September 28, 2015
If we accept that the distinctive ventral projections of the gigantic and ventrally displaced cervical ribs of apatosaurs were likely the base of some form of soft-tissue rugosity — such as keratinous horns like those of rhinos — then does it follow that those necks were used in combat as we suggested?
Maybe, maybe not. As scientists, we are always open to other hypotheses. We’re looking for the simplest, most parsimonious model — the one which best explains the facts.
That’s why we like Mark Witton’s “neck-velcro wall-climbing” hypothesis, as shown in this actual scientific life restoration.
As Mark explained to me, apatosaurs may have used their neck-hooks for more than passive clinging. They may also have been used for inching up the rock-face: first one side of the neck advancing and then the next, in the manner of the “pterygoid walking” that snakes use to progressively swallow large prey.
This is why it’s important to present early-stage work at conferences (and as preprints). Otherwise, you may never hear about important alternative hypotheses like this until after the paper is out and it’s too late to include them.
September 27, 2015
I mentioned last time that, as I sat next to Bob Nicholls in an SVPCA session, I started sketching an apatosaur combat in the hope that my horrible drawing would provoke Bob to do a good one. That worked admirably, which means there is no good reason for me to subject you to my own sketch.
So here it is.
I think the main lessons to draw from this piece are:
- I can’t draw heads.
- I can’t draw limbs.
- I can’t draw torsos.
- I may be just about capable of drawing tails.
During a break, I asked for Bob’s advice on how I can do better. I know I’ll never be an artist, but it’s fun to sketch (especially during mammal talks) and I’d like to improve a little. The main point Bob made was to think about where the light is coming from. Be consistent about that, and you get an immediate improvement in realism.
So here’s what I sketched the next day, with that in mind:
So what have we learned this time?
- I didn’t consciously do this, but I ended up with a composition kind of similar to what Bob came up with, but worse.
- In my desire to achieve the intertwined-necks pose, I made the necks too long and thin.
- I still can’t draw heads.
- Let’s just forget about the hindlimb of the one on the left.
- Uh, and let’s forget the torsos, too.
- But at least the light is coming from top right!
In short, as Stephen Sondheim put it, art isn’t easy. I wish I had more time to put into it.
The real moral of this story is: if I had a crack at drawing fighting apatosaurs, you definitely can. Let us know if you do — leave a comment. We’ll gather people’s contributions in a future post.
September 25, 2015
On the morning of Tuesday 1st December, on SVPCA day 1, I gave my talk about apatosaur neck combat. In one of the afternoon sessions, I sat next to Bob Nicholls, and found myself thinking how awesome it would be if he sketched some apato-combat.
But I didn’t want to come right out and say “Hey, Bob, how ’bout you spontaneously illustrate our palaeobiological hypothesis?” So instead I used a tactic that Fiona often uses when she wants me to do something: she starts to do it herself, badly, and waits for me to take over. (This is often how I find myself cooking in the evenings.) In the same spirit, sat next to Bob, I started a horrible sketch of wrestling apatosaurs. Sure enough, Bob, saw what I was doing, internally decided it ought to be done properly, and produced this:
What I love most about this (beside the casual way he knocked it out in fifteen minutes) is the sense of heft about the apatosaurs. These are big, solid animals. Someone’s gonna get hurt.
September 20, 2015
Last time, we looked at some of Brian Engh’s preliminary sketches of pieces to illustrate our fighting-apatosaur hypothesis. But there’s more: some way into the process, Brian also came up with this very rough sketch, illustrating a different style of combat:
All the pictures in the previous post show various forms of ventral-to-ventral combat, but we’ve also been thinking about possibilities, and an important one is ventral-to-dorsal.
That could work in at least two ways. We can imagine a wresting match, where each animal tries to get its neck above its opponent’s, and to force it to the ground. There is precedent for this in the behaviour of various extant animals. (Or perhaps I should call it postcedent, since apatosaurs came first.)
But other extant animals have a much more violent combat style, based on striking blows rather than exerting steady force. Notably, giraffes do this, using their long necks as levers to crash their uncharismatic, highly fused mammalians heads into each other.
Could apatosaurs have done this? Not exactly: their heads were far too small to be effective clubs, and far too fragile to survive being used in this way. But the necks themselves would have been formidable weapons: we’re confident that apatosaurs striking blows would have done so with their necks, bringing them powerfully downwards on their adversaries.
Brian liked this idea enough to work the rough sketch above up into a completed drawing, which we also plan to include in the paper (and which, by the way, I unreservedly love):
So what style of combat did apatosaurs use? Ventral-on-ventral shoving? Wrestling to the ground? Striking downwards blows with the neck?
My best guess (and it’s only a guess, necessarily) is that among the half-dozen or so recognised species of apatosaurine, all these styles were likely in use. And this may explain the variation in cervical morphology that we see between species (though of course ontogeny and sexual dimorphism may also be at work).
In short, I think all of these scenarios are credible — and therefore perfectly legitimate subjects for palaeo-art *hint hint*.
September 19, 2015
In putting together our thoughts on how apatosaurs used their necks, we were motivated by genuine curiosity — which in Matt’s and my case, at least, goes back many years. (We briefly discussed the problem, if only to throw our hands up in despair, in our 2013 neck-anatomy paper.) We didn’t land on the combat hypothesis because it’s cool, but because it’s where the evidence points.
That said, it is cool.
Brian Engh is on the authorship for this paper largely because of his insights into extant animal behaviour. But there’s no denying that it’s a real bonus that he’s also an awesome artist. He’s been putting together sketches to illustrate our hypothesis for some time, partly with the goal of figuring out which compositions to work up into finished pieces. Here, with Brian’s permission, are some of those preliminary sketches.
First, a really nice sketch showing a ventral-to-ventral shoving match from down at ground level.
I really like this one, and would have been happy for it to be one of the anointed ones. I like the sense of huge beasts towering over the viewer. That said, I always love pencil sketches, often more than I do finished pieces, so I’m not too unhappy that the world gets to see this one in pencil-sketch form.
Next up, sketched more roughly, is a concept for a different form of combat in a different aspect. Here, we see two animals side by side, wrestling with both necks and tails.
I like the dynamism of this one, and especially that the one on the right is in the process of being pushed over. But there’s nothing in apatosaur tail morphology that particularly says “combat”, so I guess I’m not too unhappy that this one didn’t make the cut.
The third sketch shows two individuals rearing into into ventral-to-ventral push.
Matt and Brian liked this one the most, so it got worked up into a finished and coloured piece which will be one of the figures in the paper when we get around to submitting it. Here is the current version — as I understand it, Brian plans to revise it further before it’s done.
The craftsmanship here is superb, but I can’t help regretting that the dinosaurs are rearing less than in the sketch. I feel it’s lost some of the power of the concept sketch.
What you’re seeing here, folks, is a bona fide instance of co-authors disagreeing. Happens all the time, but you usually don’t see it, because it’s all resolved by the time the paper is submitted. Brian is the artist, and ultimately it’s for him to decide what to depict and how; but I’ll always be glad that we still have the pencil-sketch as well as the finished version.
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.
September 9, 2015
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:
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.