We were probably wrong about caudal pneumaticity in Ca13 of the Brontosaurus excelsus holotype YPM 1980

March 20, 2023

This is one of those posts where the title pretty much says it all, but here’s the detailed version.

Recap: the 2013 paper

In Matt’s and my 2013 paper Caudal pneumaticity and pneumatic hiatuses in the sauropod dinosaurs Giraffatitan and Apatosaurus (Wedel and Taylor 2013b), we wrote about the Brontosaurus excelsus holotype 1980:

Much more convincing, however, are two isolated lateral fossae: one on the left side of caudal 9, the other on the right side of caudal 13 (Figure 10). Both of these are much larger than the aforementioned foramina – about 6 cm across – and have distinct lips. There is absolutely no trace of similar fossae in any of the other caudals, so these fossae represent a bilateral pneumatic hiatus of at least seven vertebrae

And we illustrated the right side of Ca13 in our figure 10:

Wedel and Taylor (2013:figure 10). An isolated pneumatic fossa is present on the right side of caudal vertebra 13 in Apatosaurus excelsus holotype YPM 1980. The front of the vertebra and the fossa are reconstructed, but enough of the original fossil is visible to show that the feature is genuine.

Fast forward to 2023

The Yale Brontosaurus has been dismounted and sent to RCI in Canada for some long overdue TLC. It’s being re-prepared, and Brian Curtice has seen the material close up. The news from Brian is not good: I quote some of his emails. First, on 26 January:

The 1980 caudal 13 it isn’t pneumatic. That whole hole is plaster. The 2 verts in front of it have similar damage but on the opposite side. It looks like they were damaged during preservation, excavation, or preparation.

Then on 27 January:

Quick caudal pneumatic update: other than the fact 1980 has a large number of what I dub nutrient foramina there isn’t any shiny surfaces, no odd sculpting, fluting, etc. the bone is exquisite in these areas but will soon be painted black.

Later that day:

It was also exceptionally difficult to sometimes tell what was actual bone. Barbour [1890 — ed.] is spot on at what Marsh had done. The preparators sometimes couldn’t be sure without acetone and an air scribe… I did the best I could but my goodness it was tough and may have errors. Thus I stayed towards what I was positive on.

On 3 February, I wrote back to Brian asking:

My question about the “pneumatic fossa” in caudal 13 is: why did they sculpt it like that? It would have been the simplest thing in the world to give it a simple flat lateral aspect, like the other caudals, so what made them put the fossa in? One possible answer is that that’s what the bone was actually like, but smashed up, and they “repaired” it. I guess we are unlikely ever to know.

He replied the same day:

There are 3 caudals (11-13, pics attached) with similarly damaged bone, punky and smashed and “beat up”, with 11 and 12 having the damage on the left and ventral and 13 on the right. I suspect they were lying close to one another. I couldn’t tell if it was trampling, but it didn’t seem like it was from being hacked from the ground.
[…]
As to why they did it? I suspect because 13’s damage wasn’t as jagged, they could plaster over it easier? We’ll never know for sure.

Brian sent a photo of the re-prepared caudal 13, showing … well, see for yourself:

Truthfully, I don’t find this especially compelling. But that’s about the inadequacy of photos for this kind of work. My inclination is to trust Brian’s interpretation, while wondering how Matt and I were both fooled back in June 2012 when we visited YPM together and spent significant time gazing at this caudal.

So what now?

The good news for us is that this doesn’t really change any of our arguments or conclusion in the 2013 paper. We said that there is previously undocumented evidence of caudal pneumaticity in apatosaurines[1] — and there still is, in the other specimen we figured, FMNH P25112, in our figure 9. And the significant conclusion of the papers was the intermittent and unpredictable pneumatization along the tails of sauropods is compelling evidence for extensive “cryptic pneumaticity” — that is, for soft-tissue pneumatization alongside vertebrae that did not penetrate the bone. That conclusion is still good.

But still: one of the data-points we relied on in making that argument no longer looks solid, and it feels like the honest thing is to document that. It probably doesn’t warrant a follow-up paper or even an erratum. But it does warrant a blog-post, and this is it.

Thanks to Brian for bringing it to our attention!

Notes

[1]. In the paper we said “in Apatosaurus“, not “in apatosaurines”. But that was back when Apatosaurus was the only recognized apatosaurine, so it amounted t0 the same thing. If we were writing it in the post-Tschopp-et-al. world of today, we’d say “in apatosaurines”.

References

 

Posted by Mike Taylor
Filed in Brontosaurus, caudal, pneumaticity, Yale Peabody Museum
2 Comments »

An arresting image of an apatosaur vertebra

March 3, 2023

Here’s a cool photo of an apatosaur cervical in anterior view. This is from R. McNeill Alexander’s wonderful book Bones: The Unity of Form and Function, which was published in 1994. The whole book is packed with gorgeous full-color photos like this, and you can still get new copies for cover price (f’rinstance).

I remember stumbling across this image not long after I started working on sauropod vertebrae back in the late 90s, and being completely taken aback by the size of the cervical ribs. Up to that point I’d mostly been grokking the long, graceful cervicals of brachiosaurs, and the ridiculously overbuilt apatosaurine cervical morphology was a real kick in the brainpan. That’s well-trod ground here at SV-POW!, but this is still a beautiful photo. I suspect that the vertebra has been at least somewhat restored — some of the texturing on the condyle and under the diapophyses looks suspiciously like it was applied with tools or maybe just human fingers — but in general this is a pretty faithful representation of what an apatosaur cervical looks like from the front.

One thing that always strikes me about views like this is that you could take the centrum of this vertebra, strip off the neural arch and all the apophyses, and stick it through either one of the cervical ribs loops without scraping the sides. If life, the cervical rib loops held the (comparatively small) vertebral arteries and the (comparatively gigantic) intertransverse diverticula. We know this because that’s how birds are built, and because different apatosaurine specimens show pneumatic traces almost all the way around the inside of the cervical rib loop. The same is true in theropods like Majungasaurus, as Pat O’Connor showed in a lovely figure in his 2006 paper (O’Connor 2006: fig. 16). The volume of air in each of the paired cervical rib loops would have simply dwarfed the volume of air inside or even alongside the centrum. I wanted to visualize that better so I took my trusty old CT cross-section of OMNH 1094 and pasted it on top of this vert, stretching it a bit in GIMP to improve the fit:

Another thing that this photo shows nicely are the pneumatic fossae on the anterior surfaces of the cervical ribs. I’ve seen those features on loads of apatosaur cervical ribs, but I’ve never seen them discussed anywhere. I have thoughts on why those fossae are there, but that story will have to keep for another time.

References

 

Posted by Matt Wedel
Filed in Apatosaurus, Brontosaurus, cervical, cervical ribs, diplodocids, pneumaticity
6 Comments »

New paper out today: Aureliano et al. (2022) on vertebral internal structure in the earliest saurischians

December 9, 2022

Micro-computed tomography of the vertebrae of the basalmost sauropodomorph Buriolestes (CAPPA/UFSM 0035). (A) silhouette shows the position of the axial elements. Artist: Felipe Elias. (B), three-dimensional reconstruction of the articulated cervical vertebral series and the correspondent high-contrast density slices in (D–I). Diagenetic processes partially compromised the internal structures in these cervicals. (C), 3D reconstruction of the articulated anterior dorsal vertebrae and the correspondent high-contrast density slices in (J–M). Small circumferential chambers occur both ventrally in the dorsal centrum (J) and laterally in the neural arch pedicles (D). All images indicate apneumatic chaotic trabeculae architecture. Some of the latter develop into larger chambers in the centrum (E,J,K). Nutritional foramina are broader at the bottom of the neural canal in the posterior cervicals (F,G). All slices were taken from the approximate midshaft. Anterior views in (D–H,J,K). Lateral view in (L). Ventral view in (H,I,M). Anterior/posterior orientation was defined based on the axial position, not the anatomical plane. cc circumferential chamber, ccv chamber in the centrum, ctr chaotic trabecula, d diapophysis, ltr layered trabeculae, nc neural canal, nf nutritional foramen, s neural spine. Scale bar in (A) = 500 mm; in (B–M) = 10 mm. Computed tomography data processed with 3D Slicer version 4.10. Figures were generated with Adobe Photoshop CC version 22.5.1 X64. (Aureliano et al. 2022: fig. 4)

Here’s a nice early holiday present for me: 51 weeks after our first paper together, I’m on another one with Tito Aureliano and colleagues:

Aureliano, T., Ghilardi, A.M., Müller, R.T., Kerber, L., Pretto, F.A., Fernandes, M.A.,Ricardi-Branco, F., and Wedel, M.J. 2022. The absence of an invasive air sac system in the earliest dinosaurs suggests multiple origins of vertebral pneumaticity. Scientific Reports 12:20844. https://doi.org/10.1038/s41598-022-25067-8

As before, I’m in the “just happy to be here” last author position, and quite happy to be so, too. I’ve had a productive couple of years, mostly because my colleagues keep inviting me to write a little bit, usually about pneumaticity, in exchange for a junior authorship, and that’s actually a perfect fit for my bandwidth right now. That dynamic has let me work on some cool and varied projects that have broadened my experience in satisfying ways. But enough navel-gazing!

Also as before, Tito made a really nice video that explains our findings from the paper and puts them in their broader scientific context:

For a long time now I’ve been interested in the origin of postcranial skeletal pneumaticity (PSP) in dinosaurs and pterosaurs (e.g., Wedel 2006, 2007, 2009, Yates et al. 2012, Wedel and Taylor 2013) — or is that origins, plural? Tito and crew decided to take a swing at the problem by CT scanning presacral vertebrae from the early sauropodomorphs Buriolestes and Pampadromaeus, and the herrerasaurid Gnathovorax. (Off-topic: Gnathovorax, “jaw inclined to devour”, is such a badass name that I adopted it for an ancient blue dragon in my D&D campaign.) All three taxa have shallow fossae on the lateral sides of at least some of their presacral centra, and some neural arch laminae, so they seemed like good candidates in which to hunt for internal pneumatization.

I’ll cut right to the chase: none of three have internal pneumatic chambers in their vertebrae, so if there were pneumatic diverticula present, they weren’t leaving diagnostic traces. That’s not surprising, but it’s nice to know rather than to wonder. The underlying system of respiratory air sacs could have been present in the ancestral ornithodiran, and I strongly suspect that was the case, but invasive vertebral pneumatization evolved independently in pterosaurs, sauropodomorphs, and theropods.

Detail of the vertebrae and foramina of the basalmost sauropodomorph Buriolestes (CAPPA/UFSM-0035). Cervical (A–C), anterior (D–F) and posterior (G–I) dorsal vertebrae in right lateral view. Note that nutritional foramina are present throughout the axial skeleton (dark arrows). Anterior/posterior orientation was defined based on the axial position, not the anatomical plane. Scale bar = 5 mm. Figures were generated with Adobe Photoshop CC version 22.5.1 X64. (Aureliano et al. 2022: fig. 4).

Just because we didn’t find pneumaticity, doesn’t mean we didn’t find cool stuff. Buriolestes, Pampadromaeus, and Gnathovorax all have neurovascular foramina — small holes that transmitted blood vessels and nerves — on the lateral and ventral aspects of the centra. That’s also expected, but again nice to see, especially since we think these blood vessels provided the template for invasive vertebral pneumatization in more derived taxa.

The findings I’m most excited about have to do with the internal structure of the vertebrae. Some of the vertebrae have what we’re calling a pseudo-polycamerate architecture. The polycamerate vertebrae of sauropods like Apatosaurus have large pneumatic chambers that branch into successively smaller ones. Similarly, some of the vertebrae in these Triassic saurischians have large marrow chambers that connect to smaller trabecular spaces — hence the term ‘pseudo-polycamerate’. This pseudo-polycamerate architecture is present in Pampadromaeus, but not in the slightly older Buriolestes, which has a more chaotic internal organization of trabecular spaces. So even in the apneumatic vertebrae of these early saurischians, there seems to have been an evolutionary trajectory toward more hierarchially-structured internal morphology.

Micro-computed tomography of the vertebrae of the herrerasaurid Gnathovorax (CAPPA/UFSM-0009). (A) silhouette shows the position of the axial elements. Artist: Felipe Elias. (B) 3D reconstruction of the anterior cervical vertebra and the correspondent high-contrast density slices in (D-I). Diagenetic artifacts greatly compromised the internal structures. (C) 3D reconstruction of the articulated posterior cervical vertebrae and the correspondent high-contrast density slices in (J–O). Minerals infilled between trabecular vacancies generate reddish anomalies. All images indicate irregular, chaotic, apneumatic architecture. Note the apneumatic large chambers in the centrum (ccv) and the smaller circumferential chambers at the bottom (cc). All slices were taken from the approximate midshaft. Anterior views in (D,H,I). Right lateral view in (E,L,M). Ventral view in (F,G,J,K). cc circumferential chambers, ccv chamber in the centrum, ce centrum, ctr chaotic trabeculae, d diapophysis, dia diagenetic artifact, nc neural canal, nf nutritional foramen, poz postzygapophysis, prz prezygapophysis. Scale bar in (A) = 1000 mm; in (B–O) = 10 mm. Computed tomography data processed with 3D Slicer version 4.10. Figures were generated with Adobe Photoshop CC version 22.5.1 X64.

But wait, there’s more! We also found small circumferential chambers around the margins of the centra, and what we’re calling ‘layered trabeculae’ inside the articular ends of the centra. These apneumatic trabecular structures look a heck of a lot like the circumferential pneumatic chambers and radial camellae that we described last year in a dorsal vertebra of what would later be named Ibirania (Navarro et al. 2022), and which other authors had previously described in other titanosaurs (Woodward and Lehman 2009, Bandeira et al. 2013) — see this post.

So to quickly recap, in these Triassic saurischians we find external neurovascular foramina from the nerves and vessels that probably “piloted” the pneumatic diverticula (in Mike’s lovely phrasing from Taylor and Wedel 2021) to the vertebrae in more derived taxa, and internal structures that are resemble the arrangement of pneumatic camerae and camellae in later sauropods and theropods. We already suspected that pneumatic diverticula were following blood vessels to reach the vertebrae and produce external pneumatic features like fossae and foramina (see Taylor and Wedel 2021 for a much fuller development of this idea). The results from our scans of these Triassic taxa suggests the tantalizing possibility that pneumatic diverticula in later taxa were following the vascular networks inside the vertebrae as well. 

A morphological spectrum of vertebral structure, as I thought of it 15 years ago. The Triassic saurischians described in the new paper by Aureliano et al. 2022 would sit between Arizonasaurus and Barapasaurus. (Wedel 2007: text-fig. 8)

“Hold up”, I can hear you thinking. “You can’t just draw a straight line between the internal structure of the vertebrae in Pampadromaeus, on one hand, and Apatosaurus, or a friggin’ saltasaurine, on the other. They’re at the opposite ends of the sauropodomorph radiation, separated by a vast and stormy ocean of intermediate taxa with procamerate, camerate, and semicamellate vertebrae, things like Barapasaurus, Haplocanthosaurus, Camarasaurus, and Giraffatitan.” That’s true, and the vertebral internal structure in, say, Camarasaurus doesn’t look much like either Pampadromaeus or Ibirania — at least, in an adult Camarasaurus. What about a hatchling, which hasn’t had time to pneumatize yet? Heck, what about a baby Ibirania or Rapetosaurus or Alamosaurus? Nobody knows because nobody’s done that work. There aren’t a ton of pre-pneumatization baby neosauropod verts out there, but there are some. There’s an as-yet-unwritten dissertation, or three, to be written about the vascular internal structure of the vertebrae in baby neosauropods prior to pneumatization, and in adult vertebrae that don’t get pneumatized. If caudal 20 is the last pneumatic vertebra, what does the vascular internal structure look like in caudal 21?

Cervical vertebrae of Austroposeidon show multiple internal plates of bone separated by sheets of camellae. Bandeira et al. (2016) referred to those as ‘camellate rings’, Aureliano et al. (2021) called them ‘internal plates’, and in the new paper (Aureliano et al. 2022) we call similar structures in apneumatic vertebrae ‘layered trabeculae’. (Bandeira et al. 2016: fig. 12)

To me the key questions here are, first, why does the pneumatic internal structure of the vertebrae of titanosaurs like Ibirania — or Austroposeidon, shown just above in a figure from Bandeira et al. (2016) — look like the vascular internal structure of the vertebrae of basal sauropodomorphs like Pampadromaeus? Is that (1) a kind of parallelism or convergence; (2) a deep developmental program that builds vertebrae with sheets of bone separated by circumferential and radial spaces, whether those spaces are filled with marrow or air; (3) a fairly direct ‘recycling’ of those highly structured marrow spaces into pneumatic spaces during pneumatization; or (4) some other damn thing entirely? And second, why is the vertebral internal structure of intermediate critters like Haplocanthosaurus and Camarasaurus so different from that of both Ibirania and Pampadromaeus— do the pneumatic internal structures of those taxa reflect the pre-existing vascular pattern, or are they doing something completely different? That latter question in particular is unanswerable until we know what the apneumatic internal structure is like in Haplocanthosaurus and Camarasaurus, either pre-pneumatization (ontogenetically), or beyond pneumatization (serially), or ideally both. 

A Camarasaurus caudal with major blood vessels mapped on, based on common patterns in extant tetrapods. A list of the places where blood vessels enter the bone is also a list of places where sauropod vertebrae can possibly be pneumatized. We don’t think that’s a coincidence. From Mike’s and my presentation last December at the 3rd Palaeo Virtual Congress, and this post. (Wedel and Taylor 2021)

I was on the cusp of writing that the future of pneumaticity is vascular. That’s true, but incomplete. A big part of figuring out why pneumatic structures have certain morphologies is going to be tracing their development, not just the early ontogenetic stages of pneumatization, but the apneumatic morphologies that existed prior to pneumatization. BUT we’re also nowhere near done just doing the alpha-level descriptive work of documenting what pneumaticity looks like in most sauropods. I’ll have more to say about that in an upcoming post. But the upshot is that now we’re fighting a war on two fronts — we still need to do a ton of basic descriptive work on pneumaticity in most taxa, and also need to do a ton of basic descriptive work on vertebral vascularization, and maybe a third ton on the ontogenetic development of pneumaticity, which is likely the missing link between those first two tons.

I’m proud of the new paper, not least because it raises many, many more questions than it answers. So if you’re interested in working on pneumaticity, good, because there’s a mountain of work to be done. Come join us!

References

Posted by Matt Wedel
Filed in cross sections, CT, pneumaticity, prosauropod
4 Comments »

New paper: pneumatic diverticula in the neural canals of birds

March 29, 2022

Morphological variation in paramedullary airways; yellow = spinal cord, green = diverticula. The spectrum of variation is discretized into four groups: i, branches of intertransverse diverticula contact spinal cord at intervertebral joints; ii, branches of intertransverse diverticula extend partially into the vertebral canal, but remain discontinuous; iii, paramedullary diverticula form sets of tubes that are continuous through vertebral canals of at least two consecutive vertebrae; iv, continuous paramedullary diverticula anastomose with supravertebral diverticula. Each variant is depicted diagrammatically (A, dorsal view; B, E, H, & K, transverse view) and shown in two CT scans; images in each column correspond to the same morphology. Morphology i: C, cormorant; D, scrub jay. Morphology ii: F, bushtit; G, common murre. Morphology iii: I, red-tailed hawk; J, black-crowned night heron. Morphology iv: L, M, pelican. (Atterholt and Wedel 2022: figure 5)

New paper out:

Atterholt, Jessie, and Wedel, Mathew J. 2022. A computed tomography-based survey of paramedullary diverticula in extant Aves. The Anatomical Record, 1– 22. https://doi.org/10.1002/ar.24923

Quick aside, which will soon be of historical interest only: so far, only the accepted-but-unformatted manuscript is available, with the final, fully-formatted ‘version of record’ due along at some point in the future. We’re not sure when that will be — could be next week, could be months from now — which is why I’m following my standard procedure and yapping about the new paper now. This has paid off in the past, when papers that were only available in accepted ms form were read and cited before the final version was published. UPDATE on April 9: the formatted version of record is out now, as an open-access article with a CC-BY license, and I swapped it for the ‘accepted ms’ version in the links above and at the end of this post.

This paper has had a weirdly drawn-out gestation. Jessie and I hatched the idea of it way back in 2017, when we were teaching in the summer anatomy course together. I learned that Jessie had a big war chest of CTs of dead birds, and I’d been obsessed with supramedullary diverticula in birds and sauropods for some time already (e.g., an SVPCA talk: Wedel et al. 2014). There were detailed published descriptions of the supramedullary diverticula in a handful of species — namely chickens, turkeys, and pigeons — but no broad survey of those diverticula across living birds. Jessie had the CT scans to do that big survey, which we got rolling on right away. She presented our preliminary results at SVPCA in 2018 (Atterholt and Wedel 2018), and by rights the paper should have been along shortly thereafter. More on that in a sec.

One thing that may seem odd: we use the term ‘paramedullary diverticula’ instead of the more familiar and established ‘supramedullary diverticula’. That’s because these diverticula are not always dorsal to the spinal cord; sometimes they’re lateral, sometimes they’re ventral, and sometimes they completely surround the spinal cord, like an inflated cuff. So we decided that the term ‘paramedullary’, or ‘next to the spinal cord’, was more accurate than ‘supramedullary’, or ‘above the spinal cord’, for describing this class of diverticula.

Observed variation in the shape, arrangement, and orientation of paramedullary diverticula relative to the spinal cord; yellow = spinal cord, green = diverticula. A, paired diverticula dorsal to spinal cord in an ostrich. B, paired diverticula lateral to spinal cord in a bushtit. C, paired diverticula ventral to spinal cord in a violet turaco. D, three diverticula dorsal to spinal cord in an ostrich. E, four diverticula dorsal to spinal cord in an eclectus parrot. F, single, c-shaped diverticulum dorsal to spinal cord in an ostrich. G, diverticula completely surrounding spinal cord and pneumatizing vertebra in a violet turaco. H, no paramedullary diverticula present in a Pacific loon. I, diverticula completely surrounding spinal cord in a pelican. (Atterholt and Wedel 2022: figure 6)

I will have more to say about the science in other posts, and you can get the scientific backstory in this post and this one and the abstracts cited above and linked below. The rest of this post is mostly about me, so if you stick around, buckle up for some advanced navel-gazing.

There’s no one reason why this paper didn’t come out sooner. In short, I hit a wall. We went through a curriculum change at work, and suddenly the annual schedule that I’d relied on for a decade was completely upended. I had some unexpected challenges in my personal life. But the biggest problem was that my attitude toward research and writing had changed, for the worse.

When I was fresh out of grad school I had this kinda snotty attitude that my research was MINE, and wherever I was teaching was just, like, a paycheck, man, but they don’t own me, or my research. And as my teaching and committee responsibilities ramped up I still felt like research and writing was something I did for myself, and that my mission was to steal however many hours I could away from the “day-job work” to get done the things that I really wanted to do. Like a guerilla insurgency. In retrospect, it was a pretty good attitude for getting stuff done.

But somewhere along the way, I stopped thinking about research as something that belonged to me, something that I did for myself, and started thinking about it as part of my job. (This also maybe is not so flattering in what it reveals about how I think, or at least thought, about my job.) Instead of using my research time as a source of energy and a wellspring of satisfaction and positivity, I starting thinking of it only as a sink. And it happened so insidiously that I didn’t even realize it. My productivity plummeted, and I didn’t understand why. I was restless and depressed, and I didn’t understand that either. At the level of my superficial thoughts I still wanted to get research done, but my subconscious was turned off to it, so I just spun my wheels.

Then the pandemic hit. I’d always been a pretty optimistic, upbeat person, but I found myself just staring off into space franticizing about all the horrible things going on in the world, or staying up too late doom-scrolling the news. I slept too little, and poorly, and by the end of 2020 I felt worn down to a nub.

Osteological evidence of paramedullary diverticula. A, pocked texturing inside the vertebral canal of a pelican (LACM 86262). B, pneumatic foramen on the roof of the vertebral canal of an albatross (Phoebastria nigripes, LACM 115139). C, pneumatic foramina in the floor of the vertebral canal of an ostrich (Struthio camelus, LACM 116205). D, deep pneumatic fossae in the roof of the vertebral canal of an Eastern moa (Emeus sp., LACM unnumbered). (Atterholt and Wedel 2022: figure 7)

Then a series of positive things happened:

  • I received a long, heartfelt email from Jessie (fittingly!), asking after me and laying out a plan for getting the paper done and out. It was the kick I needed to look inside and start picking myself apart, to figure out what the heck was going on. Much of this post is cribbed from my reply to her.
  • I got a little break from lecturing in the spring of 2021, and that gave me the space to get a couple of things finished and submitted — the pneumatic variation paper with Mike in January (Taylor and Wedel 2021), and the Haplocanthosaurus neural canal paper, which was submitted even earlier in January, although it came out much later (Wedel et al. 2021; more on that publication delay in a future post).
  • Finally, I had young, energetic coauthors who were moving projects forward that required modest levels of effort from me, but which paid off with highly visible publications that I’m proud to be an author on, including the saltasaur pneumaticity paper (Aureliano et al. 2021) and the ‘Sauro-Throat’ paper (Woodruff et al. 2022).

It’s impossible to overstate how energizing it was to get new things done and out, and how much it helped to have collaborators who were putting wins on the board even when I was otherwise occupied. One of those collaborators was Jessie, who just kept pushing this thing forward — and, sometimes, pushing me forward — until it was done. So the paper you can read today is a testament not only to her acumen as a morphologist, but also to her tenacity as a scholar, and as a friend.

The part of the paper I’m happiest about is the “Conclusions and Directions for Future Research”, which points the way toward a LOT of further studies that need to be done, both on extant birds and on fossil archosaurs, ranging from bone histology to functional morphology to macroevolution. As we wrote in the concluding sentence of the paper, “We hope that this study serves as a foundation and an enticement for further studies of this most unusual anatomical system, in both extinct and extant archosaurs.”

I can’t wait to see what comes next.

References

Posted by Matt Wedel
Filed in CT, just like ALL the birds, navel blogging, new papers, papers by SV-POW!sketeers, pneumaticity, stinkin' theropods, supramedullary diverticula, Uncategorized
2 Comments »

Things to Make and Do, part 31: redneck CT-scan

March 3, 2022

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

 

Posted by Mike Taylor
Filed in cervical, pneumaticity, T2M&D, turkey
11 Comments »

Fossae/foramina in the articular surfaces of turkey vertebrae

February 21, 2022

I was looking more closely at the turkey skeleton from my recent post, and zeroed in on the last two dorsal (= thoracic) vertebrae. They articulate very well with each other and with the first vertebra of the sacrum, with the centra and zygapophyses both locking in so that there can only have been very little if any movement between them in life. Here they are, in right lateral view:

Last two dorsal (= thoracic) vertebrae of a mature domestic turkey Meleagris gallopavo domesticus, in right lateral view.

Before we move on, it’s worth clicking through to the full-size version of this image and wondering at both the quality of modern phone cameras (a Pixel 3a in this case) and the variety of textures on these little bones. There is smooth, finished bone on the sides of the neural spines; very fine pits and bumps on the zygapophyseal facets where the thin layer of hyaline cartilage attached; rougher texture in the parapophyseal facets where thicker cartilage attached; and very rough texture on the ends of the transverse processes, where there was relatively thick cartilage.

And there is, unsurprisingly in a bird, pneumaticity everywhere. In the more anterior vertebra alone (to the right) the photo shows pneumatic openings (from bottom to top) low on the centrum (below the parapophysis), high on the centrum (below the lateral process),  in the hollow between the lateral process, the posyzyg and the centrum, on the lateral surface of the prezygapophyseal ramus, and on the rear surface of the lateral process. There are others that are obscured in this photo, including on top of the lateral process where it meets the neural spine. Here they are, pointed out for you (with the hidden one shown translucently):

Last two dorsal (= thoracic) vertebrae of a mature domestic turkey Meleagris gallopavo domesticus, in right lateral view. Pneumatic openings on penultimate vertebra highlighted with red lines; obscured opening above lateral process shown as translucent.

OK, that was the B-movie. Now to the main feature. The next photo shows the same two vertebrae, folded away from each other so that we see the anterior face of the posterior vertebra (on the left) and the posterior face of the anterior vertebra (on the right).

Last two dorsal (= thoracic) vertebrae of a mature domestic turkey Meleagris gallopavo domesticus. Left: last dorsal vertebra in anterior view; right: penultimate dorsal vertebra in posterior view.

Again, do click through to see the exquisite detail, especially the complex of pneumatic features on the anterior face of the neural spine of the last dorsal (on the left) and on the posterior face of the left lateral process of the penultimate dorsal (on the right).

And … in the articular facets of the centra?

Seriously, what the heck is going on here? It doesn’t make sense  that there would be pneumatic openings in articular surfaces, because by definition something else (in this case the adjacent vertebra) is abutted hard up against then, so there is no way for a diverticulum to get in. For the same reason, you don’t get vascular foramina in articular surfaces because there is no way to get an artery in there. And there is no hint in these vertebrae of channels along either articular surface that diverticula or arteries could  possibly have laid in.

And yet, there those big openings are. What are they?

I discussed this with Matt, in case it’s Well Known Phenomenon that I’d somehow not heard about but it seems it is not. What we know for sure is that these openings are present, and that they are not mechanical damage inflicted during preparation. So what are they?

What else even is there for them to be? What penetrates bone apart from diverticula and blood vessels? Nerves follow the blood vessels, so it can’t be nerves in the absence of blood vessels.

By the way, there are similar but smaller openings in the posterior face of the last dorsal (the one on the right in the photo), but none anywhere else along the postcervical column: not on the anterior surface of the penultimate dorsal, not on the front or back of the sacrum, and not in any of the other dorsals.

One possibility we considered is that the vertebrae were locked together in life and that a pneumatic space inside the centrum of the last dorsal worked right through into the penultimate one. But that doesn’t work: the openings are not aligned. Also, those in the penultimate dorsal are definitely blind (i.e. they do not connect to deeper internal air-spaces) and those in the last dorsal probably are, too.

We do not know what is going on here.

Help us! Is this kind of thing common in turkeys? Have people seen it in other taxa? Do we know what it is?

Posted by Mike Taylor
Filed in dorsal, help SV-POW!, pneumaticity, turkey
14 Comments »

Sauro-throat, Part 3: what does Dolly’s disease tell us about sauropods?

February 17, 2022

Naturally I was grateful when Cary invited me to be part of the team working on Dolly, the diplodocid with lesions in its neck vertebrae (Woodruff et al. 2022; see previous posts on Dolly here and here). I was also intellectually excited, not only to see air-filled bones with obvious pathologies, but also for what those pathologies could tell us about Dolly and other sauropods. That’s the part of our new paper I want to unpack in this post.

We have a lot of evidence that air-filled bones in birds are a good model for air-filled bones in extinct dinosaurs. And we have several lines of evidence (not just air-filled bones; see Schachner et al. 2009, 2011, 2020) that the respiratory systems of many dinosaurs functioned broadly like those of living birds. But we have less direct evidence than we’d like, so every additional bit of information is welcome.

Diving into Diverticula

In birds, the air-filled bones in the neck and body are connected to the respiratory system by air-filled tubes. These tubes sometimes get called air sacs, in the sense that they are sacs filled with air, but we also refer to them pneumatic diverticula, to distinguish them from the respiratory air sacs in the torsos of birds that ventilate the lungs. Imagine blowing up some rubber gloves and sticking them inside a bird* and you’ll have a pretty good mental model of the system — the inflated ‘palm’ area of each glove is like one of the respiratory air sacs, the air-filled glove fingers are the diverticula, and the rubber material of the glove is the pneumatic epithelium that lines the air sacs and the diverticula alike. 

* Please don’t actually try that.

The cartoon above presents an unrealistically simplified picture of the respiratory system in dinosaurs and birds. For one thing, I omitted the windpipe or trachea — that blue tube going up the neck represents the diverticula that run alongside, and often inside, the neck vertebrae, parallel to the trachea but separated from it by whole sheets of muscle. Also, the cartoon only shows diverticula of the air sacs, but diverticula can also originate from the lungs themselves (see O’Connor 2006: 1211 and Schachner et al. 2020: 16-19). Here’s the actual respiratory system of a pigeon, with the trachea and lungs in pink and the air sacs and their diverticula in blue (Muller 1908 fig. 11):

I think it’s pretty natural to look at that illustration and wonder where the heck the guts go, since it certainly looks like the air sacs are occupying the entire volume of the torso. The answer is that the air sacs enclose the viscera “as do the shells of a nut”, in the memorable formulation of Wetherbee (1951: p. 243), describing the air sacs of the English sparrow.


Fig. 4. Reconstruction of the distribution of pneumatic diverticula in diplodocids and dicraeosaurids. A. Schematic drawing of midcervical vertebra of Diplodocus in left lateral aspect (A1), in dorsal aspect with single neural spine (A2) and in dorsal aspect with bifurcate neural spine (A3). The partitioning of pneumatic diverticula at the lateral surface of the vertebral corpus is hypothetical, based on the strongly divided pneumatic fossae. Schwarz et al. (2007: fig. 4A).

Furthermore, the pneumatic diverticula around the vertebrae in birds are complex, and we are fairly certain that they were also complex in sauropods, because they left so many distinct traces. The most detailed reconstructions of the cervical diverticula in sauropods that I know of are those of Daniela Schwarz and colleagues (2007), as shown above. For what it’s worth, I think those reconstructions are not just reasonable but perhaps conservative; I think there’s a good chance that the diverticular network around the vertebrae was even more complex and extensive. 

The rubber-glove model also lets us see that the diverticula are cul-de-sacs. We know that diverticula can anastomose, or merge, to form networks, and there is a possibility that if diverticula from different air sacs anastomosed, different pressures in those air sacs might allow some air to circulate through the diverticular network. Maybe — the anterior and posterior air sacs fill and empty at the same time, so there might not be a pressure differential to exploit. If air circulates in the diverticula at all in birds, it probably happens in the dorsal vertebrae, where diverticula from different parts of the respiratory system have the best opportunity to anastomose. But the far ends of the diverticular network are always dead ends, and we assume that air diffuses in and out of those terminal diverticula fairly slowly. We’re stuck with assumptions because no-one’s ever checked, experimentally, to determine the rate of diffusion or circulation of air in the diverticula. But it’s hard to imagine much circulation in the terminal diverticula, with no air reservoir or pump at the far end.

Reconstruction of soft−tissues in the neck of Diplodocus. A. Transverse cross−sections through cervical vertebra with bifurcate neural spine in the diapophysis region (A1) and in caudal third of vertebra (A2). B. Transverse cross−sections through cervical vertebra with single neural spine in diapophysis region (B1) and in caudal third of vertebra (B2), dashed outlines representing possible craniocervical extensor muscle analogous to m. biventer cervicis of extant birds or m. transversospinalis capitis of extant crocodylians. Schwarz et al. (2007: fig. 7A-B).

Here’s another great illustration from Schwarz et al. (2007), showing cross-sections of the neck of Diplodocus with hypothetical soft tissues restored. Bone is black, muscle is pink, and the pneumatic diverticula are blue. As this diagram makes clear, the air spaces in the bones are themselves extensions of the diverticula (that much is true regardless of how extensive we make the reconstructed diverticula outside the vertebrae). Instead of smooshing an inflated rubber glove into a duck, imagine smooshing one into a vertebra of a duck — or a Diplodocus — so that all of the empty spaces are occupied by some blobby bit of inflated-glove finger. All of air spaces in the bone would be lined by rubber-glove material, which in this metaphor is the same pneumatic epithelium that lines both the respiratory air sacs and their pneumatic diverticula, outside the bones or inside them.

I get to see this firsthand in the gross anatomy lab in our unit on head and neck anatomy. As we open up the skulls of the cadavers, the air-filled epithelial balloons that fill the sinuses sometimes pull away from, or completely out of, their bony recesses. (I’ll bet I could demonstrate the same thing with the sinuses of a pig or sheep head — I should give that a shot and post the resulting photos or videos here.) The point is, the pneumatic epithelium is in intimate contact with the bone, lining every pneumatic fossa, foramen, and internal chamber; this will be really important later on.

Incidentally, one question I get a lot is whether the diverticula, inside or outside the bones, contributed to gas exchange in sauropods. The answer is, probably not. We know from dissections and histological work on birds that the respiratory air sacs, their diverticula, and the diverticular spaces inside the skeleton are all relatively avascular, meaning that the tissues get enough blood to stay alive, but aren’t specialized for gas exchange. Furthermore, physiological experiments on living birds have shown that about 95% of the gas exchange happens in the lungs, and almost all of the remaining 5% happens in the paired abdominal air sacs (Magnussen et al. 1976), probably because they are so large and so intimately in contact with the guts (Wetherbee’s nutshell metaphor), which are well-supplied with blood. We also know from bone histology that the air-filled bones of extinct dinosaurs are essentially identical to those of modern birds (Lambertz et al. 2018), so there’s no evidence that they functioned any differently.

A simplified diagram of the sauropod respiratory system. What I’ve labeled “air tubes” here are the pneumatic diverticula. Air holes in the vertebrae are also known as pneumatic foramina. The shapes of the lungs and air sacs are speculative, but the minimum extent of the pneumatic diverticula is not–although it could be an underestimate (e.g., diverticula might have gone even further down the tail, and just not left any diagnostic traces on those vertebrae).

A final piece before we get back to Dolly: we know from lots of anecdotal observations, and some actual experiments, that air-filled bones have to stay connected to the outside to form in the first place, and to stay healthy afterward. This is true of both human sinuses and postcranial pneumatic bones in birds, so it’s reasonable to assume that it’s a general feature of all air-filled bones (see Witmer 1997 for lots of relevant citations and discussion). This is a pretty handy thing to know, because if we find an air-filled vertebra way out in the tail, we know pneumatic diverticula of the respiratory system got at least that far. ‘At least’ because pneumatic diverticula can make diagnostic traces on bones, but they don’t always do so. That means that the diverticular network can easily be more extensive than its skeletal traces, but not less so — see Wedel and Taylor (2013) for more on that.

To sum up, we suspect the following things about pneumatic diverticula around the vertebrae of sauropods, including Dolly:

  1. The diverticula were complex, based on the traces they left on the bones, and similarly complex diverticula in birds.
  2. The diverticula were patent, or open, maintaining an open connection to the outside by way of the respiratory air sacs, lungs, and trachea, because that’s how air-filled bones work in living birds and mammals.
  3. Despite being complex and ultimately open to the outside in one direction, the diverticula were cul-de-sacs, with little or no active circulation of air — especially in the neck.

With that in mind, what does the distribution of infected bone in Dolly tell us about sauropods?

Infections and inferences

Here’s another illustration of the respiratory system of the pigeon, this time a dorsal or top-down view, from Muller (1908: fig. 12):

Okay, that was a bit of a bait-and-switch: I promised you Dolly and gave you another pigeon. But that’s only to help you understand this similar cartoon I drew, which represents Dolly’s respiratory system and neck vertebrae, also seen from the top down:

Like the earlier cartoon, this is pretty simplified. For instance, I got lazy and didn’t draw all of the neck vertebrae. In life, Dolly probably had 15 or 16 neck vertebrae, like other diplodocids, and we know that the three with lesions are C5-C7 because they were found articulated. Here I drew just enough vertebrae to make my points, and I left off the head and all the other extraneous bits. Also, I’ve drawn the diverticula that run up the neck originating from cervical air sacs, as in pigeons (Muller 1908), but there is evidence that in ostriches those diverticula may originate from the lungs themselves (Schachner et al. 2020). Whether the diverticula come from the lungs or the air sacs is probably not an answerable question for sauropods, and for my purposes here, it doesn’t matter, only that the diverticula are connected back to the core respiratory system.

Three things struck us about the distribution of the infected bone in Dolly’s neck:

  1. The lesions are all in vertebrae that are a long way up the neck, far from the lungs and respiratory air sacs in the torso.
  2. The lesions are clustered in serially-adjacent vertebrae, instead of being scattered up and down the neck randomly.
  3. The lesions are present bilaterally, on both left and right sides of the affected vertebrae.

Well, as opposed to what? We can imagine a scenario in which the lesions were scattered randomly, not just up and down the neck, but also on left and right sides, like so:

If the infection had been carried in the blood, we might expect such a random pattern. In that case, it would be an extreme coincidence if a blood-borne infection, which could go anywhere in the body, only manifested in the air spaces on the sides of three consecutive vertebrae. The clustering of the Dolly’s lesions, in the air spaces on both sides in three adjacent vertebrae, far up the neck, points to a different cause.

Recall that diverticula are lined by epithelium, and that in air-filled bones, the epithelium is right up against the bone tissue. The infection in Dolly almost certainly started out as an infection in the diverticulum, which was so severe that it spread to the underlying bone. In exactly the same way that the air spaces in the bones are the skeletal footprints of the diverticula, the lesions in Dolly’s vertebrae are the skeletal footprints of infected epithelium lining the diverticula, like so:

The infection may have gotten so severe, far up Dolly’s neck, precisely because there was little airflow so far from the lungs and air sacs. Airborne bacteria or fungal spores could have floated into the diverticula by diffusion, come to rest against the epithelium in warm, dark, humid conditions, and gone wild. It’s also possible that a huge swath of Dolly’s respiratory system was infected, but the infection only got severe enough to spread to the underlying bone in cervical vertebrae 5-7, in which case the actual infection might have looked something like this:

Just like a diverticulum can contact a bone without producing a distinct trace, the pneumatic epithelium could be infected without producing a bony lesion. Thought experiment: how many times have you had a sinus infection, and how many people do you know who have had sinus infections? And how many of those sinus infections were severe enough, and lasted long enough, to produce bony lesions like we see in Dolly? Probably very few — such things do happen in humans, and the medical literature has plenty of cases (and if this has happened to your or a loved one, you have my full sympathy) — but on a population level, the fraction of respiratory infections that produce bony lesions is miniscule. Similarly, it’s very likely that much more of Dolly’s respiratory system was infected than we can tell from the skeleton.

A cervical vertebra of an ostrich with some of the pneumatic diverticula traced on.

The presence of infected bone on both left and right sides of C5-C7 in Dolly is also telling. If the diverticula on the left and right sides of the neck were separate, the symmetrical pattern of infection would be another extreme coincidence. But in birds there are opportunities for diverticula from the left and right sides of the neck to meet and anastomose, especially the supravertebral diverticula on the neural arch (shown above), and the supramedullary diverticula inside the neural canal. Based on pneumatic traces on the vertebrae we infer that the same diverticula were present in sauropods, as shown up above in the Diplodocus figures from Schwarz et al. (2007), and those left-and-right communications probably allowed the infection to develop more or less symmetrically. Or to put it another way, the symmetrical infections are additional evidence that the diverticula on the left and right sides of the neck were connected across the midline, and birds show that there are several ways that could have happened.

CT scans of cervical 7 of MOR 7029. Photograph and scan model of the vertebra ((A,B) respectively). The colored lines in (B) correspond to the scan slices (and scan interpretative drawings below). White arrows point to the external feature, while black arrows denote the hyperintense bone and irregular voids. (C) Comparison of the abnormal tissue composition of MOR 7029 (left), compared to that of a ‘normal’ diplodocine (right). Text and white arrows indicate the various features different shared/differentiated between the two. For the interpretative drawings, white = ‘normal’ bone, grey = hyperintense bone, black = irregular voids. Woodruff et al. (2022: fig. 2).

Another possibility is that a good chunk of the internal structure Dolly’s vertebrae was infected, and the lesions that we see on the surface are just the groady tips of big, disgusting icebergs of infected bone. In fact, that’s pretty much what the CT scans show. So possibly the infection started on one side of each vertebra and basically burrowed through to reach the other side. That would probably take weeks or months, whereas the infection could have spread across the midline through diverticula in hours or days, so I think the latter scenario is still the most plausible explanation for the presence of the lesions on both sides of the affected vertebrae.

In summary, I don’t think Dolly tells us anything surprising that we didn’t suspect before. Rather, the pattern of infection in Dolly makes perfect sense if the diverticula of sauropods were essentially bird-like, and that pattern is difficult to explain any other way.

Finding skeletal traces of a respiratory infection in Dolly was still a crazy lucky break, and that’s something I’ll discuss more in the next post in this series.

References

Posted by Matt Wedel
Filed in diplodocids, Dolly, paleopathology, pigeon, pneumaticity, stinkin' theropods
8 Comments »

New paper: Dolly, the dinosaur with a sauro-throat

February 10, 2022

I was at the SVP meeting in Albuquerque in 2018 when Cary Woodruff called me over and said he had something cool to show me. “Something cool” turned out to be photos of infected sauropod vertebrae from the Morrison Formation of Montana. Specifically, some gross, cauliflower-looking bony lesions bubbling up in the air spaces on the sides of the vertebrae.

Pathologic pneumatic tissue in MOR 7029. (A) Schematic map of the neck of Diplodocus (Hatcher 1901; bones not present in grey), with the pathologic structures denoted in red. (B) Cervical 5 of MOR 7029 with red box highlighting the pathologic structure; close up in (C) with interpretative drawing in (D) (by DCW) (pathology in red). Woodruff et al. (2022: fig. 1).

I was stoked, because I’ve been working on air-filled bones in sauropods since 1998, and in that time I’ve gotten countless versions of this question: “Do you ever see any evidence of respiratory infections in those air spaces?” For 20 years, the answer had been ‘no’, but now Cary was showing me a likely ‘yes’.

Better still, Cary asked me if I wanted to collaborate on writing up the case. He could have done it on his own, but right out of the gate he wanted to assemble a collaborative team. He also got paleopathologist and veterinarian Ewan Wolff, veterinary radiologist Sophie Dennison, and anatomist and paleontologist Larry Witmer. It was my first time collaborating with all of those folks, and it was really cool firing around ideas, observations, and references. Cary coined the clever title “Sauro-Throat” when we presented our preliminary results at SVP (Woodruff et al. 2020), and you’ll probably see it a lot in conjunction with this paper.

The elaborate and circuitous pulmonary complex of the sauropod, with the hypothetical route of infectious pathway in MOR 7029. Skeletal reconstruction of the diplodocine Galeamopus pabsti by and copyright of Francisco Bruñén Alfaro to scale with MOR 7029. Human scale bar is the exemplar of pandemic education and rationalism, Dr. Anthony Fauci, at his natural height of 170 cm. Woodruff et al. (2022: fig. 3).

A little over three years after our meet-up in Albuquerque, one global pandemic notwithstanding, our results are out this morning in Scientific Reports (Woodruff et al. 2022). Normally I’d write a mini-dissertation about our findings, but I decided to do a little video explainer instead. That’s the video linked up top — many thanks to Fiona Taylor (music), Brian Engh (paleoart), and Jennifer Adams (filming and editing) for the timely help in getting it done.

I’ll have more to say about this in the future. For now, the paper is a free download at this link. Go have fun!

UPDATE later the same day:

Woo-hoo! Dolly is the top science story on Google News:

Google News UK:

The Guardian — with fabulous quotes by Steve Brusatte and, especially, Mike Benton:

…and probably others, but that’s enough navel-gazing for one afternoon.

References

Posted by Matt Wedel
Filed in cervical, diplodocids, Dolly, paleopathology, pneumaticity
25 Comments »

Here’s a video on the new saltasaur pneumaticity paper by Aureliano et al. (2021)

December 18, 2021

This is super cool: my friend and lead author on the new saltasaur pneumaticity paper, Tito Aureliano, made a short (~6 min) video about the fieldwork that Aline Ghilardi and Marcelo Fernandes and their team — many of whom are authors on the new paper — have been doing in Brazil, and how it led to the discovery of a new, tiny titanosaur, and how that led to the new paper. It’s in Portuguese, but with English subtitles, just hit the CC button.

Previous post:

Reference

 

Posted by Matt Wedel
Filed in pneumaticity, titanosaur, video
3 Comments »

New paper out today: Aureliano et al. (2021) on exquisite pneumaticity in a tiny titanosaur

December 17, 2021

Posterior dorsal vertebra of the Upper Cretaceous nanoid saltasaurid LPP-PV-0200. Three-dimensional reconstruction from CT scan in left lateral view (A). Circle and rectangle show sampling planes and the respective thin sections are in (B,C). ce centrum, ns neural spine, pn pneumatopore, poz postzygaphophysis, prz prezygapophysis. Scale bar in (A) 10 cm; in (B,C) 1 cm. Computed tomography data processed with 3D Slicer version 4.10.

Well, this is a very pleasant surprise on the last day of the semester:

Tito Aureliano, Aline M. Ghilardi, Bruno A. Navarro, Marcelo A. Fernandes, Fresia Ricardi-Branco, & Mathew J. Wedel. 2021. Exquisite air sac histological traces in a hyperpneumatized nanoid sauropod dinosaur from South America. Scientific Reports 11: 24207.

You may justly be wondering what I’m doing on a paper on a South American titanosaur. It came about like this:

  • I wrote to Tito Aureliano back in March to congratulate him on his 2019 paper, “Influence of taphonomy on histological evidence for vertebral pneumaticity in an Upper Cretaceous titanosaur from South America”, which I’d just reread, and was impressed by;
  • he told me he was working on a manuscript on saltasaur pneumaticity and would be grateful for my thoughts;
  • I sent him said thoughts, with no strings attached;
  • he asked me if I’d be willing to come on the project as a junior author;
  • I said yes;

and a few months later, here we are.

Dorsal vertebra internal structures of LPP-PV-0200. Reconstructed tomography model in distal (A) and right lateral (B) views illustrating subvertical tangential CT scan slices in false color (1–9). Images show that only a few structures had survived diagenesis which restricted the assessment of the internal architecture to limited spaces. Lighter blue and green indicate lower densities (e.g., pneumatic cavities). Purple and darker blue demonstrate denser structures (e.g., camellate bone). Dashed lines indicate internal plates of bone that sustain radial camellae. ce centrum, cc circumferential chambers, cml camellae, hc-cml ‘honeycomb’ camellae, ns neural spine, pf pneumatic foramen, pn pneumatopore, pacdf parapophyseal-centrodiapophyseal fossa, pocdf postzygapophyseal-centrodiapophyseal fossa, rad radial camellae. Computed tomography data processed with 3D Slicer version 4.10.

My correspondence to Tito basically boiled down to, “All the things you’ve identified in your CT scans are there, but there are also a few more exciting things that you might want to draw attention to” — specifically circumferential and radial camellae near the ends and edges of the centrum, and pneumatic chambers communicating with the neural canal, which were previously only published in Giraffatitan (Schwarz and Fritsch 2006; see Atterholt and Wedel 2018 and this post for more). The internal plates of bone inside the cotyle, which help frame the radial camellae, were first noted by Woodward and Lehman (2009), and discussed in this post.

I can’t think of any reason not to just post the notes I sent to Tito back in March, so here you go:

Wedel suggestions for Aureliano et al Saltasauridae dorsal

I may have more to say about this in the coming days, but at the moment I have two extant dinosaurs — ducks, to be precise — smoking on the grill, and I need to get back to them. The new paper is open access, free to the world (link), so go have fun with it.

UPDATE the next day: here’s another post on the new paper:

References

Posted by Matt Wedel
Filed in dorsal, histology, open access, papers by SV-POW!sketeers, pneumaticity, supramedullary diverticula, titanosaur
3 Comments »
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