As I was figuring out what I thought about the new paper on sauropod posture (Vidal et al. 2020) I found the paper uncommonly difficult to parse. And I quickly came to realise that this was not due to any failure on the authors’ part, but on the journal it was published in: Nature’s Scientific Reports.

A catalogue of pointless whining

A big part of the problem is that the journal inexplicably insists on moving important parts of the manuscript out of the main paper and into supplementary information. So for example, as I read the paper, I didn’t really know what Vidal et al. meant by describing a sacrum as wedged: did it mean non-parallel anterior and posterior articular surfaces, or just that those surfaces are not at right angles to the long axis of the sacrum? It turns out to be the former, but I only found that out by reading the supplementary information:

The term describes marked trapezoidal shape in the
centrum of a platycoelous vertebrae in lateral view or in the rims of a condyle-cotyle (procoelous or opisthocoelous) centrum type.

This crucial information is nowhere in the paper itself: you could read the whole thing and not understand what the core point of the paper is due to not understanding the key piece of terminology.

And the relegation of important material to second-class, unformatted, maybe un-reviewed supplementary information doesn’t end there, by a long way. The SI includes crucial information, and a lot of it:

  • A terminology section of which “wedged vertebrae” is just one of ten sub-sections, including a crucial discussion of different interpretation of what ONP means.
  • All the information about the actual specimens the work is based on.
  • All the meat of the methods, including how the specimens were digitized, retro-deformed and digitally separated.
  • How the missing forelimbs, so important to the posture, were interpreted.
  • How the virtual skeleton was assembled.
  • How the range of motion of the neck was assessed.
  • Comparisons of the sacra of different sauropods.

And lots more. All this stuff is essential to properly understanding the work that was done and the conclusions that were reached.

And there’s more: as well as the supplementary information, which contains six supplementary figures and three supplementary tables, there is an additonal supplementary supplementary table, which could quite reasonably have gone into the supplementary information.

In a similar vein, even within the highly compressed actual paper, the Materials and Methods are hidden away at the back, after the Results, Discussion and Conclusion — as though they are something to be ashamed of; or, at best, an unwelcome necessity that can’t quite be omitted altogether, but need not be on display.

Then we have the disappointingly small illustrations: even the “full size” version of the crucial Figure 1 (which contains both the full skeleton and callout illustrations of key bones) is only 1000×871 pixels. (That’s why the illustration of the sacrum that I pulled out of the paper for the previous post, was so inadequate.)

Compare that with, for example, the 3750×3098 Figure 1 of my own recent Xenoposeidon paper in PeerJ (Taylor 2018) — that has more than thirteen times as much visual information. And the thing is, you can bet that Vidal et al. submitted their illustration in much higher resolution that 1000×871. The journal scaled it down to that size. In 2020. That’s just crazy.

And to make things even worse, unrelated images are shoved into multi-part illustrations. Consider the ridiculousness of figure 2:

Vidal et al. (2020: figure 2). The verticalization of sauropod feeding envelopes. (A) Increased neck range of motion in Spinophorosaurus in the dorso-ventral plane, with the first dorsal vertebra as the vertex and 0° marking the ground. Poses shown: (1) maximum dorsiflexion; (2) highest vertical reach of the head (7.16 m from the ground), with the neck 90° deflected; (3) alert pose sensu Taylor Wedel and Naish13; (4) osteological neutral pose sensu Stevens14; (5) lowest vertical reach of the head (0.72 m from the ground at 0°), with the head as close to the ground without flexing the appendicular elements; (6) maximum ventriflexion. Blue indicates the arc described between maximum and minimum head heights. Grey indicates the arc described between maximum dorsiflexion and ventriflexion. (B) Bivariant plot comparing femur/humerus proportion with sacrum angle. The proportion of humerus and femur are compared as a ratio of femur maximum length/humerus maximum length. Sacrum angle measures the angle the presacral vertebral series are deflected from the caudal series by sacrum geometry in osteologically neutral pose. Measurements and taxa on Table 1. Scale = 1000 mm.

It’s perfectly clear that parts A and B of this figure have nothing to do with each other. It would be far more sensible for them to appear as two separate figures — which would allow part B enough space to convey its point much more clearly. (And would save us from a disconcertingly inflated caption).

And there are other, less important irritants. Authors’ given names not divulged, only initials. I happen to know that D. Vidal is Daniel, and that J. L. Sanz is José Luis Sanz; but I have no idea what the P in P. Mocho, the A in A. Aberasturi or the F in F. Ortega stand for. Journal names in the bibliography are abbreviated, in confusing and sometimes ludicrous ways: is there really any point in abbreviating Palaeogeography Palaeoclimatology Palaeoecology to Palaeogeogr. Palaeoclimatol. Palaeoecol?

The common theme

All of these problems — the unnatural shortening that relagates important material into supplementary information, the downplaying of methods, the tiny figures that ram unrelated illustrations into compound images, even the abbreviating of author names and journal titles — have this in common: that they are aping how Science ‘n’ Nature appear in print.

They present a sort of cargo cult: a superstitious belief that extreme space pressures (such as print journals legitimately wrestle with) are somehow an indicator of quality. The assumption that copying the form of prestigious journals will mean that the content is equally revered.

And this is simply idiotic. Scientific Reports is an open-access web-only journal that has no print edition. It has no rational reason to compress space like a print journal does. In omitting the “aniel” from “Daniel Vidal” it is saving nothing. All it’s doing is landing itself with the limitations of print journals in exchange for nothing. Nothing at all.

Why does this matter?

This squeezing of a web-based journal into a print-sized pot matters because it’s apparent that a tremendous amount of brainwork has gone into Vidal et al.’s research; but much of that is obscured by the glam-chasing presentation of Scientific Reports. It reduces a Pinter play to a soap-opera episode. The work deserved better; and so do readers.

References

 

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

 

I am not usually one for field photographs — I am not a geologist, and one bit of rock looks the same as any other to me.  I suffer from a debilitating condition that renders me unable to see fossils in the ground, and am reliant on other people to dig ’em out, clean ’em up and reposit them before I’m able to make ’em into science.

But this … this blew me away:

Spinophorosaurus nigerensis, holotype skeleton GCP-CV-4229 in situ during excavation in the region of Aderbissinat, Thirozerine Dept., Agadez Region, Republic of Niger (Remes et al. 2009:fig. 1)

Spinophorosaurus nigerensis, holotype skeleton GCP-CV-4229 in situ during excavation in the region of Aderbissinat, Thirozerine Dept., Agadez Region, Republic of Niger. (Remes et al. 2009:fig. 1)

It’s the astonishingly complete and well-preserved type specimen of a new basal sauropod, Spinophorosaurus, that came out today in a paper lead-authored by Kristian Remes, previously best known for his work on Tendaguru diplodocines (Remes 2006, 2007, 2009) and for his work on the awesome remounting of the Berlin brachiosaur.

I’m not going to write the new taxon up in detail, but here are the figures of its vertebrae:

Spinophorosaurus nigerensis GCP-CV-4229 (holotype; C, E-I) and NMB-1698-R (paratype; A, B, D). (A, B)— Mid-cervical vertebra in left lateral (A) and ventral (B) views. (C)— Last dorsal and first sacral vertebrae in left lateral view. (D)— Clavicle in cranial view. (E, F)— Proximal caudal neural spines in lateral (E) and cranial (F) views. (G)— Mid-caudal vertebra in lateral view. (H, I)— Distal caudal vertebrae in left lateral (H) and ventral (I) views. Abbreviations: pcdl, posterior centrodiapophyseal lamina; podl, postzygodiapophyseal lamina; spol, spinopostzygapophyseal lamina. Scale bars = 10 cm.  (Remes et al. 2009:fig. 3)

Spinophorosaurus nigerensis GCP-CV-4229 (holotype; C, E-I) and NMB-1698-R (paratype; A, B, D). (A, B)— Mid-cervical vertebra in left lateral (A) and ventral (B) views. (C)— Last dorsal and first sacral vertebrae in left lateral view. (D)— Clavicle in cranial view. (E, F)— Proximal caudal neural spines in lateral (E) and cranial (F) views. (G)— Mid-caudal vertebra in lateral view. (H, I)— Distal caudal vertebrae in left lateral (H) and ventral (I) views. Abbreviations: pcdl, posterior centrodiapophyseal lamina; podl, postzygodiapophyseal lamina; spol, spinopostzygapophyseal lamina. Scale bars = 10 cm. (Remes et al. 2009:fig. 3)

(It’s a shame they didn’t figure more of it, especially as the paper was in PLoS ONE which has no length limits and absolutely stellar figure production, but it would be churlish to complain.)

Finally, here is the skeletal reconstruction: as you can see, it’s a decent size for such a basal sauropod.  Note the freaky all-osteoderm tail-club.

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

A truly amazing specimen — I am looking forward to sitting down with the paper and giving it the attention it deserves.

Best of all, you can also sit down with the paper — because, like all PLoS articles, it is freely available to anyone who wants it.  Follow the link below and enjoy!  (Also available from the linked article: super-high resolution images of the figures.)

Timely Discussion From an E-mail Exchange Today

Matt Wedel: That animal is just flat badass.

Zach Miller: It has a goddamn thagomizer!!!

References

Remes, Kristian.  2006.  Revision of the Tendaguru sauropod dinosaur Tornieria africana (Fraas) and its relevance for sauropod paleobiogeography.  Journal of Vertebrate Paleontology 26(3):651-669.
Remes, Kristian.  2007.  A second Gondwanan diplodocoid dinosaur from the Upper Jurassic Tendaguru Beds of Tanzania, East Africa. Paleontology 50(3):653-667.
Remes, Kristian.  2009.  Taxonomy of Late Jurassic diplodocid sauropods from Tendaguru (Tanzania).  Fossil Record 12 (1): 23-46. doi: 10.1002/mmng.200800008
Remes, Kristian, Francisco Ortega, Ignacio Fierro, Ulrich Joger, Ralf Kosma, Jose Manuel Marin Ferrer, for the Project PALDES, for the Niger Project SNHM, Oumarou Amadou Ide, and Abdoulaye Maga.  2009.  A new basal sauropod dinosaur from the Middle Jurassic of Niger and the early evolution of Sauropoda.  PLoS ONE 4(9):e6924. doi:10.1371/journal.pone.0006924