mark-and-matt-with-the-sauropod-dinosaurs

Quick heads up: Mark Hallett and I are both at the Society of Vertebrate Paleontology meeting in Salt Lake City. Tomorrow afternoon (Friday, October 28) at 4:15 PM we’ll be signing copies of our book, The Sauropod Dinosaurs: Life in the Age of Giants. If you’d like to get a copy of the book, or to have your already-purchased copy signed, please come to the Johns Hopkins University Press booth in the exhibitor/poster area tomorrow afternoon. We’re both generally happy to sign books whenever and wherever, but if you’d like to catch us both at the same time, this is a good opportunity. We’re hoping to do another joint book signing in Los Angeles before long – more info on that when we get it arranged.

In the meantime, or if you’re not at SVP, or if you just like cool things, check out this rad claymation video of fighting apatosaurs, by YouTube user Fred the Dinosaurman. I love this. My favorite thing is that if you’re familiar with the previously-produced, static visual images of neck-fighting apatosaurs (links collected here), you’ll see a lot of those specific poses and moments recreated as transient poses in the video. This was published back in June, but I’d missed it – many thanks to Brian Engh for the heads up.

Long-time SV-POW! readers will remember that three years ago, full of enthusiasm after speaking about Barosaurus at the Edinburgh SVPCA, Matt and I got that talk written up in double-quick time and had it published as a PeerJ Preprint in less than three weeks. Very quickly, the preprint attracted substantive, helpful reviews: three within the first 24 hours, and several more in the next few days.

This was great: it gave us the opportunity to handle those review comments and get the manuscript turned around into an already-reviewed formal journal submission in less then a month from the original talk.

So of course what we did instead was: nothing. For three years.

I can’t excuse that. I can’t even explain it. It’s not as though we’ve spent those three years churning out a torrent of other awesome papers. We’ve both just been … a bit lame.

Anyway, here’s a story that will be hauntingly familiar. A month ago, full of enthusiasm after speaking about Barosaurus at the Liverpool SVPCA, Matt and I found ourselves keen to write up that talk in double-quick time. It’s an exciting tale of new specimens, reinterpretation of an important old specimen, and a neck eight times as long as that 0f a world-record giraffe.

But it would be crazy to write the new Barosaurus paper without first having dealt with the old Barosaurus paper. So now, finally, three years on, we’ve done that. Version 2 of the preprint is now available (Taylor and Wedel 2016), incorporating all the fine suggestions of the people who reviewed the first version — and with a slightly spiffed-up title. What’s more, the new version has also been submitted for formal peer-review. (In retrospect, I can’t think why we didn’t do that when we put the first preprint up.)

Taylor and Wedel 2016: Figure 3. Barosaurus lentus holotype YPM 429, vertebra R, C?15. Top row: dorsal view; middle row, left to right: posterior, right lateral and anterior views; bottom row: ventral view, from Lull (1919: plate II). Note the apparently very low, undivided neural spine at the intersection of the PRSLs and POSLs, forward-shifted neural arch, broad prezygapophyses, broad, wing-like prezygadiapophyseal laminae, and great width across the diapophyses and across the parapophyses. Abbreviations: dia, diapophysis; para, parapophysis; prz, prezygapophysis; prdl, prezygadiapophyseal lamina; spol, spinopostzygapophyseal lamina; sprl, spinoprezygapophyseal lamina. Scale bar = 500 mm.

Taylor and Wedel 2016: Figure 3. Barosaurus lentus holotype YPM 429, vertebra R, C?15. Top row: dorsal view; middle row: posterior, right lateral and anterior views; bottom row: ventral view, from Lull (1919: plate II). Note the apparently very low, undivided neural spine at the intersection of the SPRLs and SPOLs, forward-shifted neural arch, broad prezygapophyses, broad, wing-like prezygadiapophyseal laminae, and great width across the diapophyses and across the parapophyses. Abbreviations: dia, diapophysis; para, parapophysis; prz, prezygapophysis; prdl, prezygadiapophyseal lamina; spol, spinopostzygapophyseal lamina; sprl, spinoprezygapophyseal lamina. Scale bar = 500 mm.

A big part of the purpose of this post is to thank Emanuel Tschopp, Mark Robinson, Andy Farke, John Foster and Mickey Mortimer for their reviews back in 2013. I know it’s overdue, but they are at least all acknowledged in the new version of the manuscript.

Now we cross our fingers, and hope that the formally solicited reviews for the new version of the manuscript are as helpful and constructive as the reviews in that first round. Once those reviews are in, we should be able to move quickly and painlessly to a formally published version of this paper. (I know, I know — I shouldn’t offer such a hostage to fortune.)

Meanwhile, I will finally be working on handling the reviews of this other PeerJ submission, which I received back in October last year. Yes, I have been lax; but I am back in the saddle now.

References

  • Taylor, Michael P., and Mathew J. Wedel. 2016. The neck of Barosaurus: longer, wider and weirder than those of Diplodocus and other diplodocines. PeerJ PrePrints 1:e67v2 doi:10.7287/peerj.preprints.67v2

When I separated my cat’s head from its body, the first five cervical vertebrae came with it. Never one to waste perfectly good cervicals, I prepped them as well as the skull. Here they are, nicely articulated. (Click through for high resolution.) Dorsal view at the top, then right lateral (actually, slightly dorsolateral) and ventral view at the bottom.

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Or you may prefer the same image on a black background:

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For those of us used to sauropod necks, where the atlas (C1) is a tiny, fragile ring, mammal atlases look bizarre, with their grotesque over-engineering and gigantic wings.

Since I posted my preprint “Almost all known sauropod necks are incomplete and distorted” and asked in the comments for people to let me know if I missed any good necks, the candidates have been absolutely rolling in:

I will be investigating the completeness of all of these and mentioning them as appropriate when I submit the revision of this paper. (In retrospect, I should have waited a week after posting the preprint before submitting for formal review; but I was so scared of letting it brew for years, as we’re still doing with the Barosaurus preprint to our shame, that I submitted it immediately.)

So we probably have a larger number of complete or near-complete sauropod necks than the current draft of this paper suggests. But still very few in the scheme of things, and essentially none that aren’t distorted.

So I want to consider why we have such a poor fossil record of sauropod necks. All of the problems with sauropod neck preservation arise from the nature of the animals.

First, sauropods are big. This is a recipe for incompleteness of preservation. (It’s no accident that the most completely preserved specimens are of small individuals such as CM 11338, the cow-sized juvenile Camarasaurus lentus described by Gilmore, 1925). For an organism to be fossilised, the carcass has to be swiftly buried in mud, ash or some other substrate. This can happen relatively easily to small animals, such as the many finely preserved stinkin’ theropods from the Yixian Formation in China, but it’s virtually impossible with a large animal. Except in truly exceptional circumstances, sediments simply don’t get deposited quickly enough to cover a 25 meter, 20 tonne animal before it is broken apart by scavenging, decay and water transport.

Taylor 2015: Figure 5. Quarry map of Tendaguru Site S, Tanzania, showing incomplete and jumbled skeletons of Giraffatitan brancai specimens MB.R.2180 (the lectotype, formerly HMN SI) and MB.R.2181 (the paralectotype, formerly HMN SII). Anatomical identifications of SII are underlined. Elements of SI could not be identified with certainty. From Heinrich (1999: figure 16), redrawn from an original field sketch by Werner Janensch.

Taylor 2015: Figure 5. Quarry map of Tendaguru Site S, Tanzania, showing incomplete and jumbled skeletons of Giraffatitan brancai specimens MB.R.2180 (the lectotype, formerly HMN SI) and MB.R.2181 (the paralectotype, formerly HMN SII). Anatomical identifications of SII are underlined. Elements of SI could not be identified with certainty. From Heinrich (1999: figure 16), redrawn from an original field sketch by Werner Janensch.

Secondly, even when complete sauropods are preserved, or at least complete necks, distortion of the preserved cervical vertebrae is almost inevitable because of their uniquely fragile construction. As in modern birds, the cervical vertebrae were lightened by extensive pneumatisation, so that they were more air than bone, with the air-space proportion typically in the region of 60–70% and sometimes reaching as high as 89%. While this construction enabled the vertebrae to withstand great stresses for a given mass of bone, it nevertheless left them prone to crushing, shearing and torsion when removed from their protective layer of soft tissue. For large cervicals in particular, the chance of the shape surviving through taphonomy, fossilisation and subsequent deformation would be tiny.

So I think we’re basically doomed never to have a really good sauropod neck skeleton.

We’ve noted that the Taylor et al. SVPCA abstract and talk slides are up now up as part of the SVPCA 2015 PeerJ Collection, so anyone who’s interested has probably taken a look already to see what it was about. (As an aside, I am delighted to see that two more abstracts have been added to the collection since I wrote about it.)

It was my privilege to present a talk on our hypothesis that the distinctive and bizarre toblerone-shaped necks of apatosaurs were an adaptation for intraspecific combat. This talk was based on an in-progress manuscript that Matt is lead-authoring. Also on board is the third SV-POW!sketeer, the silent partner, Darren Naish; and artist/ethologist Brian Engh.

Here is our case, briefly summarised from five key slides. First, let’s take a look at what is distinctive in the morphology of apatosaur cervicals:

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Here I’m using Brontosaurus, which is among the more extreme apatosaurs, but the same features are seen developed to nearly the same extent in Apatosaurus louisae, the best-known apatosaur, and to some extent in all apatosaurs.

Now we’ll look at the four key features separately.

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First, the cervicals ribs of sauropods (and other saurischians, including birds) anchored the longus colli ventralis and flexor colli lateralis muscles — ventral muscles whose job is to pull the neck downwards. By shifting the attachments points of these muscles downwards, apatosaurs enabled them to work with improved mechanical advantage — that is, to bring more force to bear.

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Second, by redirecting the diapophyses and parapophyses ventrally, and making them much more robust than in other sauropods, apatosaurs structured their neck skeletons to better resist ventral impacts.

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Third, because the low-hanging cervical ribs created an inverted “V” shape below the centrum, they formed a protective cradle for the vulnerable soft-tissue that is otherwise exposed on the ventral aspect of the neck: trachea, oesophagus, major blood vessels. In apatosaurus, all of these would have been safely wrapped in layers of connective tissue and bubble-wrap-like pneumatic diverticula. The presence of diverticula ventral to the vertebral centrum is not speculative – most neosauropods have fossae on the ventral surfaces of their cervical centra, and apatosaurines tend to have foramina that connect to internal chambers as well (see Lovelace et al. 2007: fig. 4, which is reproduced in this post).

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Fourth, most if not all apatosaurs have distinctive ventrally directed club-like processes on the front of their cervical ribs. (It’s hard to tell with Apatosaurus ajax, because the best cervical vertebra of that species is so very reconstructed.) How did these appear in life? It’s difficult to be sure. They might have appeared as a low boss; or, as with rhinoceros horns, they might even have carried keratinous spikes.

Putting it all together, we have an animal whose neck can be brought downwards with great force; whose neck was mechanically capable of resisting impacts on its ventral aspect; whose vulnerable ventral-side soft-tissue was well protected; and which probably had prominent clubs or spikes all along the ventral aspect of the neck. And all of this was accomplished at the cost of making the neck a lot heavier than it would have been otherwise. Off the cuff, it seems likely that the cervical series alone would have massed twice as much in apatosaurines as in diplodocines of the same neck length.

Doubling the mass of the neck is a very peculiar thing for a sauropod lineage to do – by the Late Jurassic, sauropods were the leading edge of an evolutionary trend to lengthen and lighten the neck that had been running for almost 100 million years, through basal ornithodirans, basal dinosauromorphs, basal saurischians, basal sauropodomorphs, and basal sauropods. Whatever the selective pressures that led apatosaurines to evolve such robust and heavy necks, they must have been compelling.

The possibility that apatosaurs were pushing or crashing their necks ventrally in some form of combat accounts for all of the weird morphology documented above, and we know that sexual selection is powerful force that underlies a lot of bizarre structures in extant animals, and probably in extinct ornithodirans as well (see Hone et al. 2012, Hone and Naish 2013).

What form of combat, exactly? There are various possibilities, which we’ll discuss another time. But I’ll leave you with Brian Engh’s beautiful illustration of one possible form of combat: a powerful impact of one neck brought down onto the dorsal aspect of another.

ApatoNeckSmashRoughWeb

We’re aware that this proposal is necessarily somewhat speculative. But we’re just not able to see any other explanation for the distinctive apatosaur neck. Even if we’re wrong about the ventrolateral processes on the cervical ribs supporting bosses or spikes, the first three points remain true, and given how they fly in the face of sauropods’ long history of making their necks lighter, they fairly cry out for explanation. If anyone has other proposals, we’ll be happy to hear them.

References

  • Hone, D. W., Naish, D., & Cuthill, I. C. (2012). Does mutual sexual selection explain the evolution of head crests in pterosaurs and dinosaurs?. Lethaia 45(2):139-156.
  • Hone, D. W. E., & Naish, D. (2013). The ‘species recognition hypothesis’ does not explain the presence and evolution of exaggerated structures in non‐avialan dinosaurs. Journal of Zoology 290(3):172-180.
  • Lovelace, D. M., Hartman, S. A., & Wahl, W. R. (2007). Morphology of a specimen of Supersaurus (Dinosauria, Sauropoda) from the Morrison Formation of Wyoming, and a re-evaluation of diplodocid phylogeny. Arquivos do Museu Nacional, Rio de Janeiro 65(4):527-544.

Wouldn’t it be great if, after a meeting like the 2015 SVPCA, there was a published set of proceedings? A special issue of a journal, perhaps, that collected papers that emerge from the work presented there.

Of course the problem with special issues, and edited volumes in general, is that they take forever to come out. After the Dinosaurs: A Historical Perspective conference on 6 May 2008, I got my talk on the history of sauropod research written up and submitted on 7 August, just over three months later. It took another five and a half months to make it through peer-review to acceptance. And then … nothing. It sat in limbo for a year and nine months before it was finally published, because of course the book couldn’t be finalised until the slowest of the 50 or so authors, editors and reviewers had done their jobs.

Taylor (2010: fig. 4). Marsh's reconstructions of Brontosaurus. Top: first reconstruction, modified from Marsh (1883, plate I). Bottom: second reconstruction, modified from Marsh (1891, plate XVI).

Taylor (2010: fig. 4). Marsh’s reconstructions of Brontosaurus. Top: first reconstruction, modified from Marsh (1883, plate I). Bottom: second reconstruction, modified from Marsh (1891, plate XVI).

There has to be a better way, doesn’t there?

Rhetorical question, there. There is a better way, and unsurprisingly to regular readers, it’s PeerJ that has pioneered it. In PeerJ Collections, papers can be added at any time, and each one is published as it’s ready. Better still, the whole lifecycle of the paper can (if the authors wish) be visible from the collection. You can start by posting the talk abstract, then replace it with a preprint of the complete manuscript when it’s ready, and finally replace that with the published version of the paper once it’s been through peer-review.

Take a look, for example, at the collection for the 3rd International Whale Shark Conference (which by the way was held at the Georgia Aquarium, Atlanta, which has awesome whale sharks on view.)

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As you can see from the collection (at the time of writing), only one of the constituent papers — Laser photogrammetry improves size and demographic estimates for whale sharks — has actually been published so far. But a dozen other papers exist in preprint form. That means that the people who attended the conference, saw the talks and want to refer to them in their work have something to cite.

The hot news is that Mark Young and the other SVPCA 2015 organisers have arranged for PeerJ to set up an SPPC/SVPCA 2015 Collection. I think this is just marvellous — the best possible way to make a permanent record of an important event.

The collection is very new: at the time of writing, it hosts only five abstracts (one of them ours). We’re looking forward to seeing others added. Some of the abstracts (including ours) have the slides of the talk attached as supplementary information.

talk-title-page

Although I’m lead author on the talk (because I prepared the slides and delivered the presentation), this project is really Matt’s baby. There is a Wedel et al. manuscript in prep already, so we hope that within a month or two we’ll be able to replace the abstract with a complete manuscript. Then of course we’ll put it through peer-review.

I hope plenty of other SVPCA 2015 speakers will do the same. Even those who, for whatever reason, don’t want to publish their work in PeerJ, can use the collection as a home for their abstracts and preprints, then go off and submit the final manuscript elsewhere.

As we’ve previously noted more than once here at SV-POW!, apatosaurine cervicals really are the craziest things. For one thing, they are the only dinosaur bones to have inspired the design of a Star Wars spaceship.

One result of this very distinctive cervical shape, with the ribs hanging down far below the centra, was that the necks of apatosaurines would have been triangular in cross-section, rather than tubular as often depicted. (The Apatosaurus maquette that Matt reviewed gets this right.)

Here’s how I conveyed this in two slides of my SVPCA talk:

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Although apatosaurs take this to the extreme, the same was essentially true of all sauropod necks. The ventrolateral position of the cervical ribs would have lent the necks a rounded triangular shape, or diamond-shaped in the case of less extreme sauropods whose neck soft-tissue hung below the cervical ribs.

(Previously: Sauropods were tacos, not corn dogs; and Sauropods were corn-on-the-cob, not shish kebabs.)