For those following the saga of Oculudentavis (the beautiful tiny dinosaur preserved in amber that turned out to be a lizard), three more things.

Xing et al. 2020, Extended Data Fig. 2. Computed tomography scan of HPG-15-3 in palatal view, with the mandibles removed, and an isolated quadrate. a, Full palatal view. Dashed square box in a indicates the region enlarged in b [not shown]. bp, basipterygoid process; bs, basisphenoid plate; bsr, basisphenoid rostrum; ch, choana; dt, developing tooth; pt, pterygoid; pp, papillae; pmc, medial contact of the palatal processes of the premaxillae.

First, I’ve updated the timeline in Friday’s post to include several more events, kindly pointed out by commenters Pallas1773 and Ian Corfe. Check back there to better understand the increasingly confusing sequence of events.

Second, David Marjanovic provided an excellent summary of the ICZN issues in a message on the Dinosaur Mailing List. (Summary: you can’t invalidate a name by retracting the paper in which it was erected.) David knows the details of the code as well as anyone, so his analysis is well worth reading.

Finally — and annoyingly, I can’t remember who put me on to this — an interesting Chinese-language article was published two days ago about the retraction [link] [Google translation]. (Apparently the word translated “oolong” should be “mistake”.) It contains a statement from Xing Lida, lead author of the original paper, on the reason for the retraction:

The reporter found that the key to retracting the manuscript was “research progress has been made on a new specimen with a more complete preservation of the same origin discovered by the author team.” The team realized that the skull of the new specimen was very similar to HPG-15-3, but the skeleton behind the head showed a typical squamosaurus form and should be classified as squamosaurus. This indicates that HPG-15-3 is likely to belong to the squamatosaurus, which is different from the initial conclusion.

But the article goes on to note that “there are many loopholes in this withdrawal statement”. It contains some illuminating analysis from Oliver Rauhut and Per Ahlberg, including this from Rauhut: “The main problem of the paper is that the author basically preconceived that the specimen was a bird and analyzed it under this premise (this is not necessarily intentional)“. And it claims:

As early as the evening of March 19, the corresponding author of the paper said in an interview with Caixin Mail, “She recognized the questioner’s conclusion-this is more likely to be a lizard than a bird.”

And this of course was nearly three months before the same author (Jingmai O’Connor) lead-authored the preprint reasserting the avian identity of Oculudentavis.

The more I read about all this, the stranger it seems.

Update (22 August 2020)

A new paper at Zoosystema (Dubois 2020) summarises the nomenclatural situation, citing SV-POW! in passing, and concludes that the name remains nomenclaturally valid despite the retraction of the paper in which is was named — quite rightly.

References

 

Since we wrote about the putative tiny bird Oculudentavis (Xing et al. 2020) last time, things have become rather weirder. I want to discuss two things here: how we got to where we are, and what happens to the zoological name Oculudentavis khaungraae.

Xing et al. 2020, Extended Data Fig. 1. Close-up photographs of HPG-15-3. Part a, Entire skull in left lateral view. The black arrows indicate decay products from the soft tissue of the dorsal surface of the skull and the original position of skull, which drifted before the resin hardened. Scale bars, 2 mm.

First, how we got here. The timeline is a little confused but it seems to go like this:

  • 11 March: Xing et al. (2020) name Oculudentavis khaungraae, describing it as a bird. [link]
  • 11 March: In a Facebook thread on the day the paper is published, Tracey Ford claims that at least some of the authors were told at a symposium by lizard workers that their specimen was a lizard.
  • 12 March: Mickey Mortimer (very quick work!) publishes a blog-post titled “Oculudentavis is not a theropod”, making a solid argument. [link]; see also the followup post [link]
  • 13 March: Andrea Cau, working independently, publishes a blog post in Italian titled “Doubts about the dinosaurian (and avian) state of Oculudentavis” (translated), also making a solid case [link]
  • 13 March: Wang Wei et al. (the same authorship team as in the next entry) publish a detailed, technical Chinese-language article arguing that Oculudentavis is a squamate. [link] [Google translation]
  • 18 March: Li et al. (2020), in a BioRxiv preprint, formally dispute the identity of Oculudentavis, suggesting it is a squamate. [link].
  • 3 May: at the monthly meeting of the Southern California Paleontological Society, where Jingmai O’Connor gives the talk on “The evolution of dinosaurian flight and the rise of birds” she is allegedy “quite upfront about Oculudentavis being a lizard” [link]
  • 29 May: a note is added to the online version of Xing et al. 2020 stating “Editor’s Note: Readers are alerted that doubts have been expressed about the phylogenetic placement of the fossil described in this paper. We are investigating and appropriate editorial action will be taken once this matter is resolved.” [link]. (Steven Zhang later says on Facebook, “I’ve been reliably told by one of the coauthors of the Li et al. commentary piece, Nature rejected the comment from publication but then flagged up the matter as an Editor’s Note.”)
  • 14 June: O’Connor et al. (2020) (mostly the same authors as of the original description) reassert the avian identity of Oculudentavis. [link]
  • 22 July 2020: the original article (Xing et al. 2020) is retracted, with the reason given as “We, the authors, are retracting this Article to prevent inaccurate information from remaining in the literature. Although the description of Oculudentavis khaungraae remains accurate, a new unpublished specimen casts doubts upon our hypothesis regarding the phylogenetic position of HPG-15-3.” [link]

(Note: Facebook always seems very ephemeral, so here is a screenshot of the conversation in question:

I am aware that this is only hearsay, and rather vague: what symposium, what lizard workers? But I’ll leave it here as it does seem to be part of the story — judge it as you will.)

The unambiguously strange thing here is the O’Conner et al. preprint, published after O’Connor had seemingly accepted the squamate identity of Oculudentavis, but arguing for an avian identity. The O’Connor et al. rebuttal of Li et al. is pretty clear on its position, stating at the bottom of page 2:

Our parsimony-based phylogenetic analysis run using TNT placed Oculudentavis in Aves … Forcing a relationship with squamates required 10 additional steps.

But it also contains the rather extraordinary statement “Although in the future new information may prove we are incorrect in our original interpretation … this is in no way due to gross negligence” (p3).

I think we have to assume that O’Connor changed her mind between 11 March (the original publication) and 3 May (the SoCal meeting), then changed it back again by 14 June (the rebuttal of Li et al.), and finally accepted her first change of mind had been correct by 22 July (the retraction). But other interpretations are possible.

And of course the key question here lingers: why was the paper retracted, rather than merely corrected? And why does the journal say the authors retracted it, when the lead author says that the journal did it against their will?

Anyway, enough of the past. What of the future of the name Oculudentavis khaungraae?

The first thing we can all agree on is that (assuming Oculudentavis does turn out to be a squamate), the fact that the generic name misidentifies the phylogenetic position of the taxon is neither here nor there. Zoological nomenclature is full of such misnomers: they are not, and never have been, a reason to remove a name from the record.

But the retraction of the article in which the name was published is another matter. Does it mean, as some have argued, that the name is now nomenclaturally void?

I would strongly argue that no, it does not. There are several lines of reasoning.

First, the International Code of Zoological Nomenclature does not mention retractions at all — from which the simplest conclusion to draw is that it does not recognise them, and considers a paper once published to be published forever.

Second, the wording of the code pertains to the act of publication, not to ongoing status. In Article 8 (What constitutes published work), section 8.1 (Criteria to be met) says “A work must … be issued for the purpose of providing a public and permanent scientific record”. And the Oculudentavis paper certainly was issued for that purpose.

Third, the paper is still out there and always will be: even though electronic copies now bear the warning “This article was retracted on 22 July 2020”, there are thousands of copies of Nature 579 in libraries around the world. They can’t all be amended. What’s written is written. Quod scripsi, scripsi.

And this leads us to the final and most fundamental point: you can’t rewrite history: not one line. The simple and unavoidable reality is that the paper was published. That happened. A retraction can’t undo that — all it really amounts to is an expression of regret.

So the paper was published, and still is published, and the name established in it remains, and is forever tied to the type specimen HPG-15-3. If someone describes the “new unpublished specimen” referred to above, they have no choice but to use the established name Oculudentavis khaungraae: they don’t have the option of naming it (say) Oculudentosaurus instead.

At least, that’s how it seems to me. The International Commission on Zoological Nomenclature has been informally invited on Twitter to state a position, but has not responded at the time of writing — but then it’s not tweeted at all since April, so who knows what (if anything) is going on there? I heard somewhere that Oculudentavis is not being discussed on the ICZN mailing list, but I can’t remember where.

Now would be a good time for them to issue some guidance regarding retractions. And hey, ICZN? If you want to use any of my points above, feel free!

References

 

Back in March, Nature published “Hummingbird-sized dinosaur from the Cretaceous period of Myanmar” by Xing et al. (2020), which described and named a tiny putative bird that was preserved in amber from Myanmar (formerly Burma). It’s a pretty spectacular find.

Xing et al. (2020: figure 1). a, Photograph of the amber piece with skull ventrolaterally exposed. b, c, Scan (b) and drawing (c), left lateral view. d, e, Scan (d) and drawing (e), rostral view. f, g, Scan (f) and drawing (g), occipital view. h, i, Scan (h) and drawing (i), dorsal view. de, dentary; fr, frontal; hy, hyoid bone (or bones); jg, jugal; la, lacrimal; mx, maxilla; pa, parietal; pm, premaxilla; po, postorbital; qd, quadrate; sc, scleral ossicle; so, supraoccipital; sq, squamosal; th, teeth. Scale bars, 5 mm; longer scale bar below b applies to bi.

Today, though, that paper is retracted.

That’s a very rare occurrence for a palaeontology paper. And it raises a lot of questions. The retraction notice reads, in full:

We, the authors, are retracting this Article to prevent inaccurate information from remaining in the literature. Although the description of Oculudentavis khaungraae remains accurate, a new unpublished specimen casts doubts upon our hypothesis regarding the phylogenetic position of HPG-15-3.

But we constantly see papers whose phylogenetic hypotheses are overturned by new specimens. We usually deal with this by writing a new paper. Why, in this case, is there a retraction? Something smells wrong here.

And the plot thickens in Retraction Watch’s account: corresponding author Jingmai O’Connor told them:

I don’t agree with the retraction but there is no point in fighting it, so we all signed it.

I cannot say why Nature chose to retract, I cannot hypothesize on their inner machinations. […] It is also not that unusual for paleontologists to misidentify things and for new information to correct previous hypotheses. However, Nature chose not to publish the Matter’s Arising and instead retracts our paper – they must have their reasons.

This doesn’t add up. The retraction notice explictly states that the authors retracted the original paper — yet the corresponding author says that the journal did it, more or less against the authors’ will.

I don’t know what’s going on here. I agree with O’Connor that “It’s unfortunate because this way science can’t simply correct itself (as it is supposed to do)”. If, as Li et al. (2000) argue, Oculudentavis is actually a squamate (lizard), well, fine: they can publish their conclusion, and the community will arrive at a consensus as to which identification is correct. That’s how it works, right? So why the retraction?

And there’s more: what does this mean for zoological nomenclature? Is the name Oculudentavis khaungraae still nomenclaturally valid? Opinions on this seem to vary (see the Dinosaur Mailing List thread beginning with Ben Creisler’s announcement of the retraction.)

I lean to the interpretation that, since the International Code on Zoological Nomenclature does not mention retractions, it implicitly takes the position that a paper once published is published forever. On that basis, the name Oculudentavis remains valid and attached to the holoype specimen — even if that name, with its -avis suffix, proves to have been poorly chosen in pertaining to a non-bird. (After all, there is plenty of precedent for misleading names staying in place: the whale Basilosaurus is not a saurian, and the clade of “false crocodiles” Pseudosuchia includes the true crocodiles.)

This doesn’t seem to be what Springer Nature wants: in a Facebook exchange forwarded to me by a friend who I will leave anonymous unless he or she chooses to out him or herself, Henry Gee comments “The retraction means the paper is erased from the record, and this includes the name”.

I think this is simply incorrect. But I am no expert: I await comments from those more versed in the intricacies of the ICZN.

At any rate, I can’t help but suspect that something is going on here that’s not being clearly stated. Could it be to do with the fact that Myanmar amber is itself controversial, due to the human rights record of the Myanmar regime? Is it even possible that one or more or the authors of the original Oculudentavis colluded in describing it as a bird when they knew it was something else? I don’t know (and to be 100% clear, I am not accusing anyone of anything). But I do know that Nature‘s vague and possibly misleading retraction notice is not helping, and is not in the spirit of transparency that we aim to cultivate in the sciences.

I’m pretty sure we don’t yet know the full story.

References

 

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 than 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.
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    doi:10.1038/s41598-020-63439-0

 

An important paper is out today: Carpenter (2018) names Maraapunisaurus, a new genus to contain the species “Amphicoelias fragillimus, on the basis that it’s actually a rebbachisaurid rather than being closely related to the type species Amphicoelias altus.

Carpenter 2018: Figure 5. Comparison of the neural spine of Maraapunisaurus fragillimus restored as a rebbachisaurid (A), and the dorsal vertebrae of Rebbachisaurus garasbae (B), and Histriasaurus boscarollii (C). Increments on scale bars = 10 cm.

And it’s a compelling idea, as the illustration above shows. The specimen (AMNH FR 5777) has the distinctive dorsolaterally inclined lateral processes of a rebbachisaur, as implied by the inclined laminae meeting at the base of the SPOLs, and famously has the very excavated and highly laminar structure found in rebbachisaurs — hence the species name fragillimus.

Ken’s paper gives us more historical detail than we’ve ever had before on this enigmatic and controversial specimen, including extensive background to the excavations. The basics of that history will be familiar to long-time readers, but in a nutshell, E. D. Cope excavated the partial neural arch of single stupendous dorsal vertebra, very briefly described it and illustrated it (Cope 1878), and then … somehow lost it. No-one knows how or where it went missing, though Carpenter offers some informed speculation. Most likely, given the primitive stabilisation methods of the day, it simply crumbled to dust on the journey east.

Carpenter 2018: Frontispiece. E. D. Cope, the discoverer of AMNH FR 5777, drawn to scale with the specimen itself.

Cope himself referred the vertebra to his own existing sauropod genus Amphicoelias — basically because that was the only diplodocoid he’d named — and there it has stayed, more or less unchallenged ever since. Because everyone knows Amphicoelias (based on the type species A. altus) is sort of like Diplodocus(*), everyone who’s tried to reconstruct the size of the AMNH FR 5777 animal has done so by analogy with Diplodocus — including Carpenter himself in 2006, Woodruff and Foster (2014) and of course my own blog-post (Taylor 2010).

(*) Actually, it’s not; but that’s been conventional wisdom.

Ken argues, convincingly to my mind, that Woodruff and Foster (2014) were mistaken in attributing the great size of the specimen to a typo in Cope’s description, and that it really was as big as described. And he argues for a rebbachisaurid identity based on the fragility of the construction, the lamination of the neural spine, the extensive pneumaticity, the sheetlike SDL, the height of the postzygapophyses above the centrum, the dorsolateral orientation of the transverse processes, and other features of the laminae. Again, I find this persuasive (and said so in my peer-review of the manuscript).

Carpenter 2018: Figure 3. Drawing made by E.D. Cope of the holotype of Maraapunisaurus fragillimus (Cope, 1878f) with parts labeled. “Pneumatic chambers*” indicate the pneumatic cavities dorsolateral of the neural canal, a feature also seen in several rebbachisaurids. Terminology from Wilson (1999, 2011) and Wilson and others (2011).

If AMNH FR 5777 is indeed a rebbachisaur, then it can’t be a species of Amphicoelias, whose type species is not part of that clade. Accordingly, Ken gives it a new generic name in this paper, Maraapunisaurus, meaning “huge reptile” based on Maraapuni, the Southern Ute for “huge” — a name arrived at in consultation with the Southern Ute Cultural Department, Ignacio, Colorado.

How surprising is this?

On one level, not very: Amphicoelias is generally thought to be a basal diplodocoid, and Rebbachisauridae was the first major clade to diverge within Diplodocoidae. In fact, if Maraapunisaurus is basal within Rebbachisauridae, it may be only a few nodes away from where everyone previously assumed it sat.

On the other hand, a Morrison Formation rebbachisaurid would be a big deal for two reasons. First, because it would be the only known North American rebbachisaur — all the others we know are from South America, Africa and Europe. And second, because it would be, by some ten million years, the oldest known rebbachisaur — irritatingly, knocking out my own baby Xenoposeidon (Taylor 2018), but that can’t be helped.

Finally, what would this new identity mean for AMNH FR 5777’s size?

Carpenter 2018: Figure 7. Body comparisons of Maraapunisaurus as a 30.3-m-long rebbachisaurid (green) compared with previous version as a 58-m-long diplodocid (black). Lines within the silhouettes approximate the distal end of the diapophyses (i.e., top of the ribcage). Rebbachisaurid version based on Limaysaurus by Paul (2016), with outline of dorsal based on Rebbachisaurus; diplodocid version modified from Carpenter (2006).

Because dorsal vertebrae in rebbachisaurids are proportionally taller than in diplodocids, the length reconstructed from a given dorsal height is much less for rebbachisaurs: so much so that Ken brings in the new version, based on the well-represented rebbachisaur Limaysaurus tessonei, at a mere 30.3 m, only a little over half of the 58 m he previously calculated for a diplodocine version. That’s disappointing for those of us who like our sauropods stupidly huge. But the good news is, it makes virtually no difference to the height of the animal, which remains prodigious — 8 m at the hips, twice the height of a giraffe’s raised head. So not wholly contemptible.

Exciting times!

References

 

Out today: a new Turiasaurian sauropod, Mierasaurus bobyoungi, from the Early Cretaceous Cedar Mountain formation in Utah. This comes to us courtesy of a nice paper by Royo Torres et al. (2017),

Royo-Torres et al. 2017, fig. 3. The postcranial skeleton (UMNH.VP.26004) of Mierasaurus bobyoungi gen. nov, sp. nov. with the following elements: (a) middle cervical vertebra (DBGI 69 h) in right lateral view; (b) middle cervical vertebra (DBGI 69G1) in right lateral view; (c) anterior cervical vertebra (DBGI 165) in right lateral view; (d) anterior cervical vertebra (DBGI 69G2) in right lateral view; (e) atlas (DBGI 5I) in anterior view; (f) atlas (DBGI 5I) in right lateral view; (g) posterior cervical vertebra (DBGI 95) in right lateral view; (h) posterior cervical vertebra (DBGI 19 A) in right lateral view; (i) posterior cervical vertebra (DBGI 19 A) in ventral view; (j) middle cervical vertebra (DBGI 38) in right lateral view; (k) middle cervical vertebra (DBGI 38) in dorsal view; (l) middle cervical vertebra in posterior view; (m) middle cervical vertebra (DBGI 38) in left lateral view; (n) right anterior cervical rib (DBGI 5D) in medial view; (o) right anterior cervical rib (DBGI 28 A) in medial view; (p) right anterior-middle cervical rib (DBGI 95 C) in medial view; (q) right middle cervical rib (DBGI 45 F) in dorsal view; (r) right middle cervical rib (DBGI 95 A) in dorsal view; (s) left anterior cervical rib (DBGI 95B) in lateral view; (t) left middle cervical rib (DBGI 95 H) in lateral view; (u) left middle cervical rib (DBGI 95D) in dorsal view; (v) right posterior cervical rib (DBGI 10) in dorsal view. A plus sign (+) indicates a diagnostic character for Mierasaurus bobyoungi gen. et sp. nov. An asterisk (*) indicates an autapomorphy of Mierasaurus bobyoungi gen. et sp. nov. (© Fundación Conjunto Paleontológico de Teruel-Dinópolis) in Adobe Illustrator CS5 (www.adobe.com/es/products/illustrator.html).

[Because this paper is in Nature’s Scientific Reports, it inexplicably has a big chunk of manuscript chopped out of the middle, supplied separately, not formatted properly, and for all we know not peer-reviewed. This includes such minor details as the specimen numbers of the elements that make up the holotype, and the measurements. Note to self: rant about how objectively inferior Scientific Reports is to PeerJ and PLOS ONE some time.]

Anyway, this is a nice specimen represented by lots of decent material, including plenty of presacral vertebrae, which is great.

But here’s where it gets weird. Until now, Turiasauria has been an exclusively European clade. Just like Diplodocidae used to be an exclusively North American clade until Tornieria turned up, and Dicraeosauridae used to be an exclusively Gondwanan clade until Suuwassea turned out to be a dicraeosaur, and so on.

I mentioned this in an email to Matt. His initial take was:

There is a semi-tongue-in-cheek biogeography “law” that states “Everything is everywhere, and the environment selects”.

It is kinda blowing my mind that so many taxa were shared between North America, Europe, and Africa in the Late Jurassic and yet we don’t see any turiasaurs in North America until the Cretaceous. I wonder if they are there in the Morrison and just not recognized — either some of the undescribed or undiscovered northern-Morrison weirdness, or currently lumped in with Camarasaurus.

I responded “That’s one read. Another is that we’re seeing convergence on similar eco-niches within widely different clades, and our analyses are not figuring this out.”

What I mean is this: what if our “Brachiosauridae” clade is really just a collection of not-closely-related taxa in the tall-shouldered very-high-browser ecological niche? And what if our “Dicraeosauridae” clade is just a collection of short-necked grazers, with independent evolutionary origins, but all converging on morphology that suits the same lifestyle?

And that is the thought that is currently freaking me out.

Royo-Torres et al. 2107, fig. 4. The postcranial skeleton (UMNH.VP.26004) of Mierasaurus bobyoungi gen. nov, sp. nov. with the following elements: (a) anterior dorsal vertebra (DBGI 54 A) in posterior view; (b) anterior dorsal vertebra (DBGI 54 A) in anteroventral view; (c) neural arch of a middle dorsal vertebra (DBGI 37) in right anterolateral view; (d) posterior neural arch of a dorsal vertebra (DBGI 19 A) in posterior view; (e) anterior dorsal vertebra (DBGI 16) in right lateral view; (f) anterior dorsal vertebra (DBGI 16) in posterior view; (g) posterior dorsal vertebra (DBGI 16) in anterior view; (h,i) posterior dorsal vertebra (DBGI 100NA 1) in anterior view; (j,k) posterior dorsal vertebra (DBGI 100NA 1) in posterior view; (l) posterior dorsal vertebra (DBGI 100NA 1) in left lateral view; (m) middle dorsal vertebra (DBGI 11) in anterior view; (n) centrum of a posterior dorsal vertebra (DBGI 24B) in ventral view; (o) centrum of a posterior dorsal vertebra (DBGI 24B) in anterior view; (p) centrum of a posterior dorsal vertebra (DBGI 192) in ventral view; (q) anterior-middle caudal vertebra (DBGI 23B) in anterior view; (r) anterior-middle caudal vertebra (DBGI 23B) in right lateral view; (s) posterior neural arch of a posterior caudal vertebra (DBGI 48) in left lateral view; (t) posterior caudal vertebra (DBGI 21) in anterior view; (u) posterior caudal vertebra (DBGI 21) in right lateral view; (v) distal caudal vertebra (DBI 37-34-529) in right lateral view; (W) anterior caudal vertebra (DBGI 192) in posterior view. For abbreviations see supplementary information. (i), (k) and (l) were drafted by R.R.T. (© Fundación Conjunto Paleontológico de Teruel-Dinópolis) in Adobe Illustrator CS5 (www.adobe.com/es/products/illustrator.html).

When I mentioned this possibility to Matt, he shared my existential terror:

What haunts me is this: we know from mammals and extant reptiles that morphological analyses suck. Laurasian moles, African moles, and Australian moles all look the same, despite evolving from very different ancestors. Ditto wolves and thylacines, horses and litopterns, etc.

Matt reminded of a paper we’ve talked about before (Losos et al. 1998), showing that this is exactly what happens with Caribbean anole lizards. Each island has forms that live on the ground, on the trunks of trees, and on branches. Phylogenetic analyses based on morphology put all the ground-livers together, ditto for trunk-climbers, ditto for branch-climbers. But molecular analyses show that each island was colonized once and the ground, trunk, and branch forms evolved separately for each island.

What if “turiasaur”, “brachiosaur”, and “titanosaur” are the sauropod equivalents? For “Caribbean island” read “continent”; for “lizard species”, read “sauropod clade”.

Will we ever know?

Matt is hopeful that we will. He’s confident that in time, we’ll get molecular analyses of dinosaur relationships — that it’s just a matter of time and cleverness. When that happens, things could be upended bigtime.

References

 

Just got the APP new issue alert and there are three papers that I think readers of this blog will find particularly interesting:

That’s all for now, just popping in to let people know about these things.