon, and #MikeTaylorAwesomeDinoArt at TetZooCon. I also had a return to form, with a series of posts about pneumaticity, and a batch of new paleo-memes. The biggest actual news was the enigmatic Amphicoelias fragillimus dethroning Xenoposeidon as the new world’s oldest rebbachisaur.

November was entirely representative of SV-POW!, with an eclectic grab-bag of posts on a museum mount, neck flexibility, a historical illustration, bird vertebrae, academic publishing, and what is probably our real favorite dinosaur (no matter what we might say when asked in interviews or in person): the insanely overbuilt Apatosaurus.

This month we’re closing out the year with posts on dissecting a pig head, our presentations at the 1st Palaeo Virtual Congress, the open birth of the vertebral orientation paper, a long overdue post on cleaning bird vertebrae, and this, our first yearly retrospective.

The Salutary Effects of Blogging

This blog started as a joke, and we thought we’d see if we could keep up the gag for a whole year. But it very rapidly evolved into something much more serious, in a way that none of us expected. SV-POW! doesn’t just give us a forum to interact with you, our colleagues. It also forces us to talk to each other, regularly, about subjects that we care about. I love reading Mike’s posts, because after all this time, I still often have no idea what he’s going to say. After 18 years of friendship, 14 joint conference presentations, 11 years of blogging together, and 7 coauthored papers, we still regularly surprise each other with unexpected observations and provocative questions. Not only do we not always agree, we very often disagree, but we disagree constructively. Neither of us is willing to let a subject drop until we’ve gotten to the root of the disagreement, and that process sharpens us both.

Bottom line, we both need SV-POW! Not only as a forum for discussion, although that’s rewarding, or as a soapbox, although that’s sometimes useful, or a generator of occasionally publishable ideas, although that’s an unexpected bonus. We need to blog here because it forces us to keep learning what we think and what we know, both individually and as a team. If you enjoy the output or find it interesting or infuriating or worth thinking about, we’re happy — honored, in fact. But at this point I think we would keep blogging if there was no audience at all. It is a whetstone for our minds.

Let’s see what 2019 will bring. Happy New Year, everyone! We’ll see you in the future.

A simply mind-blowing preparation of the skull of an American paddlefish, Polyodon spathula. In life the paddle-shaped snout is covered by thousands of electroreceptors that detect the swarms of zooplankton on which the paddlefish feeds.

This was on display in the gift shop at the Museum of Osteology in Oklahoma City when I visited in July of this year. I was relieved it wasn’t for sale, first because it truly would have bankrupted me, and second because as a fellow excavator of antiquities once said, “It belongs in a museum!”

When I started working on sauropods, I thought their vertebrae were cool but they were loaded with weird structures that I didn’t understand. Then I dissected my first ostrich neck and suddenly everything made sense: this was a muscle attachment, that was a pneumatic feature, this other thing was a ligament scar. Everyone who is interested enough to read this blog should give themselves the same “Aha!” moment. You don’t even have to eat the birds yourselves, lots of people don’t like bird necks and will give them away if you ask.

If you get a whole bird, the neck is usually included with the giblets. Around Thanksgiving and Christmas you can often find bundles of spare turkey necks at your grocer or butcher.

This spring I picked up some smoked turkey necks at the grocery store. I wanted to make turkey stew and I figured I might as well get some toys in the bargain. Here are some neck segments in the crock pot.

And here they are after a few hours of cooking. Time to separate the meat from the bones. That neck segment in the middle of the above photo is a pretty good match for the ostrich neck cross-section in this post.

Here are parts of three vertebrae with the long, multi-segment muscles removed, but with the shorter single-segment muscles still connecting them. Anterior is to the right; that’s a cervical ribs sticking out at the lower right “corner”.

Here’s a single intact cervical in left lateral view with most of the meat off, but ready for a long simmer to loosen the remaining crud. This is roughly the same orientation as the lateral view of Mike’s famous turkey cervical.

Meat goes back in the pot.

Bones go on to the next stage: simmering. One of the nice things about the stepwise process of cleaning bones is that you can stop at any point, put the bones in the freezer, and come back days or months later. This bowl of bones went into the freezer in exactly the state you see here, and I didn’t pull them out and finish cleaning them until last week.

If you have a pot-sized strainer, it makes things easier, especially for rinsing. These aren’t turkey vertebrae, these are the verts from my Thanksgiving ducks. But the principle and the process are the same.

After simmering for an hour or two, it’s time to pick off the loosened muscles, ligaments, cartilage, and so on. Here are two similar turkey cervicals after simmering, in dorsal view with anterior to the right. The one on the left has not been cleaned and has all kinds of crud stuck to it, including a big chunk of intervertebral ligament sticking out between the rami of the postzygapophyses. The one on the right has been through a first-pass cleaning.

What tools should you use? Whatever you have to hand. I like old toothbrushes for scrubbing off little bits of muscle and tendon, toothpicks for shoving spinal cord bits through the neural canal and for picking bits of meat out of hard-to-reach places, and the Mark 1 thumbnail for planing off articular cartilage, as shown here with the back end of a duck cervical.

Here’s the outcome of a cleaning session: on the left, the bowl I used for cleaning the vertebrae. In the top middle, the pile of gloop I pulled off. And on the right, a bowl of cleaned turkey and duck vertebrae, ready for degreasing.

Here are the vertebrae of a couple of ducks after soaking overnight in 3% hydrogen peroxide, the ordinary stuff you get at the drugstore or dollar store.

Here’s another bowl with turkey vertebrae. They were all at the bottom of the bowl when I went to bed, floating when I got up the next morning. This is pretty common with lightweight pneumatic vertebrae: the oxygen bubbling out of the hydrogen peroxide has gotten trapped in the internal air spaces and made the vertebrae buoyant.

After a night in the hydrogen peroxide, it’s time to rinse and dry the vertebrae. I put this mixed lot of turkey and duck verts on a plate with a paper towel and left them out on the kitchen counter. In the summertime, when it’s hot and dry, I might put them outside for a bit and they’d be dry in a couple of hours. Indoors in the winter it can take a couple of days for the vertebrae to get completely dry.

Here’s the same batch of vertebrae a couple of days later, clean and dry and ready for whatever comes next.

Which bird should you use? Bigger birds have vertebrae that are easier to clean, harder to damage, and more fun to look at, but use whatever you can get your hands on. This photo shows the axis, a middle cervical, and a posterior cervical from the turkey (top) and duck (bottom). Note that the duck was so young that the cervical ribs hadn’t fused and they fell off during the cleaning process.

If you’ve been following along, you have some nice clean bird vertebrae to play with. So what now — what should you do with them? That will the subject of an upcoming post. Stay tuned!

In a move that will surprise no-one who’s been paying attention, my and Matt’s presentation of vertebral orientation at the 1st Palaeo Virtual Congress is now up as a PeerJ preprint. Sadly, with the end of the conference period on 15th December, the page for my talk has been deleted, along with some interesting comments. But here at SV-POW!, we have no truck with ephemerality, hence this more permanent manifestation of our work.

Matt’s preprint consists of the abstract, and has the slide deck as a supplementary data file. That’s what he submitted to the conference, with attendees invited to page through it. By contrast, I recorded a video of my talk. I am trying to get that attached to my preprint, but as things stand it’s not there because it’s too big (at 65 Mb).

Meanwhile — and indeed in perpetuity — you can just watch it on YouTube, where I also uploaded it. In the end, that may be a more practical way of making video available anyway, but I do want the preservational benefit of lodging it with a preprint.

Remember, we’re working on the paper in the open. We’d love to get input from you all, and especially from anyone who’s run into this problem before with other taxa. Please, if you have fifteen minutes spare, watch the talk and leave any comments you have: here, on the preprint, on the YouTube page, or as issues in the GitHub tracker!

Reference