Some quick backstory: lots of sauropods have long, overlapping cervical ribs, like the ones shown here in Sauroposeidon (diagram from this old post):

These long cervical ribs are ossified tendons of ventral neck muscles, presumably longus colli ventralis. We know they’re ossified tendons because of their bone histology (Klein et al. 2012), and we suspect that they’re longus colli ventralis because those tendons look the same in birds, just less ossified, as in this rhea (same specimens as these even older posts: 1, 2):

Diplodocoids have apomorphically short cervical ribs, which never extend very far past the end of their respective centra and sometimes don’t overlap at all. Still, we assume the long ventral neck muscles were there, just without long ossified tendons. Which brings me to Apatosaurus, which has cervical ribs that are anteroposteriorly short but famously massive, extending very below and/or to the sides of the cervical centra — for a truly breathtaking example see this post. Here are C3 through C7 in CM 3018, the holotype of Apatosaurus lousiae (Gilmore 1936: plate 24):

At least for me, it’s hard to resist the temptation to mentally scoot those vertebrae together into articulation, and imagine that the very swoopy-looking and maybe even down-turned cervical ribs allowed the ventral tendon bundles to wrap around the bottom of each cervical rib protuberance, something like this:

But it’s just not so, because like all 2D images, Gilmore’s plate distorts 3D reality. If you get to see the mounted skeleton in person, it’s clear that the cervical ribs are all more or less in line, and none of them are pointed at the big protuberances, which stick way out ventrolaterally.

Here I’ve drawn in the likely trajectories of the longus colli ventralis tendons. My little red pathways don’t precisely match the cervical ribs as mounted, but there’s a lot of distortion and restoration going on. For example, comparing with Gilmore’s plate we can see that the cervical ribs of C5, which point downward compared to all the others, only do that because someone forced them to — the whole anterior portion of the rib, where the shaft would actually join to the capitulum and tuberculum, is reconstructed. Even if I’m a little off, it’s clear that the cervical ribs shafts point backward, they’re all more or less in two parallel lines, and none of them point down and out toward the ventrolateral processes. The photo contains a mountain of useful morphological information that you’d never get from the lateral views.

My takeaways from all this:

  1. If a person has only seen 2D images of a specimen, and especially if those 2D images have only been orthogonal views with no obliques, their little island of knowledge is surrounded by at least a sizeable lake of ignorance, if not a small ocean.
  2. That doesn’t mean that seeing specimens in person is the only antidote — 3D models and 3D prints are extremely useful, and for specimens that are difficult to manipulate because of their size or fragility, they may be more useful than seeing or handling the specimen, at least for some questions.
  3. For Apatosaurus specifically, those ventrolateral processes cry out for explanation. They’re fairly solid knobs of bone that stick way out past the ossified tendons of the ventral-most neck muscles. That’s a super-weird — and super-expensive — place to invest a bunch of bone if you’re not using it for something fairly important, especially in a lineage that had just spent the last 80-100 million years making their necks as light as possible.
  4. Pursuant to that last point, we’re now in — ugh-ouch-shame — our 8th year of BrontoSMASH!!, with still just the one conference presentation to show for it (Taylor et al. 2015). Prolly time we got moving on that again.

References

Last time, I showed you a photo of the head and neck of the London Diplodocus and asked what was wrong. Quite a few of you got it right (including Matt when we were chatting, but I asked him not to give it away by posting a comment). The 100 SV-POW! dollars, with their cash value of $0.00, go to Orribec, who was the first to reply that the atlas (cervical 1) is upside-down.

Here is again, from the other side:

The Natural History Museum’s Carnegie Diplodocus cast, skull and anterior cervical vertebrae in left lateral view. Photograph by Mike Taylor.

I noticed this — when it seems the people putting up the skeleton did not, unless this is a deliberate joke — because I happened to be particularly tuned into atlas ribs at the time. You can see what appears a tiny rib hanging below the atlas, but no neural arch above it projecting up and back to meet the prezygapophyses of the axis (cervical 2). In fact the “cervical rib” on this left side is the neural arch of the right side, rotated 180 degrees about the axis of the neck.

Here’s how this should look, from the Carnegie Museum’s own Diplodocus:

The Carnegie Museum’s Diplodocus mount, skull and anterior cervical vertebrae in left lateral view. Photograph by Matt Lamanna.

In this picture, the atlas seems to be pretty much fused onto the axis, as seen in Gilmore (1936: figure 6) which Matt helpfully reproduced in Tutorial 36.

(Digression 1: you might think that this atlas is the real thing, since the Carnegie’s mount is the one with the real CM 84/94/307 material in it. But no: the atlas does not belong to any of those, which all lack this element. It seems to be a sculpture, but we can’t figure out what it’s based on.)

(Digression 2: you might notice that the London and Carnegie skulls are rather different. That’s because the London cast still has the original skull supplied in 1907, which is a sculpture based on CM 622 (rear) and USNM 2673 (the rest), while the Carnegie’s mount at some point had its skull replaced by a cast of CM 11161 — though no-one knows when.)

(Digression 3: the diplodocine originally catalogued as CM 662, on which the rear of the skull was based, was named as the holotype of a new species Diplodocus hayi by Holland (1924), traded to the Cleveland Museum of Natural History in 1956 where it was numbered CMNH 10670, then traded on the Houston Museum of Natural History in 1963 where istbecame HMNS 175, mounted in  Houston in 1975, remounted between 2013 and 2015, and finally moved to its own new genus Galeamopus by Tschopp et al. 2015. Yes, this stuff gets complicated.)

In fact, it’s amazing how much stuff we actually don’t know about these classic specimens, including the source of the atlas for both the Carnegie mount and the various casts — which are not the same. If only there was a single definitive publication that gathered everything that is known about these mounts. Oh well, maybe some day.

Now everyone knows that all the Carnegie Diplodocus mounts around the world were cast from the same molds, and so they all have the same altas <SCREEEECH> wait what?

The Muséum National d’Histoire Naturelle’s Carnegie Diplodocus cast, posterior part of skull and anterior cervical vertebrae in left lateral view. Photograph by Vincent Reneleau.

Here we are in Paris, and the atlas has these two honking great ribs. I have not seen these in any other Carnegie Diplodocus. I know they’re absent from the Berlin cast (thanks to Daniela Schwarz), from the Vernal re-cast (personal observation) and of course from the London cast. I would welcome observations (or even better, photos) from anyone who’s in a position to look at the Vienna, Bologna, Moscow, La Plata, Madrid or Mexico City casts.

So where did these atlas ribs come from? As with so much of this, no-one really knows. It’s especially mysterious as the Paris mount is supposed to be completely unchanged since its initial mounting. But some clue to the origin of the ribs in this mount is found in Holland (1906:249–250):

Accompanying the elements of the atlas sent to the writer for study by the kindness of Professor Osborn  [i.e. AMNH 969] are two bones, undoubtedly cervical ribs. They are both bones belonging on the right side of the centra. They are reported to have been found at the same place at which the atlas was found. The writer is inclined to think that the larger of these two bones (Fig. 20), was probably the rib of the atlas and indeed it requires but little effort to see that it might very well have served such a function, and that the smaller bone (Fig. 21) was the rib of the axis. Were the stump of the rib which remains attached to the axis in the Carnegie Museum, and which Mr. Hatcher has figured, removed, this smaller rib might take its place and would undoubtedly articulate very neatly to the facet

In case you’re too lazy to go and look at Holland’s illustrations for yourself, here they are.

The atlas rib:

The axis rib:

Holland went on:

In case the view entertained by the writer is correct, the form of the atlas and the axis with their attached ribs would be as given in the accompanying sketch (Fig. 22) rather than as given in the figure which has been published by Mr. Hatcher. Such a location of these parts has in its favor the analogy of the crocodilian skeleton.

Here is that composite atlas/axis complex:

(This arrangement with closely appressed atlas and axis ribs should ring a bell for anyone who’s looked much at croc necks, as for example in Taylor and Wedel 2013:figure 19.)

The atlas ribs on the Paris mount look a decent match for the one illustrated by Holland (1906:figure 20), so it seems a reasonable guess that they were sculpted based on that element. But that only leaves us with two more mysteries:

  1. Why do we see these atlas ribs only on the Paris cast, not in the Carnegie original or any of the other casts (that I know of)?
  2. Why does this cast have atlas ribs based on one of Holland’s elements, but not axis ribs based on the other?

Anyone?

References

 

Last Saturday I was at a wedding at Holy Trinity Brompton, a London church that is conveniently located a ten-minute stroll from the Natural History Museum. As I am currently working on a history paper concerning the Carnegie Diplodocus, I persuaded my wife, my eldest son and his fiancée to join me for a quick scoot around the “Dippy Returns” exhibition.

Here is a photo that I took:

Something is wrong here — and I don’t just mean the NHM exhibition’s stygian lighting.

Who can tell me what it is? $100 in SV-POW! Dollars(*) awaits the first person to get it right in the comments.

 


(*) Cash value: $0.00.

The largest dinosaurs had individual cells more than 30 meters long. How did such things develop? Read on! Illustration from Wedel (2012: fig. 2).

Here’s something that’s been in the works for a while: a popular article in Scientific American on stretch growth of axons in large, fast-growing animals:

Smith, Douglas H., Rodgers, Jeffrey M., Dollé, Jean-Pierre, and Wedel, Mathew J. 2022. Giraffes vs. blue whales vs. dinosaurs: contest reveals which one builds its nervous system fastest to evade predators. Scientific American, https://www.scientificamerican.com/article/giraffes-vs-blue-whales-vs-dinosaurs-contest-reveals-which-one-builds-its-nervous-system-fastest-to-evade-predators/

This one started a few years ago, when Doug Smith at the University of Pennsylvania saw my ‘long nerves in dinosaurs’ paper (Wedel 2012) and reached out to me to ask about the growth of nerve cells in giant dinosaurs. Among his many other interests in neurobiology, Doug has worked on the stretch growth of axons (Smith et al. 2001, Smith 2009, Purohit and Smith 2016).

As a reminder, the axon is the “sticky-out bit” of the neuron. In unipolar neurons like the one in the cartoon above, the axon transmits signals away from the nerve cell body or soma. Most primary sensory neurons — the ones that actually receive stimuli from the environment — are pseudounipolar, meaning that the axon extends in both directions, with the soma sitting off to the side like a teardrop on a tightrope.

Also worth noting is that almost all drawings of neurons are hilariously compressed and oversimplified. I drew that cartoon neuron, above, with a few dozen synapses. Here is an actual neuron from the cerebellum, drawn from a stained specimen by Spanish anatomist Santiago Ramón y Cajal in the late 1800s:

In my hand drawn neuron cartoon, the length of the axon is only three or four times the diameter of the soma. You have motor neurons that run from your lower back to your feet, in which the axon is 10,000 times as long as the soma is wide (~1 meter vs 0.1 millimeters). The difference is even more pronounced for primary sensory neurons, some of which run from your toe-tips to your brainstem, and which have somata as small as 0.02 millimeters across, or 1/100,000th of the length of their axons. In a 20-meter whale or sauropod, the axon of a primary sensory neuron could be 1 million times longer than the soma.

How do such ridiculously elongated cells develop? One method is stretch growth, and that’s what Doug has been studying for more than two decades now. Once an axon has found its innervation target, it’s stuck, like a grappling hook trailing a rope. As the body parts between the soma and the axon terminals grow, the axon is forced to grow in length to keep up (in the grapping hook analogy, playing out more rope). This can be done in the lab, by getting neurons to connect to two plates, and then cranking the plates apart.

How fast can axons possibly grow by stretching? For that we have to look at the maximum linear growth rates of the largest and fastest-growing mammals and dinosaurs. Doug and I and our coauthors wrote a whole article about that, and it’s short. Check it out — here’s that link again.

References

Here at SV-POW! Towers, we like to show you iconic mounted skeletons from unusual perspectives. Here’s one:

Apatosaurus louisae holotype CM 3018, mounted skeleton in the public gallery of the Carnegie Museum of Natural History: head, neck, torso and hip in right posterolateral view. Photograph by Matt Wedel, 12th March 2019 (my birthday!)

Oh, man, I love that museum. And I love that specimen. And I love the one that’s standing next to it (Diplodocus CM 82, natch.) I’ve got to find a way to get myself back out there.

That’s all: just enjoy.

Last time, we looked briefly at my new paper Almost all known sauropod necks are incomplete and distorted (Taylor 2022). As hinted at in that post, this paper had a difficult and protracted genesis. I thought it might be interesting to watch the story of a published paper through its various stages of prehistory and history. Strap in, this is a long one — but hopefully of interest, especially to people who are just coming into academia and wonder how this stuff works in practice.

Taylor (2022: Figure 9). Sequences of cervical vertebrae of extant animals, showing that articular facet shape remains similar along the column. Top. Cervical vertebrae 3–7 of a mature savannah monitor lizard, Varanus exanthematicus, in anterior view. (The cervicals of monitor lizards, unlike those of sauropods and most mammals, are procoelous, with the anterior facet being concave and the posterior convex.) Bottom. cervical vertebrae 2–5 of a mature house-cat, Felis catus, in posterior view.

It’s never easy to identify when a thing started, but I suppose the first seeds of this paper were sown back in 2004, when Matt was planning a visit to London (to meet me in person for the first time, as it happens) and we were planning out what things we might do during the museum time we had booked. The Rutland cetiosaur was on our itinerary, and I wrote to Matt:

I also wondered about trying to measure the radius of curvature of any well-preserved condyles and cotyles. Are there any established procedures for doing this? (And is the material up to it?)

The answer, of course, is “no”. But that wasn’t apparent until I saw the material. That got me started thinking about all the kinds of mechanical analyses we’d like to do with fossil necks, and about how good we would need the material to be for the results to mean anything.

Those ideas percolated for some years.

May 19, 2011: I wrote How long was the neck of Diplodocus?, in which I considered some of the ways that the neck of the Carnegie Diplodocus is not quite so well established as we tend to assume, and went on to make similar observations about the Humboldt brachiosaur Giraffatitan “S II”.

September 18, 2011: I gave a talk (co-authored with Matt) at the Lyme Regis SVPCA, entitled Sauropod necks: how much do we really know?, the first half of which had grown out of the observations in that initial blog-post. (The second half was about the problems caused by the lack of preserved intervertebral cartilage in fossilised vertebrae, and that half became our 2013 PLOS ONE paper.)

September 20, 2013: I wrote Measuring the elongation of vertebrae, in which I discussed a problem with Elongation Index (EI): that crushing of cotyles makes both their vertical height and horizontal width unreliable to use in ratio with vertebral length.

June 4, 2014: I wrote The Field Museum’s photo-archives tumblr, featuring: airbrushing dorsals. Among other photos, I noted one of presacral 6 (probably D7) of the Brachiosaurus altithorax holotype, showing that before it was “restored” into its present state, it was a mosaic of bone fragments.

October 6, 2015: I submitted to PeerJ a manuscript based on these observations and others. At the same time, I published a preprint of the submitted manuscript, and briefly blogged about it under the title My most depressing paper. I expected that the paper would quickly be published in essentially its submitted form.

In the following days, the preprint and blogpost both quickly attracted many comments pointing out complete or near-complete sauropod necks that I had missed in the manuscript’s catalogue of such necks.

October 27, 2015 (only three weeks later!): I got back three reviews which were the very definition of “tough but fair”. They were written by three researchers whose sauropod work I hugely respect and admire — Paul Barrett, Paul Upchurch and Jeff Wilson — and they graciously acknowledged the strengths of the submission as well as bringing numerous justified criticisms. It’s traditional in acknowledgements sections to say nice things about the reviewers, but really these were everything one could hope for.

(I disagreed with only two of the many critical points made: one by Paul Upchurch, which we will come to later; and Paul Barrett’s recommendation that the illustrations should use only specimens in credentialled museums. For fossils, of course, that’s right. But the paper also contains numerous photos of extant-animal vertebrae from my own collection, and that’s OK — common — even, in the extant-animal literature. A house-cat is a house-cat, and the cervicals of one are not going to be meaningfully different from those of another.)

Because it had taken the journals and the reviewers only three weeks to get detailed, helpful, constructive reviews back to me, I was now in a position to make this paper a big success story: to turn the revisions around quickly, and maybe even get an acceptance within a month of submission. The time was right: the material was still fresh in my mind so soon after the initial submission, so it should have been the work of a few evenings to revise according to the reviewers’ requests and get this thing on the road.

That’s not what happened.

Instead, for reasons I can’t begin to fathom, I became downhearted at the prospect of going back to this manuscript and dealing with all the criticisms. I want to emphasize again that this is not in any way a complaint about the reviews, which were not unduly negative. I just looked at them and felt … weary. So I let it slide for a while.

The problem is, “a while” quickly became multiple months. And by then, the material was no longer fresh in my mind, so that doing the work I should have done half a year earlier would now have been a much bigger job. I would have had to load lots of stuff back into mental RAM before I could even get started. And there was always something more appealing to do. So I left it for a full year.

The problem is, “a year” quickly became multiple years. I have no excuse for this.

And for six years, this unconsummated project has been hanging over me, draining my motivation, whispering to me every time I try to work on something else. It’s been a drag on everything I’ve tried to do in palaeo, all because I didn’t summon the energy to drive a stake through its heart back in 2015.

Learn from my mistake, folks: don’t do this.

When you get the reviews back from a submission, give yourself a week to mourn that the reviewers didn’t recognise the pristine perfection of your initial submission, then get back on the horse and do the work. Just like I didn’t.

Seriously: be better than me. (That’s certainly what I plan to do.)

Anyway …

Early 2021: I finally got my act together, and got started on the big revision. And by this point it was a big revision because not only did I have to handle all those long-postponed reviews, and all the comments on the preprint and the blog-posts from 2015. I also had to handle five more years of developments. The biggest effect this had was that I needed to completely rewrite the woefully inadequate catalogue of complete necks, which in the original preprint listed only six species. The new version lists specimens rather than species, and very many more of them. To make the list as comprehensive as possible this time …

January 27, 2021: I created my initial draft of the new list as a Google Doc, and posted Towards a catalogue of complete sauropods necks asking readers on this blog to offer corrections and additions. They did. That resulted in a lot more work as I chased down details of candidate necks in published sources and sought personal communications about others. As a result …

March 24, 2021: I posted the draft list as The catalogue of complete sauropods necks nears completion. A few more comments came in as a result, but the list was apparently approaching a steady state.

March 27, 2021: Matt dropped me a line breaking down the listed necks across a basic phylogeny of sauropods, and counting the occurrences. I thought this was interesting enough to make up a new illustration, which I posted on the blog as Analysing the distribution of complete sauropod necks and added to the in progress revised manuscript.

May 11, 2021: I was working on finding a way to measure the variation of cotyle aspect ratios along preserved necks, so I could show qualitatively that they vary more in sauropod fossils than in bones of extant amniotes. I came up with a way of calculating this, but wondered if it already existed. In my post Help me, stats people! I asked if anyone knew of it, but it seemed no-one did. (In the end, the resubmitted paper offered two versions of this metric: one additive, the other multiplicative. To the best of my knowledge, these are novel, if simple, contributions.)

June 6, 2021: In one of the original reviews, Paul Upchurch had commented that a further confounding factor in understanding neck lengths is identifying the cervicodorsal junction. I started to put together a new manuscript section on that issue, and posted my initial thoughts as What’s the difference between a cervical and dorsal vertebra?. This post, too, generated some useful feedback that made its way into the version of the section that landed up in the revised paper.

At this point, I had put together much of the new material I needed for the resubmission. So I went back to the revised draft, integrated all the new and modified material, and …

July 12 2021: I submitted the new manuscript. Because it was the best part of six years since the old version had been touched, I asked PeerJ to handle it as a new submission, and invited the handling editor to solicit reviews either from the same people who’d done the first round or from different people, as they saw fit. This time I did not also post a pre-print — I really didn’t need yet more comments coming in at this point, I just needed to get the wretched thing over the line.

September 3 2021: the editorial decision was in, based on three reviews: major revisions. sigh. Again, though, the reviewers’ criticisms were mostly legitimate, and I could sympathise with the editor’s decision. One of the reviewers of the new version — Paul Upchurch — had previously reviewed to 2015 version, but the other two were new.

Needless to say, more work was required in response to these new reviews, but it was much more tractable than the big revision had been. I added a brief discussion of retrodeformation. I wrote about how we can use phylogenetic bracketing to estimate cervical counts, and three reasons why this doesn’t work as well as we’d like. I discussed how explicit documentation of articulation and damage mitigates their misleading effects. I removed a sideswipe at the journal Science, which I have to admit was out of place. I added a discussion of different definitions of the elongation index. I clarified the prose to make it clearer that my goal was not to criticise how others had done things, but to lay out for new researchers what pitfalls they will have to deal with.

But the most fundamental issue that arose in this round of review was whether the paper should be published at all. I will quote from Paul Upchurch’s review (since it is freely available, along with all the other reviews and my responses):

I have [a] fundamental, and I fear fatal, [problem] with this paper. First, and most importantly, I think it attempts to address a problem that does not really exist. It sets up a strawman with regard to the need to tell researchers that sauropod necks are less complete than we previously thought. However, I would argue that we are well aware of these issues and that the current paper does not provide convincing evidence that there is a problem with the way we are doing things now. To be clear, I am not saying that the incompleteness of sauropod necks is not a problem – it definitely is. What I’m saying is that there is little value in a paper whose main message is to tell us what we already know and take into account.

(Let me emphasize again that this criticism came in the context of a review that was careful, detailed and in many ways positive. There was absolutely nothing malicious about it — it was just Paul’s honest opinion.)

The interesting thing about this criticism is that there was absolutely nothing I could do to remedy it. A paper criticised for lacking a phylogenetic analysis can be made acceptable to the reviewers by adding a phylogenetic analysis. But a paper criticised for not needing to exist can only stand or fall by the handling editor’s agreement with either the author or the reviewer. So all I could do was write a response in the letter than accompanied my revision:

We now come to Paul’s fundamental issue with this paper: he does not believe it is necessary. He writes “The scientific community working on these issues does not need to be reminded of the general importance of understanding the limitations on the data we use”. Here I suggest he is misled by his own unique perspective as the person who quite possibly knows more about sauropods than anyone else alive. Labouring under “The curse of knowledge”, he charitably assumes other palaeontologists are as well-read and experienced as he is — but almost no-one is. I know that I, for one, desperately needed a paper along these lines when I was new to the field.

Happily, the handling editor agreed with me — as did the other two reviewers, which surely helped: “in a time of ever more sophisticated methods, it is good to be made aware of the general imperfections of the fossil record […] I thus recommend the article for publication”. So:

November 11 2021: I submitted the revised revision, along with the response letter quoted in part above.

December 15 2021: The editor requested some more minor changes. I made some of them and pushed back on a few others, then:

December 20 2021: I submitted a third version of this second attempt at the paper.

December 28 2021 (a welcome belated Christmas present): the paper was finally accepted. From here on, it was just a matter of turning handles.

January 4 2022: The proof PDF arrived, looking lovely but riven with mistakes — some of them my own, having survived multiple rounds of revision; others introduced by the typesetting process, including some unwelcome “corrections” that created new errors.

January 13 2022: I sent back a list of 56 errors that needed correcting.

January 24 2022: The paper was published at PeerJ!

Being of a pedantic turn of mind, I went through the final typeset version to check that all the proofing errors had been fixed. Most had, of course. But one in being fixed had introduced another; another was partially corrected but is still missing an apostrophe in the final version. Small stuff.

And then I went through the “things to do when a paper comes out” checklist: posting an SV-POW! article that I had prepared in the days leading up to publication; updating the SV-POW! sidebar page for this paper; adding the new paper to my publications list (and removing the separate entry for the 2015 preprint); adding it to my univeristy’s IR; adding it to my ORCiD page (though if you omit this, it seems to figure it out on its own after a while — kudos!); and skipping LinkedIn, Mendeley, ResearchGate, Academia.edu and Facebook, none of which I do.

And with that, the quest really is at an end, barring this post and any others that might occur to me to write (I have nothing more planned at this point).

Now it’s time to get that vertebral orientation paper revised and resubmitted!

References

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

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

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

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

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

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

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

References

Matt dropped me a line midweek about the catalogue of complete sauropod necks, with some interesting thoughts. He broke down the necks as listed across a basic phylogeny of sauropods, and counted the occurrences:

Simplified phylogeny of Sauropoda, showing counts of complete and near-complete necks. Captions: C, complete and described; U, complete but undescribed; –1, missing the atlas but otherwise complete; O, other near-complete necks; T, total.

Matt and I were both surprised to see that non-neosauropods are quite well represented, both inside and outside of Mamenchisauridae — although it’s a pity that two of those ten specimens are of Jobaria, for which we have next to zero information.

Diplodocoids are surprisingly poorly represented, with essentially just one each in Dicraeosauridae and Diplodocidae that are complete. And brachiosaurids are a black hole, with absolutely no representation — see the 2015 preprint for details on how unconvincing the neck of Giraffatitan is.

But camarasaurids are crushing it, probably just by being the most abundant sauropods of all time in terms of individual specimens in museums. (Of course when we say “camarasaurids”, we just mean Camarasaurus, which is the only named sauropod currently considered to belong to Camarasauridae unless you follow Mateus and Tschopp (2013) in considering Cathetosaurus to be generically distinct. But Matt and I both suspect that Camarasaurus is way over-lumped, so we’ll see how this pans out over the next decade or two.)

It’s surprising, though, that the second and third best represented sauropods in museums, Diplodocus and Apatosaurus, are both barely represented in terms of complete necks. And while it’s encouraging to see quite a few complete and nearly-complete necks among somphospondyls, including titanosaurs,it’s disappointing that about half of them are not yet described.

References

A couple of months ago, I asked for your help in compiling a list of all known complete sauropods necks. This has gone really well, and I want to thank everyone who chipped in, and all the various authors I have contacted for details as a result.

My next step is to take the raw data in the Google spreadsheet that I have been maintaining, and write it up as prose for the paper that I am shortly going to resubmit, having first done so back in 2015. And I thought it would make sense to draft that section here on SV-POW!, so I can get any further feedback before I finalize it for the manuscript.

Young and Zhao (1972:figure 3). Mamenchisaurus hochuanensis holotype CCG V 20401 as is occurred in the field.

So here goes: any additional comments at this stage will be welcome!


Unambiguously complete necks are known from published accounts of only a few sauropod specimens. In chronological order of description, the following specimens were found with their necks complete and articulated, and have been adequately described:

  • CM 11338, a referred specimen of Camarasaurus lentus described by Gilmore (1925). This is a juvenile specimen, and thus does not fully represent the adult morphology. (McIntosh et al. 1996:76 claim that this specimen is the holotype, but this is not correct: YPM 1910 is the holotype — see below.)
  • CM 3018, the holotype of Apatosaurus louisae, described by Gilmore (1936). The neck was separated from the torso but articulated from C1–C15, though the last three cervicals were badly crushed: see below for details.
  • CCG V 20401, the Mamenchisaurus hochuanensis holotype, described by Young and Zhao (1972). Each vertebra is broken in half at mid-length, with the posterior part of each adhering to the anterior part of the its successor; and all the vertebrae are badly crushed in an oblique plane.
  • ZDM T5402, a Shunosaurus lii referred specimen, described in Chinese by Zhang (1988), with English figure captions. Figure 22 depicts the atlas. Unlike the holotype T5401, this specimen is mature.
  • BYU 9047, the Cathetosaurus lewisi holotype, described by Jensen (1988). (Jensen incorrectly gives the specimen number as BYU 974.) This specimen was redescribed, and the species referred to Camarasaurus, by McIntosh et al. (1996). Although all 12 cervicals are present, “10–12, particularly 12, have suffered such severe damage that it is impossible to restore them” (McIntosh et al. 1996:76).
  • MACN-N 15, the holotype of Amargasaurus cazaui MACN-N 15, described by Salgado and Bonaparte (1991) who desribed “22 presacral vertebrae articulated with each other and attached to the skull and sacrum, relatively complete” (Salgado & Bonaparte 1991:335, translated.
  • ZDM 0083, the holotype of Mamenchisaurus youngi, described in Chinese by Ouyang and Ye (2002) with English figure captions. Figure 14 depicts the atlas and axis.
  • MUCPv-323, the holotype of Futalognkosaurus dukei, initially described by Calvo et al. 2007a and redescribed by Calvo et al. 2007b. The neck was found in two articulated sections which fit together without needing additional vertebrae in between (Jorge O. Calvo, pers. comm., 2021).
  • SSV12001, the holotype of Xinjiangtitan shanshanesis, described by Zhang et al. (2018). The original description of this specimen by Wu et al. 2013 included only the last two cervicals, which were the only ones that had been excavated at that time.

A few additional specimens are known to have complete and articulated necks, but have not yet been described:

  • USNM 13786, a referred subadult specimen of Camarasaurus lentus recently mounted at the Smithsonian. The specimen “was almost completely buried before the sinews had allowed the bones to separate” (letter from Earl Douglass to William J. Holland, 22 August 1918), and photographs kindly supplied by Andrew Moore show that the atlas was preserved.
  • MNBH TIG3, the holotype of Jobaria tiguidensis. Sereno et al. (1999:1343) assert that this species has 12 cervicals in all and say “One articulated neck was preserved in a fully dorsiflexed, C-shaped posture”. Sereno (pers. comm., 2021) confirms that the articulated neck is MNBH TIG3
  • SMA 002, referred to Camarasaurus sp. Tschopp et al. (2016), in a description of its feet, say that this specimen “lacks only the vomers, the splenial bones, the distal end of the tail, and one terminal phalanx of the right pes. The bones are preserved in three dimensions and in almost perfect articulation”.
  • MAU-Pv-LI-595, the “La Invernada” Titanosaur. Filippi et al. (2016) give a very brief account in an abstract. Filippi, pers. comm, 2021) says that the entire preserved specimen was articulated.
  • MAU-Pv-AC-01, an unnamed titanosaur mentioned in abstracts by Calvo et al. (1997) and Coria and Salgado (1999). The specimen was found in perfect articulation from skull down to the last caudal vertebrae (Rodolfo Coria, pers. comm., 2021).

The first cervical (the atlas) in sauropods is very different in form from the other vertebrae, and small and fragile. Consequently it is easily lost. Some further specimens have necks that are complete and articulated from C2 (the axis) backwards:

  • MB.R.4886, the holotype of Dicraeosaurus hansemanni, described by Janensch (1929), has a neck that complete and well preserved from C2 to C12 (the last cervical). Janensch referred to this as “specimen m” and writes “It was found articulated from the 19th caudal vertebra to the 9th cervical vertebra inclusive. The proximal part of the neck from the 8th cervical vertebra up to the axis was bent ventrally and lay at right angles to the distal part of the neck.” (Janensch 1929:41).
  • PMU 233, the holotype of Euhelopus zdanskyi, described by Wiman (1929) as “exemplar a” and redescribed by Wilson and Upchurch (2009).
  • ZDM T5401, the subadult holoype of Shunosaurus lii, described in Chinese by Zhang et al 1984. The quarry map (Zhang et al. 1984:figure 1) suggests that the atlas is missing.
  • MCT 1487-R, informally known as “DGM Series A”, described by Powell (2003). Gomani (2005:9) summarises as “12 cervical vertebrae, except the atlas, preserved in articulation with three proximal dorsal vertebrae”.
  • GCP-CV-4229, the holotype of Spinophorosaurus nigerensis, described by Remes et al. (2009). The specimen was found in very good condition and well articulated from C2 to C13, the last cervical. The atlas seems to be missing (Remes, pers. comm., 2021.

One other sauropod is complete from the first cervical, but probably not to the last:

  • MOZ-Pv1232, the holotype of Lavocatisaurus agrioensis, described by Canudo et al. (2018). This is complete from C1-C11. Canudo’s guess is that this is complete neck (Canudo, pers. comm, 2021), but the specimen doesn’t demand that conclusion and no known eusauropod has fewer than 12 cervicals.

Other sauropod specimens have necks that are complete and articulated from further back in the cervical sequence:

  • YPM 1910, Camarasaurus lentus, a mounted specimen described by Lull (1930). The neck is complete from C2 or C3, Lull was uncertain which.
  • SMA 0004, Kaatedocus siberi, described by Tschopp and Mateus (2012). Cervicals 3-14 are preserved.
  • AODF 888 (informally “Judy”), probably referrable to Diamantinasaurus, briefly described by Poropat et al. (2019). Preserved from C3 or maybe C4. “One posterior cervical (XIII or XIV) found several metres from articulated series, but appears to slot nicely into the gap between the articulated cervical series and the unprepared thoracic section, which might include at least one additional cervical (XIV or XV)” (Poropat, pers. comm. 2021).

Several necks are probably nearly complete, but it is not possible to knew due to their not being found in articulation:

  • CM 84, the holotype of Diplodocus carnegii, described by Hatcher (1901). C2–C15 are preserved, though not all in articulation; C11 may be an intrusion: see below for details.
  • ZDM T5701, the holotype of Omeisaurus tianfuensis, described by He et al. (1988). The neck was not articulated (He et al. 1988:figure 1), and was missing “two elements or so” (He et al. 1988:120).
  • QJGPM 1001, the holotype of Qijianglong guokr, described by Xing et al. (2015). On page 8, the authors say “The axis to the 11th cervical vertebra were fully articulated in the quarry. The atlas intercentrum and the 12th–17th cervical vertebrae were closely associated with the series.”
  • MNBH TIG9, a referred specimen of Jobaria tiguidensis. Wilson (2012:103) writes that this specimen “includes a partially articulated series of 19 vertebrae starting from the axis and extending through the mid-dorsal vertebrae.”
  • MNBH TIG6, another referred specimen of Jobaria tiguidensus, which has not been mentioned in the literature. Sereno (pers. comm., 2021) says that it is “a subadult partial skeleton with excellent neck” and that “the sequence was articulated from C2–11. Most of the ribs were attached as well.”

At the time of writing, the Paleobiology Database (https://paleobiodb.org/) lists more than 270 sauropod species. The nine unambigously complete and articulated necks therefore represent only one in 30 known sauropod species.

Note. The Jobaria tiguidensis individuals previously had specimen numbers beginning MNN, but the Musee National du Niger changed its name to Musée National Boubou Hama and the specimen numbers have changed with it.

What if I told you that when Matt was in BYU collections a while ago, he stumbled across a cervical vertebra — one labelled DM/90 CVR 3+4, say — that looked like this in anterior view?

I think you would say something like “That looks like a Camarasaurus cervical, resembling as it does those illustrated in the beautiful plates of Osborn and Mook (1921)”. And then you might show me, for example, the left half of Plate LXII:

And then you might think to yourself that, within its fleshy envelope, this vertebra might have looked a bit like this, in a roughly circular neck:

Reasonable enough, right?

But when what if I then told you that in fact the vertebra was twice this wide relative to its height, and looked like this?

I’m guessing you might say “I don’t believe this is real. You must have produced it by stretching the real photo”. To which I would reply “No no, hypothetical interlocutor, the opposite is the case! I squashed the real photo — this one — to produce the more credible-seeming one at the top of the post”.

You would then demand to see proper photographic evidence, and I would respond by posting these three images (which Matt supplied from his 2019 BYU visit):

BYU specimen DM/90 CVR 3+4, cervical vertebra of ?Camarasaurus in anterior view. This is the photo from which the illustration above was extracted.

The same specimen in anteroventral view.

The same specimen in something approaching ventral view.

So what’s going on here? My first thought was that this speicmen has to have been dorsoventrally crushed — that this can’t be the true shape.

And yet … counterpoint: the processes don’t look crushed: check out the really nice 3d preservation of the neural spine metapophyses, the prezygs, the transverse processes, the nice, rounded parapophyseal rami, and even the ventral aspect of the centrum. This vertebra is actually in pretty good condition.

So is this real? Is this the vertebra more or less as it was in life? And if so, does that mean that the flesh envelope looked like this?

Look, I’m not saying it isn’t ridiculous; I’m just saying this seems to be more or less where the evidence is pointing. We’ve made a big deal about how the necks of apatosaurines were more or less triangular in cross-section, rather than round as has often been assumed; perhaps we need to start thinking about whether some camarasaur necks were squashed ovals in cross section?

Part of what’s crazy here is that this makes no mechanical sense. A cantilevered structure, such as a sauropod neck, needs to be tall rather than wide in order to attain good mechanical advantage that can take the stress imposed by the neck’s weight. A broad neck is silly: it adds mass that needs to be carried without providing high anchors for the tension members. Yet this is what we see. Evolution doesn’t always do what we would expect it to do — and it goes off the rails when sexual selection comes into play. Maybe female camarasaurus were just really into wide-necked males?

Final note: I have been playing fast and loose with the genus name Camarasaurus and the broader, vaguer term camarasaur. Matt and I have long felt (without having made any real attempt to justify this feeling) that Camarasaurus is way over-lumped, and probably contains multiple rather different animals. Maybe there is a flat-necked species in among them?

(Or maybe it’s just crushing.)