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
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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
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Human anatomy: advice on studying for practical exams

December 10, 2021

Here’s another “blogging this so I can stop retyping it in emails to students” post. 

Relevant to all anatomy practical exams:

  • Every time you approach a cadaver/station, get your orientation down first. Muscles, nerves, and vessels are always on their way from one place to another, and knowing the orientations of those individual structures is critical, but useless if you don’t take the time to grasp the overall orientation of the body, or body region.
  • Related to the above: draw. Draw, draw, draw. Not only to help fix structures in your head, but (probably even more critically) to get orientations down. For example, in the infratemporal fossa the maxillary artery is going from posterior and inferior to anterior and superior, whereas the big branches of the mandibular division of the trigeminal nerve (V3) are mostly angled from posterior and superior to anterior and inferior. One nice thing: the drawings don’t have to be good; even stick figures are useful, and for learning orientations simple diagrams are arguably even better than complex ones.
  • Think about possible distractors regionally as well as systemically. Here’s what I mean: when people miss items on practical exams, often it is not because they confused one nerve for another nerve (systemic thinking), but because they confused a nerve for an artery, or a muscle for a gland, or a tendon for a duct, that happened to be in the same area (regional thinking). Whatever structure you are focused on learning, be aware of all the other structures in the same area, regardless of whether they look like plausible distractors or not — in the heat of the moment, it’s all too easy to pick something in the same region, even if it’s not the same type of structure (artery, vein, nerve, muscle, gland, duct, etc.). It may sound unlikely in the cold light of day — how does one confuse a gland and a muscle? — but the pressure of an anatomy practical has strange effects on the human brain (MJW, pers. obs.).

Relevant to head and neck anatomy specifically:

  • Think about all the places that the various cranial nerves are visible. Make a table cross-referencing all the dissections and all the cranial nerves, so you can see which cranial nerves are visible in which dissections (which views of the head and neck, once the dissections are completed). For example, if I want to tag the hypoglossal nerve on a practical exam, there are potentially five places I can do that: (1) coming off the brainstem; (2) inside the skull, going through the hypoglossal canal; (3) outside the skull, coming out of the hypoglossal canal, or in the deep neck, on the posterior aspect of the pharynx; (4) in the anterior neck, where it arcs below the posterior belly of the digastric muscle; or (5) in the oral cavity, coming into the posterolateral aspect of the tongue. 

Of course, all of this advice presumes that you’re already doing the basic stuff, like studying actively and spending as much time as possible in the lab. If not, read this and do that stuff, too.

Finally, remember that it’s never too late for good study habits to be useful. Even if you put it off until the evening before an exam, a few hours of organized, active studying (plus as many hours of sleep as you can manage) will help you more than frantically cramming all night.

Posted by Matt Wedel
Filed in human anatomy
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Pneumatization sites: how does air get into vertebrae?

December 8, 2021

Science doesn’t always get done in the right order.

In the course of the research for my paper with Mike this past spring, “Why is vertebral pneumaticity in sauropod dinosaur so variable?”, published in Qeios in January, I had a couple of epiphanies. The first was that I had collated enough information to map the sites at which arteries and veins enter and exit the vertebrae in most tetrapods. The second was that, having done that, I’d also made a map of (almost) all the places that diverticula enter the vertebrae to pneumatize them. This is obviously related to the thesis we laid out in that paper, that postcranial skeletal pneumaticity is so variable because pneumatic diverticula follow pre-existing blood vessels as they develop, and blood vessels themselves are notoriously variable. In fact, if you had to summarize that thesis in one diagram, it would probably look like the one above, which I drew by hand in my research notebook in early March.

Only that’s not quite correct. I didn’t have those epiphanies “in the course of the research”, I had them after the pneumatic variation paper was done and published. And at the time they felt less like epiphanies and more like a series of “Holy crap” realizations:

  1. Holy crap, that diagram would have been really helpful when we were writing the pneumatic variation paper, since it establishes, almost tautologically, that diverticula invade vertebrae where blood vessels already have. In a rational world, Mike and I would have done this project first, and the pneumatic variation paper would have stood on its shoulders.
  2. Holy crap, how have I been working on vertebral pneumaticity for more than two decades without ever creating a map of all the places a vertebra can be pneumatized, or even realizing that such a map would be useful?
  3. Holy crap, how have I been working on dinosaur bones — and specifically their associated soft tissues — for more than two decades without wondering exactly how the blood was getting into and out of each bone? 

Arguably, not only should Mike and I have done this project first, I should have taken a stab at it way back when I was working on my Master’s thesis. Better late than never, I guess.

I used a sauropod caudal as my vertebral archetype because it has all the bits a tetrapod vertebra can have, including the hemal arch or chevron. This was important, because Zurriaguz et al. (2017) demonstrated that the chevrons are pneumatic in some titanosaurs. 

 

For the actual presentation I redrew the vessels on top of a scan of a Camarasaurus caudal from Marsh, which Mike found and cleaned up (modified from Marsh 1896: plate 34, part 4, and plate 39, part 3c). 

We deliberately used an unfused caudal to emphasize that ‘ribs’ — technically, costal elements — are present, they just fuse to the neural arch and centrum rather than remaining separate, mobile elements like dorsal ribs.

Anyway, I’m yapping about this now because this project is rolling: Mike and I submitted an abstract on it for the 3rd Palaeontological Virtual Congress, and a short slideshow on the project is now up at the 3PVC site for attendees to look at and comment on. The congress started last Wednesday and runs through Dec. 15, after which I’m sure we’ll submit the abstract and slide deck somewhere as a preprint, and then turn it into a paper as quickly as possible.

I’ll probably have more to say on this in a day or so, but for now the comment field is open, and your thoughts are welcome.

References

 

Posted by Matt Wedel
Filed in camarasaurs, caudal, I'm stupid, pneumaticity, Things I should have posted ten years ago, Thinking it through, timely
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