Today finally sees the publication of a paper (Taylor 2022) that’s been longer in gestation than most (although, yes, all right, not as long as the Archbishop). I guess the first seeds were sown almost a full decade ago when I posted How long was the neck of Diplodocus? in May 2011, but it was submitted as a preprint in 2015. Since then it’s taken far longer than it should have done to get it across the line, and it is primarily with a feeling of relief that I see the paper now published.

Taylor (2022: figure 4). W. H. Reed’s diagram of Quarry C near Camp Carnegie on Sheep Creek, in Albany County, Wyoming. The coloured bones belong to CM 84, the holotype of Diplodocus carnegii; other bones belong to other individuals, chiefly of Brontosaurus, Camarasaurus and Stegosaurus. Modified (cropped and coloured) from Hatcher (1901: plate I). Cervical vertebrae are purple (and greatly simplified in outline by Reed), dorsals are red, the sacrum is orange, caudals are yellow, limb girdle elements are blue, and limb bones are green.

In this quarry map for the Carnegie Diplodocus, does it seem to you that the vertebrae of the neck (in purple) are drawn unconvincingly, compared with the fairly detailed drawings of the dorsals? Does that suggest that maybe Reed — who drew this diagram years after the excavation was complete — didn’t really remember how the neck was laid out? How well does the textual description of the skeleton in situ match this map? These are the kinds of questions I was asking myself as I started thinking about what has become the paper published today.

In some ways it’s a really simple paper, pretty much summarised by its title: almost all known sauropod necks are incomplete and distorted. It started out as a formalised version of three posts on this blog (How long was the neck of Diplodocus?, Measuring the elongation of vertebrae and The Field Museum’s photo-archives tumblr, featuring: airbrushing dorsals), but somewhere along the line the tale grew in the telling and it’s ended up as 35 pages of goodness. In the process of review it acquired a lot of new material, including: a discussion of how to locate the cevicodorsal junction (summary: it’s complicated); a couple of ways to numerically quantify the degree of distortion along a neck; and a brief discussion of retrodeformation (summary: it’s complicated).

Head and neck from Janensch’s (1950b: plate VI) skeletal reconstruction of Giraffatitan brancai (= “Brachiosaurusbrancai of his usage) mounted specimen based on MB.R.2181 (formerly HMN SII). The parts of the head and neck that were lost to damage are greyed out, including the first two cervicals and the neural arches and spines of all cervicals after C8. Oh, and the head.

I hope this paper will be of use, especially to people coming into the field with the same unrealistic assumptions I had back in the early 2000s. Back then, I had in mind a project to determine the thickness of intervertebral cartilage in the neck of Diplodocus by measuring the radii of curvature of the condyles and cotyles of successive vertebrae — an idea that distortion makes unrealistic. I took the DinoMorph work at face value — something that seems incredible to me knowing what know now. The paper that came out today is basically the one I wish I’d been able to read in 2000 (but updated!)

By the way, when I was fine-tooth-combing the proof PDF a few days ago, I was delighted to be reminded that I got the phrase “rigidly defined areas of doubt and uncertainty” into the paper — a reference of course, to the words of the philosopher Vroomfondel in The Hitch-Hiker’s Guide to the Galaxy. I’ll file this alongside the Monty Python reference in my history-of-sauropod-research book chapter and the Star Wars paraphrase that opens a computer-science paper I lead-authored in 2005.

References

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

 

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

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.

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

 

As I was clearing out some old documents, I stumbled on this form from 2006:

This was back when Paul Upchurch’s dissertation, then only 13 years old, contained much that still unpublished in more formal venues, notably the description of what was then “Pelorosaurusbecklesii. As a fresh young sauropod researcher I was keen to read this and other parts of what was then almost certainly the most important and comprehensive single publication about sauropods.

I remember contacting Paul directly to ask if he could send a copy, but he didn’t have it in electronic form. So I wrote (on his advice, I think) to Cambridge University Library to request a copy from them. The form is what I got back, saying sure I could have a copy — for £160.08 if I wanted a photocopy, or £337.80 for a microfilm. Since inflation in the UK has run at about 2.83% per year since 2006, that price of £160.08 back then is equivalent to about £243 in today’s money.

Needless to say, I didn’t pursue this any further (and to my shame I’m not even sure I bothered replying to say no thanks). To this day, I have never read Paul’s dissertation — though 28 years after it was completed, it’s obviously less relevant now than it was back in the day.

What is the point of this story? What information pertains?

My point isn’t really “Look how exploitative Cambridge University Library’s pricing is” — I have no experience in running a library, and no realistic sense of what it costs in staff time and materials to make a photocopy of a substantial dissertation. Perhaps the price was only covering costs.

The point instead is: look how things have changed. Newly minted Ph.Ds now routinely deposit copies of their dissertations in repositories where they can be freely read by anyone, anywhere. Here is one recent example from my own university: Logan King’s 2021 dissertation, Macroevolutionary and Ontogenetic Trends in the Anatomy and Morphology of the Non-Avian Dinosaur Endocranium.

This is important. I often think about the Library Loon’s 2012 blog-post Framing Incremental Gains. It’s easy, if you’re in open-access advocacy, to feel the burden of how ssslllooowwwlllyyy things seem to change. Sometimes I’ve heard people claim that nothing has changed in the last 30 years. I completely understand the frustration that leads people to say such things. But it’s not true. Things have changed a lot, and are still changing fast. We seem to be past the tipping point where more than half of all newly published papers are open access. There is a lot to celebrate.

Of course that’s not to deny that there’s plenty more work to be done, and plenty of other ways our present scholarly publishing infrastructure desperately needs changing. But in pushing for that, let’s not neglect how much things have improved.

Back in June, I saw a series of tweets by sculptor and digital artist Ruadhrí Brennan, showing off the work he’d been doing on sculpting brachiosaurid skulls: Giraffatitan, Brachiosaurus (based on the Felch Quarry skull USNM 5730) and Europasaurus. Impressed, I asked if he would send a Giraffatitan skull, and here it is!

Right lateral view

You can immediately see two things: one, it’s good. (I’ll have more to say about this.) And second, it’s small, It’s leaned up against a stack of smallish coins in this photo, to give me the true lateral perspective I wanted, and those coins (10p, 20p, 20p, 5p) also make a decent ad-hoc scalebar.

In fact, it’s sculpted at 1:10 scale — about 9 cm from the tip of the premaxilla to the rearmost projection of the parietals, implying about 90 cm total length for the skull MB.R.2223.1 (“t 1”) — a figure surprisingly difficult to find in the literature (can anyone help?) but consonant with how big it seems in real life.

Anterior view

At that scale, the detail is pretty amazing. Its not just that the overall proportions of the skull are so true, but the visible junctions between the bones — as for example between the paired ascending processes of the two premaxilae, as apparent in anterior view — but the texture of the bone, including things like vascular foramina for the lips but also just straight-up bone surface. It’s a lovely job.

Right anterodorsolateral view

This view is a pretty good match for what we used in the second Shedloads of Awesome post back in 2008 — in fact, let’s just put them side by side so we can compare more easily.

As you can see, I slightly muffed the photography of the model — I could do a better job of matching the aspect I tried. But we’re in the ballpark, and it’s easy to see from this angle how much the model skull really couldn’t be anything other than what it is. That said, there are a few places where it seems the bone junctions don’t quite match those of the real skull. Most obviously, in the real skull the lacrimal seems to laterally overlap the nasal dorsally and the maxilla/jugal ventrally, whereas in the model it fits in more neatly with both. But I am inclined to think this is not so much a mistake as a correction to allow for poor articulation and distortion in the original — a restoration, in other words.

Here’s a different oblique view:

Left anterodorsolateral view, from a rather more dorsal and less lateral perspective than the previous image.

The story here really is just what an odd shape this familiar skull is when viewed in this perspective, and a valuable reminder that we should all try to avoid getting too suckered in by the over-familiar lateral views of various things. 3D objects are weird. They trick you. That’s why, for example, two scapulae that look very different in photos might actually be very similar in reality: the difference is in the angle of the photograph, not in the photographed bones.

Anyway, moving on from that cautionary tale …

The key takeaway is really just that this Giraffatitan skull is very nice, and it leaves me wishing I also had the Camarsaurus one for comparison … even though camarsaurs are ugly and stupid.

Oh, what’s that you say? You want a Giraffatitan skull of your very own? Well, you can have one: get it from the Scaled Beasts shop!

FMNH P13018 with me for scale. Photo by Holly Woodward.

Some of the Burpee Museum folks and PaleoFest speakers visited the Field Museum of Natural History in Chicago after the 2020 ‘Fest. I hadn’t been there since 2012, and a lot had changed. More on that in future posts, maybe. Here I am with FMNH 13018, a right femur referred by von Huene (1929) to Argyrosaurus superbus (note, though, that Mannion and Otero 2012 considered this specimen to be Titanosauria indet., hence the hedge in the title of the post). It’s 211cm long, which is pretty darn big but still well short of the record.

Speaking of the record, here’s a list of the largest sauropod femora (as always, updates in the comments are welcome!):

  1. 250cm – Argentinosaurus huinculensis, MLP-DP 46-VIII-21-3 (estimated when complete)
  2. 238cm – Patagotitan mayorum, MPEF-3399/44
  3. 236cm – Patagotitan mayorum, MPEF-PV 3400/27
  4. 235cm – Patagotitan mayorum, MPEF-PV 3400/27
  5. 235cm – “Antarctosaurus” giganteus, MLP 26-316
  6. 214cm – Giraffatitan brancai, XV1
  7. 211cm – cf. Argyrosaurus superbus, FMNH P13018
  8. 203cm – Brachiosaurus altithorax, FMNH P25107
  9. 200cm – Ruyangosaurus giganteus, 41HIII -0002 (estimated when complete)
  10. 191cm – Dreadnoughtus schrani, MPM-PV 1156

The list is necessarily incomplete, because we have no preserved femora for Puertasaurus, Notocolossus, Futalognkosaurus, or the largest individuals of Sauroposeidon and Alamosaurus, all of which probably had femora in the 210-250cm range. For that matter, most elements of the giant Oklahoma apatosaurine are 25%-33% larger than the equivalent bones in CM 3018, which implies a femur length of 223-237cm (scaled up from the 178.5cm femur of CM 3018). I’m deliberately not dealing with Maraapunisaurus or horrifying hypothetical barosaurs here.

In any case, it’s still a prodigious bone, and well worth spending a moment with the next time you’re at the Field Musuem.

References

  • Mannion, P.D. and Otero, A., 2012. A reappraisal of the Late Cretaceous Argentinean sauropod dinosaur Argyrosaurus superbus, with a description of a new titanosaur genus. Journal of Vertebrate Paleontology, 32(3):614-638.
  • Von Huene, F. 1929. Los saurisquios y ornitisquios del Creta´ceo Argentino. Anales del Museo de La Plata 3:1–196.

Starlings are amazing

October 29, 2021

Back in May, Amy Schwartz posted a photo of a starling that shethat had ringed that morning:

Impressed by the subtlety of the coloration, I wondered what would happen if I increased the colour saturation. I did this very simply: in the free image editor GIMP, I selected the parts of the photo that were starling (omitting the human hand and the background), and using the Hue-Saturation tool I wound the saturation up to 100%. Then I did the same thing again. Here is the result, with no other editing at all:

What an extraordinary riot of colour, in a bird that we mostly think of as “basically black with dots.”

So I thought I’d try the same trick on another starling photo, this one from the All About Birds page on the European Starling. Here is the original:

And here is the result of saturating the colours — this time through three cycles.

So my question is this: can other starlings see all this colour? In their own closed starling-centric world, are they fabulously colourful? Is this something close to what is perceptually apparent to animals whose eyes are attuned to different wavelengths from ours?that

I whipped up these doodles with a handwritten list of characteristics during office hours recently, and then realized that this should be a tutorial post.
 
Most of the stuff listed in the image is pretty self-explanatory, but I want to expand a bit on the textures. Nerves are bundles of axons, bound together in sheets of connective tissue. As you follow nerves outward, from the central nervous system toward the axon targets or receptive nerve endings, they will branch and branch, again and again, down to the level of individual axons. So although the axons themselves are too small to see in a gross dissection, the collected bundles of axons inside each nerve often give nerves a striated texture. 
 
In contrast, arteries are hollow muscular tubes that carry blood, and they look like hollow muscular tubes. A weird and IMHO under-appreciated fact is that arteries can’t be nourished directly by the blood that they carry; their walls are too thick. So they have tiny vessels in and on their walls, called vasa vasorum, or “vessels of the vessels”. The vasa vasorum are hair-fine when they are visible at all, and they squiggle just like macro-scale arteries, so texturally arteries often look vaguely hairy, with fine reddish threads winding across their surfaces.
 
In practice, though, the directness of the course — or lack thereof — and branching pattern is usually enough to make the call. Basically, nerves do not have time for your crap. They are hell-bent on getting where they are going with a minimum of farting around. In contrast, arteries never travel in straight lines if they can avoid it. They’re always throwing in a saucy swoop or curve, for no other reason than because it looked fun.
 
Why haven’t I talked about veins? By rights I should, since arteries usually travel with veins, and complete neurovascular bundles — each consisting of a nerve, an artery, and a vein — are common in vertebrate bodies. But in my experience students are almost never confused about the difference between arteries and veins. But for the sake of completeness, veins tend to be dark-colored in embalmed bodies, because they don’t completely empty of blood, and they are visibly thin-walled and floppy. Because veins are thin-walled, if they do empty out they can also flatten out, and look wider than the neighboring arteries. On the other hand, it’s not unusual to see a bifurcated vein, with one branch running on either side of the corresponding artery.
 
A couple of caveats about all of the above:
  • I made the infographic specifically for med students working with embalmed tissue. The colors in particular may be different in fresh tissue, and in my experience less vibrant and therefore harder to tell apart. The other factors are much less affected by the embalming process.
  • Most of these differences break down to some extent in very small vessels and nerves. If you can track them back to larger, more proximal parent vessels or nerves, it’s easier to tell, but sometimes you run across a tiny little thread and can’t tell if it’s a tube or a wire — in which case, good luck.