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

 

Storm Giant

March 12, 2020

No, not his new Brachiosaurus humerus — his photograph of the Chicago Brachiosaurus mount, which he cut out and cleaned up seven years ago:

This image has been on quite a journey. Since Matt published this cleaned-up photo, and furnished it under the Creative Commons Attribution (CC By) licence, it has been adopted as the lead image of Wikipedia’s Brachiosaurus page [archvied]:

Consequently (I assume) it has now become Google’s top hit for brachiosaurus skeleton:

Last Saturday, Fiona and I went to Birdland, a birds-only zoo in the Cotswolds, about an hour away from where we live. The admission price also includes “Jurassic Journey”, a walking tour of a dozen or so not-very-good dinosaur models. In an interpretive centre in this area, I found this Brachiosaurus skeletal reconstruction stencilled on the wall:

I immediately knew it was the Chicago mount due to the combination of Giraffatitan anterior dorsals and Brachiosaurus posterior dorsals; but I found it more hauntingly familiar than that. A quick hunt turned up Matt’s seven-year-old post, and when I told Matt about my discovery he filled me in on its use in Wikipedia.

So this is 99% of a good story: we’re delighted that this work is out there, and has resulted in a much better Brachiosaurus image at Birdland than the rather sad-looking Stegosaurus next to it. The only slight disappointment is that I couldn’t find any sign of credit, which they really should have included given that Matt put the image out under CC By rather than in the public domain.

But as Matt said: “Even though I didn’t get credited, I’m always chuffed to see my stuff out in the world.” So true.

 

You know the drill. For ground-level Diplodocus, go here, for Apatosaurus, go here.

In case you haven’t gotten to do this, or need a refresher, or just want a little more Apatosaurus in your life. And honestly, who doesn’t? As with the previous Diplodocus walk-around, there’s no narration, just whatever ambient sound reached the mic. Go have fun.

In a word, amazingly. After 6 days (counting public galleries last Sunday), 4300 photos, 55 videos, dozens of pages of notes, and hundreds of measurements, we’re tired, happy, and buzzing with new observations and ideas.

We caught up with some old friends. Here Mike is showing an entirely normal and healthy level of excitement about meeting CM 584, a specimen of Camarasaurus from Sheep Creek, Wyoming. You may recognize this view of these dorsals from Figure 9 in our 2013 PeerJ paper.

We spent an inordinate amount of time in the public galleries, checking out the mounted skeletons of Apatosaurus and Diplodocus (and Gilmore’s baby Cam, and the two tyrannosaurs, and, and…).

I had planned a trip to the Carnegie primarily to have another look at the Haplocanthosaurus holotypes, CM 572 and CM 879. I was also happy for the chance to photograph and measure these vertebrae, CM 36034, which I think have never been formally described or referred to Haplocanthosaurus. As far as I know, other than a brief mention in McIntosh (1981) they have not been published on at all. I’m planning on changing that in the near future, as part of the larger Haplocanthosaurus project that now bestrides my career like a colossus.

The real colossus of the trip was CM 555, which we’ve already blogged about a couple of times. Just laying out all of the vertebrae and logging serial changes was hugely useful.

Incidentally, in previous posts and some upcoming videos, we’ve referred to this specimen as Brontosaurus excelsus, because McIntosh (1981) said that it might belong to Apatosaurus excelsus. I was so busy measuring and photographing stuff that it wasn’t until Friday that I realized that McIntosh made that call because CM 555 is from the same locality as CM 563, now UWGM 15556, which was long thought to be Apatosaurus excelsus but which is now (i.e., Tschopp et al. 2015) referred to Brontosaurus parvus. So CM 555 is almost certainly B. parvus, not B. excelsus, and in comparing the specimen to Gilmore’s (1936) plates of CM 563, Mike and I thought they were a very good match.

Finding the tray of CM 555 cervical ribs was a huge moment. It added a ton of work to our to-do lists. First we had to match the ribs to their vertebrae. Most of them had field numbers, but some didn’t. Quite a few were broken and needed to be repaired – that’s what I’m doing in the above photo. Then they all had to be measured and photographed.

It’s amazing how useful it was to be able to reassociate the vertebrae with their ribs. We only did the full reassembly for c6, in part because it was the most complete and perfect of all of the vertebrae, and in part because we simply ran out of time. As Mike observed in his recent post, it was stunning how the apatosaurine identity of the specimen snapped into focus as soon as we could see a whole cervical vertebra put back together with all of its bits.

We also measured and photographed the limb bones, including the bite marks on the radius (above, in two pieces) and ulna (below, one piece). Those will of course go into the description.

And there WILL BE a description. We measured and photographed every element, shot video of many of them, and took pages and pages of notes. Describing even an incomplete sauropod skeleton is a big job, so don’t expect that paper this year, but it will be along in due course. CM 555 may not be the most complete Brontosaurus skeleton in the world, but our ambition is to make it the best-documented.

In the meantime, we hopefully left things better documented than they had been. All of the separate bits of the CM 555 vertebrae – the centra, arches, and cervicals ribs – now have the cervical numbers written on in archival ink (with permission from collections manager Amy Henrici, of course), so the next person to look at them can match them up with less faffing about.

We have people to thank. We had lunch almost every day at Sushi Fuku at 120 Oakland Avenue, just a couple of blocks down Forbes Avenue from the museum. We got to know the manager, Jeremy Gest, and his staff, who were unfailingly friendly and helpful, and who kept us running on top-notch food. So we kept going back. If you find yourself in Pittsburgh, check ’em out. Make time for a sandwich at Primanti Bros., too.

We owe a huge thanks to Calder Dudgeon, who took us up to the skylight catwalk to get the dorsal-view photos of the mounted skeletons (see this post), and especially to Dan Pickering, who moved pallets in collections using the forklift, and moved the lift around the mounted skeletons on Tuesday. Despite about a million ad hoc requests, he never lost patience with us, and in fact he found lots of little ways to help us get our observations and data faster and with less hassle.

Our biggest thanks go to collections manager Amy Henrici, who made the whole week just run smoothly for us. Whatever we needed, she’d find. If we needed something moved, or if we needed to get someplace, she’d figure out how to do it. She was always interested, always cheerful, always helpful. I usually can’t sustain that level of positivity for a whole day, much less a week. So thank you, Amy, sincerely. You have a world-class collection. We’re glad it’s in such good hands.

What’s next? We’ll be posting about stuff we saw and learned in the Carnegie Museum for a long time, probably. And we have manuscripts to get cranking on, some of which were already gestating and just needed the Carnegie visit to push to completion. As always, watch this space.

References

This is what it’s like. The lack of narration is deliberate. We have other videos, which we’ll post at other times, with lots of yap. This one is just for reference, in case later on we need to know what the ischia look like in posterior view, or how the scapulocoracoid is curved, or whatever.

The Apatosaurus louisae walk-around video will be up in the near future. And a similar thing for both skeletons from the second floor balcony. Watch this space!

Mike’s and Matt’s excellent adventure in Pittsburgh continues! Today was Day 4, and just as yesterday offered us a unique opportunity to see the mounted Dipodocus and Apatosaurus skeletons up close on a lift, so today we got to look the two mounts from directly above!

Thanks to our host Amy Henrici and to Calder Dudgeon, we were able to go up to the maintenance balconies above the dinosaur hall, and from there we were able to see this:

It was a little bit scary up there: here’s Matt’s vertical panorama photo of me. Just below the balcony I’m standing on you can see another, which is actually far below up but further back. Below that is the main balcony that overlooks the hall. And below that, the hall itself, showing Diplodocus from above:

We think this is a first: we don’t know of any published photos of mounted sauropods from above — but now, there are some. Let’s take a closer look at the torsos:

Diplodocus carnegii holotype CM 84, torso, in dorsal view, anterior to right.

Apatosaurus louisae holotype CM 3018, torso, in dorsal view, anterior to left.

You can immediately see from here that Apatosaurus is a much broader animal than Diplodocus. That much, we could have guessed. What’s more interesting is that Apatosaurus seems to be slightly broader at the shoulders than at the hips, whereas the opposite is the case in Diplodocus.

This observation left us wondering what’s known about the relative widths of the forelimb and hindlimb articulations in extant animals. What, from the modern bestiary, has hips broader than its shoulders, and what has shoulders wider than its hips? We have no idea. Does anyone know if this has been studied, or better yet summarised?

Hot news! Matt and I will be spending the week of 11th-15th March at the Carnegie Museum in Pittsburgh: the home of the world’s two most definitive sauropods!

The Carnegie Diplodocus, CM 84, is the original from which all those Diplodocus mounts around the globe were taken, and so by far the most-seen sauropod in the world — almost certainly the most-seen dinosaur of any kind.

Diplodocus carnegii mounted holotype specimen CM 84 at the Carnegie Museum, Pittsburgh. Photo by Scott Robert Anselmo, CC By-SA. From Wikimedia.

Like most dinosaur-loving Brits, I grew up with this specimen, in the form of the cast that until recently graced the central hall of the Natural History Museum in London. It defined my concept of what a sauropod is. But I’ve never seen the original before, and I am stoked about it.

Also like most Brits — and American dinophiles often find this hard to believe — I never saw an Apatosaurus skeleton, or indeed any Apatosaurus material, when I was growing up, or even for several years after I started functioning as a palaeontologist. We just don’t have the material over here, so when I saw the mounted Brontosaurus holotype at the Yale Peabody Museum in 2009, it was a big moment for me.

But now, for the first time, I am going to see the definitive apatosaurine specimen, the Apatosaurus louisae holotype CM 3018!

Apatosaurus louisae mounted holotype specimen CM 3018 at the Carnegie Museum, Pittsburgh. Photo by Tadek Kurpaski, CC By. From Wikimedia.

(And I know this is not exactly a new observation here on SV-POW!, but: check out that neck! it’s insane!)

And of course the two big, glamorous mounted sauropods are only the tip of the iceberg. The Carnegie Museum has a ton of awesome material in collection, including Hatcher’s Haplocanthosaurus specimens, the much-loved juvenile apatosaurine cervical sequence CM 555, the Barosaurus cervical sequence CM 1198, and much much more.

We are going to be drowning in sauropods!

I’ll have more to say about this trip shortly, but I just want to close today’s post by saying two things:

First: those of you familiar with the collections at the Carnegie, what are the things that Matt and I should definitely not miss? What will we kick ourselves if we come come without having seen?

And finally: a big thank you to my wife, Fiona, who is finishing up a masters in March and definitely doesn’t need me to be out of the country and unable to help for a week of that final month. She is a marvel, and is sending me anyway.

 

Click to embiggen. Trust me.

Last year about this time I wrote:

Here’s a stupid thing: roughly 2-3 times a year I go to the field or to a museum and get hundreds of SV-POW!-able photos. Then I get back to the world and catch up on all of the work that piled up while I was away. And by the time I’m done with that, whatever motivating spark I had – to get some of those photos posted and talk about the exciting things I figured out – has dissipated.

The museum I was thinking about more than any other when I wrote that is the Museum of Osteology in Oklahoma City. I don’t get there every year, but I stop in as often as possible, and I make it more years than not. And yet, looking back through the archives I see that almost all of my posts about the Museum of Osteology came in a brief flurry five years ago. Shameful!

This summer I was out in the Oklahoma panhandle for fieldwork with Anne Weil, then I had a very quick day in the collections at the OMNH in Norman, then I had to drop my son London with relatives (he stayed for an extra week) and hop a plane home. In between the kid hand-off and the drop-dead get-to-the-airport time I had exactly one spare hour, so of course I hit the museum.

IMG_0571

UPDATE: for the curious, here’s the signage for the hanging humpback whale skeleton.

The Museum of Osteology is easily one of my favorite natural history museums in the world. Like all my favorite museums, it just packed to the gills with actual natural history objects. The signage is tasteful, informative, and discreet, and there is a blessed absence of blaring videos, rotating 3D whatsits, and interactive geegaws to ruin the experience.* You can walk all the way around the big mounted skeletons with no glass in the way. The staff are friendly and helpful, and as you can see from the photos, they even provide comfortable benches for people who wish to sit and ponder the endless forms most beautiful.

That, folks, is a damn fine museum.

* To be clear, I don’t think all videos and interactive displays are evil. But they need to enhance the experience of natural history, not be a substitute for it, and that’s a distinction that seems lost on many exhibit designers.

I was taken by this conjunction of two water-adapted artiodactyls.

Here’s the hippo by itself if you want the whole skeleton.

And a rhino to round out the big African megafauna. I showed the giraffe in this old post.

Even familiar animals that you may think you know front-to-back are often presented in new and interesting ways. I adore this horse skull, which has the maxilla and mandible dissected to show the very tall, ever-growing teeth, which erupt continuously through the horse’s life until the crowns are entirely worn away.

The textures on this giraffe skull are pretty mind-blowing.

I strongly recommend zooming in and tracing out some blood vessel pathways, especially over the orbit, at the bases of the ossicones, and in the temporal fossa (below the ossicones and behind the orbit).

Bottom line, if you are interested in the natural world at all, you owe it to yourself to visit this museum. And you’ll want to go as heavy in the wallet as you can manage, because the gift shop is ridiculous and can easily eat 30-45 minutes and all your disposable income. Take it from a survivor.