Credit: anonymous tattoo, Grant Harding for the caption.

Update. Here is the Instagram post that Grant got this from. Unfortunately it seems to be from an account that specialises in reposting others’ work without attribution, so we don’t know where the tattoo photo originated.

Daniel Vidal et al.’s new paper in Scientific Reports (Vidal et al. 2020) has been out for a couple of days now. Dealing as it does with sauropod neck posture, it’s obviously of interest to me, and to Matt. (See our earlier relevant papers Taylor et al. 2009, Taylor and Wedel 2013 and Taylor 2014.)

Overview

To brutally over-summarise Vidal et al.’s paper, it comes down to this: they digitized the beautifully preserved and nearly complete skeleton of Spinophorosaurus, and digitally articulated the scans of the bones to make a virtual skeletal mount. In doing this, they were careful to consider the neutral pose of consecutive vertebrae in isolation, looking at only one pair at a time, so as to avoid any unconscious biases as to how the articulated column “should” look.

Then they took the resulting pose, objectively arrived at — shown above in their figure 1 — and looked to see what it told them. And as you can well see, it showed a dramatically different pose from that of the original reconstruction.

Original skeletal reconstruction of Spinophorosaurus nigerensis (Remes et al. 2009:figure 5, reversed for ease of comparison). Dimensions are based on GCP-CV-4229/NMB-1699-R, elements that are not represented are shaded. Scale bar = 1 m.

In particular, they found that as the sacrum is distinctly “wedged” (i.e. its anteroposterior length is greater ventrally than it is dorsally, giving it a functionally trapezoidal shape, shown in their figure 1A), so that the column of the torso is inclined 20 degrees dorsally relative to that of the tail. They also found lesser but still significant wedging in the last two dorsal vertebrae (figure 1B) and apparently some slight wedging in the first dorsal (figure 1C) and last cervical (figure 1D).

The upshot of all this is that their new reconstruction of Spinophorosaurus has a strongly inclined dorsal column, and consequently an strongly inclined cervical column in neutral pose.

Vidal et al. also note that all eusauropods have wedged sacra to a greater or lesser extent, and conclude that to varying degrees all eusauropods had a more inclined torso and neck than we have been used to reconstructing them with.

Response

I have to be careful about this paper, because its results flatter my preconceptions. I have always been a raised-neck advocate, and there is a temptation to leap onto any paper that reaches the same conclusion and see it as corroboration of my position.

The first thing to say is that the core observation is absolutely right, — and it’s one of those things that once it’s pointed out it’s so obvious that you wonder why you never made anything of it yourself. Yes, it’s true that sauropod sacra are wedged. It’s often difficult to see in lateral view because the ilia are usually fused to the sacral ribs, but when you see them in three dimensions it’s obvious. Occasionally you find a sacrum without its ilium, and then the wedging can hardly be missed … yet somehow, we’ve all been missing its implications for a century and a half.

Sacrum of Diplodocus AMNH 516 in left lateral and (for our purposes irrelevant) ventral views. (Osborn 1904 figure 3)

Of course this means that, other thing being equal, the tail and torso will not be parallel with each other, but will project in such a way that the angle between them, measured dorsally, is less than 180 degrees. And to be fair, Greg Paul has long been illustrating diplodocids with an upward kink to the tail, and some other palaeoartists have picked up on this — notably Scott Hartman with his very uncomfortable-looking Mamenchisaurus.

But I do have three important caveats that mean I can’t just take the conclusions of the Vidal et al. paper at face value.

1. Intervertebral cartilage

I know that we have rather banged on about this (Taylor and Wedel 2013, Taylor 2014) but it remains true that bones alone can tell us almost nothing about how vertebrae articulated. Unless we incorporate intervertebral cartilage into our models, they can only mislead us. To their credit, Vidal et al. are aware of this — though you wouldn’t know it from the actual paper, whose single mention of cartilage is in respect of a hypothesised cartilaginous suprascapula. But buried away the supplementary information is this rather despairing paragraph:

Cartilaginous Neutral Pose (CNP): the term was coined by Taylor for “the pose found when intervertebral cartilage [that separates the centra of adjacent vertebrae] is included”. Since the amount of inter-vertebral space cannot be certainly known for most fossil vertebrate taxa, true CNP will likely remain unknown for most taxa or always based on estimates.

Now this is true, so far as it goes: it’s usually impossible to know how much cartilage there was, and what shape it took, as only very unusual preservational conditions give us this information. But I don’t think that lets us out from the duty of recognising how crucial that cartilage is. It’s not enough just to say “It’s too hard to measure” and assume it didn’t exist. We need to be saying “Here are the results if we assume zero-thickness cartilage, here’s what we get if we assume cartilage thickness equal to 5% centrum length, and here’s what we get if we assume 10%”.

I really don’t think it’s good enough in 2020 to say “We know there was some intervertebral cartilage, but since we don’t know exactly how much we’re going to assume there was none at all”.

The thing about incorporating cartilage into articulating models is that we would, quite possibly, get crazy results. I refer you to the disturbing figure 4 in my 2014 paper:

Figure 4. Effect of adding cartilage to the neutral pose of the neck of Diplodocus carnegii CM 84. Images of vertebra from Hatcher (1901:plate III). At the bottom, the vertebrae are composed in a horizontal posture. Superimposed, the same vertebrae are shown inclined by the additional extension angles indicated in Table 2.

I imagine that taking cartilage into account for the Spinophorosaurus reconstruction might have given rise to equally crazy “neutral” postures. I can see why Vidal et al. might have been reluctant to open that can of worms; but the thing is, it’s a can that really needs opening.

2. Sacrum orientation

As Vidal et al.’s figure 1A clearly shows, the sacrum of Spinophorosaurus is indeed wedge-shaped, with the anterior articular surface of the first sacral forming an angle of 20 degrees relative to the posterior articular surface of the last:

But I don’t see why it follows that “the coalesced sacrum is situated so that the posterior face of the last sacral centrum is sub-vertical. This makes the presacral series to slope dorsally and the tail to be subhorizontal (Figs. 1 and 4S)”. Vidal et al. justify this with the claim by saying:

Since a subhorizontal tail has been known to be present in the majority of known sauropods[27, 28, 29], the [osteologically induced curvature] of the tail of Spinophorosaurus is therefore compatible with this condition.

But those three numbered references are to Gilmore 1932, Coombs 1975 and Bakker 1968 — three venerable papers, all over fifty years old, dating from a period long before the current understanding of sauropod posture. What’s more, each of those three was about disproving the previously widespread assumption of tail-dragging in sauropods, but the wedged sacrum of Spinophorosaurus if anything suggests the opposite posture.

So my question is, given that the dorsal and caudal portions of the vertebral column are at some specific angle to each other, how do we decide which (if either) is horizontal, and which is inclined?

Three interpretations of the wedged sacrum of Spinophorosaurus, in right lateral view. In all three, the green line represents the trajectory of the dorsal column in the torso, and the red line that of the caudal column. At the top, the tail is horizontal (as favoured by Vidal et al. 2020) resulting in an inclined torso; at the bottom, the torso is horizontal, resulting in a dorsally inclined tail; in the middle, an intermediate posture shows both the torso and the tail slightly inclined.

I am not convinced that the evidence presented by Vidal et al. persuasively favours any of these possibilities over the others. (They restore the forequarters of Spinophorosaurus with a very vertical and ventrally positioned scapula in order to enable the forefeet to reach the ground; this may be correct or it may not, but it’s by no means certain — especially as the humeri are cross-scaled from a referred specimen and the radius, ulna and manus completely unknown.)

3. Distortion

Finally, we should mention the problem of distortion. This is not really a criticism of the paper, just a warning that sacra as preserved should not be taken as gospel. I have no statistics or even systematic observations to back up this assertion, but the impression I have, from having looked closely at quite a lot of sauropod vertebra, is the sacra are perhaps more prone to distortion than most vertebrae. So, for example, the very extreme almost 30-degree wedging that Vidal et al. observed in the sacrum of the Brachiosaurus altithorax holotype FMNH PR 25107 should perhaps not be taken at face value.

Now what?

Vidal el al. are obviously onto something. Sauropod sacra are screwy, and I’m glad they have drawn attention in a systematic way to something that had only been alluded to in passing previously, and often in a way that made it seems as though the wedging they describe was unique to a few special specimens. So it’s good that this paper is out there.

But we really do need to see it as only a beginning. Some of the things I want to see:

  • Taking cartilage into account. If this results in silly postures, we need to understand why that is the case, not just pretend the problem doesn’t exist.
  • Comparison of sauropod sacra with those of other animals — most important, extant animals whose actual posture we can observe. This might be able to tell us whether wedging really has the implications for posture that we’re assuming.
  • Better justification of the claim that the torso rather than the tail was inclined.
  • An emerging consensus on sauropod shoulder articulation, since this also bears on torso orientation. (I don’t really have a position on this, but I think Matt does.)
  • The digital Spinophorosaurus model used in this study. (The paper says “The digital fossils used to build the virtual skeleton are deposited and accessioned at the Museo Paleontológico de Elche” but there is no link, I can’t easily find them on the website and they really should be published alongside the paper.)

Anyway, this is a good beginning. Onward and upward!

References

  • Bakker, Robert T. 1968. The Superiority of Dinosaurs. Discovery 3:11–22.
  • Coombs, Walter P. 1975. Sauropod habits and habitats. Palaeogeography, Palaeoclimatology, Palaeoecology 17:1-33.
  • Gilmore, Charles W. 1932. On a newly mounted skeleton of Diplodocus in the United States National Museum. Proceedings of the United States National Museum 81:1-21.
  • Hatcher, John Bell. 1901. Diplodocus (Marsh): its osteology, taxonomy, and probable habits, with a restoration of the skeleton. Memoirs of the Carnegie Museum 1:1-63.
  • Osborn, Henry F. 1904. Manus, sacrum and caudals of Sauropoda. Bulletin of the American Museum of Natural History 20:181-190.
  • Taylor, Michael P. 2014. Quantifying the effect of intervertebral cartilage on neutral posture in the necks of sauropod dinosaurs. PeerJ 2:e712. doi:10.7717/peerj.712
  • Taylor, Michael P., and Mathew J. Wedel. 2013c. The effect of intervertebral cartilage on neutral posture and range of motion in the necks of sauropod dinosaurs. PLOS ONE 8(10):e78214. 17 pages. doi:10.1371/journal.pone.0078214
  • Taylor, Michael P., Mathew J. Wedel and Darren Naish. 2009. Head and neck posture in sauropod dinosaurs inferred from extant animals. Acta Palaeontologica Polonica 54(2):213-230.
  • Vidal, Daniel, P Mocho, A. Aberasturi, J. L. Sanz and F. Ortega. 2020. High browsing skeletal adaptations in Spinophorosaurus reveal an evolutionary innovation in sauropod dinosaurs. Scientific Reports 10(6638). Indispensible supplementary information at https://static-content.springer.com/esm/art%3A10.1038%2Fs41598-020-63439-0/MediaObjects/41598_2020_63439_MOESM1_ESM.pdf
    doi:10.1038/s41598-020-63439-0

 

Heinrich Mallison sent me this amazing photo, which he found unattributed on Facebook:

Infuriatingly, I’ve not been able to track down an original source for this: searching for the text just finds a bunch of reposts on meme sites, and Google’s reverse image search just reports a bunch of hits on Reddit:

The line-drawing shows some scientific understanding of bird skeletons, so I imagine someone put real thought into this and is unhappy that the image is propagating uncredited. If that person reads this, please leave a comment: I’d love to credit it properly.

Anyway … what’s going on here?

Birds (like all vertebrates) have two tubes running down the ventral aspect of the neck (i.e. below the vertebrae): the trachea, for breathing, and the oesophagus, for swallowing. But these both open into the back of the mouth and are not piped up past it. I’ve not dissected enough bird heads to show this clearly, but when I was taking Veronica apart the trachea was pretty visibly ending in the mouth cavity, not plumbed up past the mouth into the nasal space:

So yes, I think it’s true: shoebills can bulge their spines out of their mouths.

Why? My best guess that there’s just nowhere else for the spine to go when the neck is retracted. There’s a big empty space in the mouth, why let it go to waste?

Hello, ladies!

March 28, 2019

To my shock, I find that we seem never to have posted Bob Nicholls’ beautiful sketch Hello, ladies! on SV-POW!. His recent tweet reminded me about this piece, so here it is!

Like so many classic sauropod sketches, this was executed during a mammal-tooth talk at SVPCA: this one back in 2013, the year of our first Barosarus talk. (Our second was in 2016.)

Bob’s sketch shows speculative sexual display behaviour. We have no direct evidence for (or against) such behaviour; but while we don’t believe sexual selection was the main reason for sauropods evolving long necks, it seems inevitable that long necks evolved for other purposes would be exapted for sexual display.

I always love Bob’s sketches — in fact, for most palaeoartists, I tend to like their sketches more than their finished pieces. Among the many things about this one that make me jealous is all the females in the background admiring the male: the economy of line where Bob can not only summon up a perfectly cromulent diplodocid head in a few strokes, but imbue it with a sense of being inquisitive about the display. It’s magical.

 


Whatever happened to that 2013 Barosaurus project?, you may ask.

Well, the first thing that happened is that after we submitted the abstract, entitled Barosaurus revisited: the concept of Barosaurus (Dinosauria: Sauropoda) is based on erroneously referred specimens, we realised that there was a tiny, tiny mistake in our work. So by the time I gave the talk at the actual conference, the title slide was this:

Then you will recall we did an efficient job of converting the conference presentation into a manuscript, which we submitted as a preprint less than a month after the conference. The preprint quickly garnered amazingly helpful comments, which we used to extensively revise the manuscript.

For reasons we don’t understand, there was a three-year delay before we got it submitted for peer-review in 2016; but when we did finally submit, we did it in the confident hope that it would sail through peer-review, having already been extensively reviewed and revised.

But it was not to be. When we got the reviews back, they asked for a ton of changes, and that process was just too dispiriting to face having already made a ton of changes based on the first set of comments just prior to the submission. So the tedious process got back-burnered, and the suddenly three more years passed.

The upshot is that I still need to handle the reviews on the 2nd version of the paper, and shove the blasted thing through the peer-review process. I will, to be frank, be glad to get it out of my POOP chute, so I can think about other things — not least, the 2016 Barosaurus project.

Having spent much of the last few days playing with the cervical vertebrae of a subadult apatosaur, and trying to make sense of those of the mounted adult, neck ontogeny is much on our minds. Here’s an example from the less charismatic half of Saurischia.

I was forcibly struck, when seeing a cast of Jane the juvenile Tyrannosaurus in the museum gift-shop, by how weedy its neck is:

This being the Carnegie Museum, it was with us the work of a moment to scoot across to the Cretaceous gallery and compare with the neck of an adult, CM 9380:

As you can see, the transformation of the neck is every bit as dramatic as that of the skull, as a slender animal optimised for pursuit grows into a total freakin’ monster.

Someone ought to quantify this. I’m talking to you, theropod workers! (We’ll be busy over here with sauropods.)


Here are the full, uncropped and uncorrected, versions of the photos that I extracted the above from:

This is truly a magnificent museum.

Matt and I have completed Day 2 of our excursion to the Carnegie Musuem in Pittsburgh. Day 1 was spent in the public galleries, because collections aren’t open on Sunday, but today we got into the Big Bone room.

One of our targets was CM 555, a very nice nearly complete neck (C1-C14) from a subadult apatosaurine — quite possibly Brontosaurus excelsus, which is what John McIntosh catalogued it as, though I am not yet 100% convinced it’s the same thing as YPM 1980, the holotype of that species.

We were able to lay out the full sequence on the floor, on styroforam sheets, and spend quality time just looking at it and thinking about it. I don’t just mean documenting it for later analysis, but making use of that precious time right there with the physical specimen to think through together what it’s telling us. We have a bunch of new insights, which we’ll share when we’re not completely exhausted.

Here’s Matt with the first six cervicals. C1 (the atlas) is as usual an unprepossessing lump, but then things get interesting. C2 to C6 are all unfused, so the centra and neural arches are separate.

Behind C6, the arches are fused to the centra (though the fusion lines are still apparent in C7 and C8). This is a nice example of how, in sauropods, serial position recapitulates ontogeny — one of the great confounding factors when studying isolated vertebrae.

We’ve learned a lot already from CM 555. Tomorrow will be spent with the two big mounted diplodocids (Diplodocus carnegii CM 84 and Apatosaurus louisae CM 3018). We’ll let you know how it goes. I predict: awesome.

Thanks to a comment from long-time reader Andrew Stuck, I realised he is also the tweeter @dinodadreviews, who pointed us to Xenoposeidon in a kids’ book. Now, a review on his website of Ted Rechlin‘s comic-book Jurassic has pointed me to what I think is the first depiction of the BRONTOSMASH! hypothesis in a kids’ book:

This is nice work: it captures the mass of the animals, and resists the nearly ubiquitous tendency to make their necks too slender and elegant. The necks do look rather too short here, but I think we can explain that away as perspective foreshortening.

You’d have to say, though, that it owes more than a little inspiration to the third of Brian Engh’s early sketches:

I suppose there are only a certain number of ways to draw two apatosaurs fighting.

Anyway, it’s great to see what we consider a solidly supported palaeobiological hypothesis out there influencing young hearts and minds. We should also take this as a well-deserved prod to get on with the actual paper, which after all was meant to follow hard on the heels of our 2015 SVPCA presentation.

By the way, folks: the spelling and punctuation is “BRONTOSMASH!”. Not “Brontosmash”, not “BRONTOSMASH”: all in capitals, with an exclamation mark. It’s “the BRONTOSMASH! hypothesis”.