September 14, 2015
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:
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.
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.
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.
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).
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.
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.
- 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.
December 20, 2012
A couple of days ago, a paper by Tschopp and Mateus (2012) described and named a new diplodocine from the Morrison Formation, Kaatedocus siberi, based on a beautifully preserved specimen consisting of a complete skull and the first fourteen cervical vertebrae.
Unfortunately, the authors chose to publish their work in the Journal of Systematic Palaeontology, a paywalled journal, which means that most of you reading this will be unable to read the actual paper — at least, not unless you care enough to pay £27 for the privilege.
So you’ll just have to take my word for it when I tell you that it’s a fine, detailed piece of work, weighing in at 36 pages. It features lavish illustrations of the skull, but we won’t trouble you with those. The vertebrae are illustrated rather less comprehensively, though still better than in most papers:
It should be immediately apparent from these lateral views that the vertebra are rather Diplodocus-like. But the hot news is that there is a great raft of free supplementary information, including full five-orthogonal-view photos of all fourteen vertebrae!
Here is just one of them, C6, in glorious high resolution (click through for the full awesome):
Now, folks, that is how to illustrate a sauropod in 2012! The goal of a good descriptive paper is to be the closest thing possible to a proxy for the specimen itself, and you just can’t do that if you don’t illustrate every element from multiple directions. By getting this so spectacularly right, Tschopp and Matteus have made their paper the best illustrated sauropod descriptions for 91 years. (Yes, I am talking about Osborn and Mook 1921.)
It’s just a shame that all the awe-inspiring illustrations are tucked away in supplementary information rather than in the paper itself. Had the paper been published in a PLOS journal, for example, all the goodness could have been in one place, and it would all have been open access.
Is Kaatedocus valid?
There’s a bit of a fashion these days for drive-by synonymisation of dinosaurs, and sure enough no sooner had Brian Switek written about Kaatedocus for his new National Geographic blog than comments started cropping up arguing (or in some cases just stating) that Kaatedocus is merely Barosaurus.
It’s not. I spent a lot of time with true Barosaurus cervicals at Yale this summer, and those of Kaatedocus are nothing like them. Here is Tschopp and Mateus’s supplementary figure of C14:
And here is a posterior vertebra — possibly also C14 — of the Barosaurus holotype YPM 429, in dorsal and right lateral views:
Even allowing for a certain amount of post-mortem distortion and “creative” restoration, it should be immediately apparent that (A) Barosaurus is much weirder than most people realise, and (B) Kaatedocus ain’t it.
There may be more of a case to be made that Kaatedocus is Diplodocus — but that’s the point: it there’s a case, then it needs to be actually made, which means a point-by-point response to the diagnostic characters proposed by the authors in their careful, detailed study based on months of work with the actual specimens.
There seems to be an idea abroad at the moment that it’s somehow more conservative or sober or scientific to assume everything is a ontogenomorph of everything else — possibly catalysed by the Horner lab’s ongoing “Toroceratops” initiative and subsequent cavalier treatment of Morrison sauropods — maybe even by the Amphidocobrontowaassea paper. Folks, there is no intrinsic merit in assuming less diversity. Historically, the Victorian sauropod palaeontologists of England did at least as much taxonomic damage by assumptions of synonymy (everything’s Cetiosaurus or Ornithopsis — whatever that is) as they did by raising new taxa. The thing to do is find the hypothesis best supported by evidence, not presupposing that either splitting or lumping is a priori the more virtuous course.
Morrison sauropod diversity
As we’ve pointed out a few times in our published work, sauropod diversity in the Kimmeridgian-Tithonian in general, and in the Morrison Formation in particular, was off-the-scale crazy. There’s good evidence for at least a dozen sauropod genera in the Morrison, and more than fifteen species. Kaatedocus extends this record yet further, giving us a picture of an amazing ecosystem positively abundant with numerous species of giant animals bigger than anything alive on land today.
Sometimes you’ll hear people use this observation as a working-backwards piece of evidence that Morrison sauropods are oversplit. Nuh-uh. We have to assess taxonomy on its own grounds, then see what it tells us about ecosystem. As Dave Hone’s new paper affirms (among many others), Mesozoic ecosystem were not like modern ones. We have to resist the insidious temptation to assume that what we would have seen in the Late Jurassic is somehow analogous to what we see today on the Serengeti.
Hutton’s (or Lyell’s) idea that “the present is the key to the past” may be helpful in geology. But despite its roots as a branch of the discipline, the palaeontology we do today is not geology. When we’re thinking about ancient ecosystems, we’re talking about palaeobiology, and in that field the idea that the present is the key to the past is at best unhelpful, at worst positively misleading.
But isn’t the Kaatedocus holotype privately owned?
You’ve had two sermons already, I’m sure we can all agree that’s plenty for one blog post. I will return to this subject in a subsequent post.
Sermon doesn’t even get started.
Tschopp, Emanuel, and Octávio Mateus. 2012. The skull and neck of a new flagellicaudatan sauropod from the Morrison Formation and its implication for the evolution and ontogeny of diplodocid dinosaurs. Journal of Systematic Palaeontology. doi:10.1080/14772019.2012.746589
May 16, 2011
Thanks to everyone who joined in the discussion last time on why sauropods had such long necks. I’ve discussed this a little with Matt, and we are both amazed that so many different hypotheses have been advanced (even if some of them are tongue-in-cheek). We’ll probably come back to all these ideas later.
But today, we want to draw your attention to a new contribution to this discussion — a paper in the Journal of Zoology, with the tell-it-like-it-is title “The long necks of sauropods did not evolve primarily through sexual selection”, written by the three of us SV-POW!er rangers together with our buddy Dave “Archosaur Musings” Hone (Taylor et al. 2011).
This is one of those papers that has been literally years in the making, which is why it’s a rather belated response to the paper that we were responding to — Phil Senter’s (2006) argument that sexual selection was the primary driver of neck elongation in sauropods.
Senter supported his hypothesis by laying out six predictions which he argued should be true for sexually selected necks; then showing that, while the first two could not be assessed, the last four all supported sexual selection. In our paper, we do three things. First, we make the point that sexual selection and feeding advantage are not mutually exclusive. Second, we revisit all six predictions and show that they do not in fact support sexual selection — in fact, most of them provide support for feeding advantage. Finally, we show that no tetrapod clade comparable with Sauropoda has consistently selected for a single sexual signal.
My email records show that Darren, Matt and I were discussing this as early as 22 September 2006, just six weeks after Senter’s paper was published, and that we started working on a response only a couple of days later. But as so often happens, it got crowded out by a hundred other things. Then in November 2007 Dave Hone mentioned that he was independently thinking of writing a response, and we decided to join forces. And then … we all went back to working on other things again, touching on the necks-for-sex issue every now and then. It’s mostly due to Dave’s repeated prods that this project wasn’t allowed to wither away, and has now, finally, made it across the finish line.
Like the neck-posture paper (Taylor et al. 2009), this was a true collaboration — one of those where, for many parts of the text, none of us is sure which of us originally wrote it. It went through the wringer many times before reaching its final form, and most of the text must have been rewritten two or three times along the way. We hope all the shuffling and polishing has resulted in a paper that reads straightforwardly and even seems obvious. “When something can be read without effort, great effort has gone into its writing” — Enrique Jardiel Poncela. That’s the goal, anyway.
The paper itself is available at the link below, so take a look and see whether you find our argument convincing. As always, comments are open!
Update (the next morning)
Co-author Dave Hone discusses this paper on his own blog.
- Senter, Phil. 2006. Necks for sex: sexual selection as an explanation for sauropod dinosaur neck elongation. Journal of Zoology 271(1):45-53. doi:10.1111/j.1469-7998.2006.00197.x
- 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): 213-220.
- Taylor, Michael P., David W. E. Hone, Mathew J. Wedel and Darren Naish. 2011. The long necks of sauropods did not evolve primarily through sexual selection. Journal of Zoology, Early View (Online Version of Record published before inclusion in an issue). doi: 10.1111/j.1469-7998.2011.00824.x
April 21, 2011
[This is a guest post by frequent commenter Heinrich Mallison. Heinrich is maybe best known to SV-POW! readers for his work on digital modelling of sauropodomorphs, though that may change now that his paper on sauropod rearing mechanics is out. Read on …]
Maybe this post should have been titled “How sauropods breathed, ate, and farted”. Or maybe not. But breathing, eating and fermenting the food will play an important role.
Last week held a special pleasure for me. I spent it in New York, digitizing sauropods bones in the American Museum of Natural History’s Big Bone Room. Treasure trove that this room is, the museum still held something even better: the opening of a new special exhibit titled The World’s Largest Dinosaurs. While all such exhibits are of general interest to me, this one is special. Mark Norell, famous palaeontologist and curator at the AMNH, had a co-curator for this exhibit, Martin Sander of Bonn University, who is the head and speaker of the German Research Foundation Research Unit FOR 533 “Sauropod Biology”. As a member of FOR 533, and having received funding for both my PhD work and my first post-doc project, I am obviously somewhat biased, so please take this into account when you read this report.
The exhibition does not show a large amount of sauropods material. Not that it wouldn’t make for a nice exhibit, as the AMNH’s Hall of Saurischian Dinosaurs doesn’t really have that many sauropods (one Apatosaurus mount, to be exact, with a mashed up Barosaurus vertebral column half-hidden away and a wonderful but obviously depressed “prosauropod”, my old friend Plateosaurus, thrown in to make up a bit for the many, many stinkin’ theropod specimens). But instead of showcasing some of the usually hidden-away bones of the AMNH collection (and believe me, there is some wonderful stuff there), it rather focuses on those parts of the animal that are usually missing: the soft tissues. “How did sauropods get so big?”, or, reversing the question: “Why did and does no other group of terrestrial vertebrates reach such gigantic body sizes?” These were the questions our research group has been busily investigating for the last six years, and the answers to these question are what the exhibit now tries to communicate to the public. And it does so quite successfully!
The centrepiece is a full-sized, fleshed out model of a sauropod (Mamenchisaurus hochuanensis), but on one side the skin and superficial musculature has been cut away. The visitor can see the neck vertebrae, the trachea, the carotid artery, and the ribcage. And the ribcage is also a projection area, on which a video is played that shows the internal organs and how they work.
With a voice-over that explains the actions in simple terms, the principle of the avian-style unidirectional lung and the air sacs is explained (albeit with a small error, as lung physiologist and FOR 533 member Steve Perry was quick to point out – the AMNH has promised to fix things), as well as the basic principles of sauropod reproduction (high number of offspring). Many things are not said or shown here, which is a good thing as it allows for the normal short attention span of the average museum visitor for one piece of exhibit. Instead, interesting stuff like how much fodder a sauropod needed per day (or even per hour), a comparison of a sauropod’s and an elephant’s heart, and of a giraffe’s and a sauropod’s neck vertebra (wow, how light the sauropod one is!) are explored at small science stations spread around the room. I won’t go into a detailed description here, you can find that elsewhere on the web. The AMNH did a blogger’s preview a while ago, and invited the press for a press conference and walk-through of the exhibit with the chance to interview the scientists present on Wednesday, so much info has already been plastered all over the web. Instead, I’ll just show you some pics and talk a bit about the concept of the exhibition, and how various issues were handled that can make or break a show.
One thing is how to catch the attention of visitors and direct it to the content of the exhibit. You don’t want people just going “aw, sh*t! That is one HUGE bone/animal!” and wandering off into the next room. If you want to educate them (and that, may I remind you, is the central purpose of a museum exhibit), you need to get them interested in stuff. Get them to read texts, look at stuff (not just let their eyes wander across it for a few seconds), try to get their brains going. The sauropod exhibit manages this by, first of all, being behind a closed door you can’t see through. Usually, the AMNH halls are accessible either through an open doorway, or in a few cases through glass doors. Secondly, the exhibit, especially the rather confined area you enter first, is dark. Very dark. Again a marked contrast to the AMNH’s usually well-lit halls. Just a few plants greet the visitor, and it takes a second to adjust to the dark – enough time to look around a bit and notice the neck and head of Argentinosaurus (fleshed out model) above.
Next, the visitor is channeled along, with only a very few specimens to catch his attention. Well done, because these few pieces (sauropod leg, Komodo dragon skeleton, human skeleton, etc.) focus on getting the main message across (sauropods = way larger than everything else), aided by the largest animals (or their silhouettes) or various groups painted on the wall. Only once the message has been driven home, as I could detect from the comments I overheard, are the visitors released into the main area that contains the sauropod model and the various detail exhibits around it.
The next thing is giving people time to check things out. If you herd them too much, they will get driven along by the masses. That’s why the larger, opener area around the sauropod model and the smaller bits around it works so well: people can sit down to see the projected videos on the sauropod belly, or they can drift around from one specimen or science station to the next.
The stations are not just glass cabinets with some bones in them. Instead, at many of them you can DO things. One allows you to measure either an adult or baby sauropod femur or your own, and then calculate how heavy a sauropod of that size was. At another you can pump a sauropod’s and an elephant’s lung. One I liked very much simply had an unpainted sauropod model, and two sets each (adult and children height) of oculars. One showed a colorful “show-off” version, the other a “camouflage” one. “Which one is true? We don’t know!” is how I’d paraphrase the text that goes with it. One that innocently hides in the corner is among the most impressive: a 5 ½ ft cube (1.7 m, for the civilized) made from Plexiglas filled with sauropod food. A serving sufficient for one day! On it, also, the various plant groups available in the Mesozoic were rated for various factors, getting an easily understood rating in stars. That’s another big thing: make things easily understandable, visualize them!
With all these things well done, there remains only one more thing: make things fun for kids! And the AMNH did just that by adding a kids’ dinosaur dig. OK, it is one of those cheesy things where you use brushes and stuff to brush sand off fossils (cast), but it was done well enough that kids lined up like there was no tomorrow.
Overall, the exhibit gets two big thumbs up from me. If you make it to NY while it is on, or to any of its future stations, go see it! However, as FOR 533 member Steve Perry was quick to point out: if you’re in it only for the size, you’ll be disappointed! Aside from a few isolated bones, not much of the largest dinosaurs (Argentinosaurus and Amphicoelias) is to be seen in bone. It is the biological details that matter! But don’t get me started about the tail musculature, especially the caudofemoralis, of the big model.
And then, there is the other thing about it that is closely tied to shameless self-promotion: the AMNH did not produce a catalogue or anything similar. Instead, the latest book from the “Life of the Past” series (Editor: James Farlow) of Indiana University Press was presented at the press conference. The lucky reporters all even got a free copy! The title is Biology of the Sauropod Dinosaurs: Understanding the Life of Giants, edited by N. Klein, K. Remes, C. T. Gee and P. M. Sander. And by now, I am sure, you have figured out who the authors are … It is intended to be a summary of the research findings of the first (and part of the second) funding period of FOR 533, and yours truly has two chapters in it. The first doesn’t really give much new information; most is already contained in my two papers here and here. The second, however, presents novel research that didn’t make it into the AMNH exhibit. But hey, why spoil the surprise – go and buy our book!) Overall, it is quite a technical book, so laypeople beware, but we did try to make the research as accessible as possible while retaining a high standard. For the even more technically minded there is the summary of our research group’s work (which cost the DFG ~€6.000.000) to be found in Sander et al. 2010. However, reading that paper is not half as much fun as the book, or the exhibit.
- Sander, P. Martin, Andreas Christian, Marcus Clauss, Regina Fechner, Carole T. Gee, Eva-Maria Griebeler, Hanns-Christian Gunga, Jürgen Hummel, Heinrich Mallison, Steven F. Perry, Holger Preuschoft, Oliver W. M. Rauhut, Kristian Remes, Thomas Tütken, Oliver Wings and Ulrich Witzel. 2010. Biology of the sauropod dinosaurs: the evolution of gigantism. Biological Reviews 86:117-155. doi:10.1111/j.1469-185X.2010.00137.x
April 7, 2011
“Sauropods are basically alien animals . . . What can be said of the habits of an animal with the nose of a Macrauchenia, the neck of a giraffe, the limbs of an elephant, the feet of a chalicothere, the lungs of a bird, and the tail of a lizard? With so many plausible but conflicting interpretations, it is unlikely there will be general agreement on sauropod habits as long as more than one paleontologist has an opinion on the matter.”
–Walter Coombs, 1975, “Sauropod habits and habitats”, page 29
I first encountered that passage at age 9, in The Dinosaurs, by William Stout, William Service, and Bryon Preiss. Peter Dodson quoted it in his introduction to the book, and it really stuck in my head. So much so that I quoted it myself when the opportunity arose, and now present it here for your consideration. More recent investigations have pretty well done in the idea that sauropods had trunks (for more about that, go here [which will lead you to this, which I had completely forgotten that I wrote, but quite like now that I’ve rediscovered it]), but the rest of Coombs’s comparisons are still apt. I had no idea when I was 9 how long a shadow the “lungs of a bird” part would cast over my life! And certainly there are aspects of sauropod biology that are still contentious, and some may always be so.
But I really feel like a synthetic view of sauropod paleobiology is emerging, and the best evidence of it to date is the massive paper by Sander et al. (2010) in Biological Reviews. That paper is one of the zillion things I’ve been intending to blog about, but have not gotten around to yet (and there’s a book by most or all of the same folks due shortly from Indiana University Press). When I read it right after it came out, I had the very strong feeling that it was a watershed moment for sauropod paleobiology, such that it will be fair to ask of any future study, “How is this an advance beyond Sander et al. (2010)?” I like papers like that–Coombs (1975) was one such–because they inspire me to start figuring out what’s going to come next.
- Coombs, W. P. 1975. Sauropod habits and habitats. Palaeogeography, Palaeoclimatology, Palaeoecology 17:1-33.
- Sander, P. M., A. Christian, M. Clauss, R. Fechner, C. T. Gee, E.-M. Griebeler, H.-C. Gunga, J. Hummel, H. Mallison, S. F. Perry, H. Preuschoft, O. W. M. Rauhut, K. Remes, T. Tütken, O. Wings, and U. Witzel. 2010. Biology of the sauropod dinosaurs: the evolution of gigantism. Biological Reviews. doi: 10.1111/j.1469-185X.2010.00137.x.