Today sees the publication of a new paper by Michael P. Taylor, Mathew Wedel and myself in which we make a bold and controversial claim: based on data from living animals, we contend that the necks of sauropod dinosaurs - all sauropod dinosaurs - were most likely held habitually in erect poses, and not in horizontal or sub-horizontal poses (Taylor et al. 2009). This research should of course be significant if you're interested in knowing what sauropods looked like when they were alive. However, it also impacts on hypotheses about sauropod behaviour, physiology and ecology [image below by the good Dr Mark Witton. Look for the in-joke].
Ideas on sauropod neck posture have varied a lot over the decades. At least some researchers have proposed that sauropod necks were relatively immobile, horizontal and beam-like (Martin 1987, Martin et al. 1997, 1998). This is thought by others (myself included) to be unlikely, given that there are various indications from anatomy that sauropod necks were reasonably flexible, and held in raised postures (read on). This alternative argument provides at least some sauropods with more erect neck postures in which the neck is shown projecting upwards at an angle of 45 or even 90° to the long axis of the back.
The 'osteologically neutral pose' hypothesis
Palaeontologists have generally assumed that one can get a good idea of an extinct animal's neck posture by simply plugging the vertebrae and skull together, and arriving at a sort of 'best fit' where the zygapophyses (the articulating prongs and facets located on the neural arches of the vertebrae) are in substantial overlap. The resulting pose has been termed the osteologically neutral pose (ONP). Sauropod necks were reconstructed in ONP by Stevens & Parrish (1999, 2005a, b). Arguing that 'with no known exception, the curvature characteristic of the axial skeleton of a given vertebrate arises, not from chronic flexion out of the neutral position, but from the morphology of the vertebrae in the undeflected state' (Stevens & Parrish 2005a, p. 215), Stevens and Parrish reconstructed a variety of sauropods with near-horizontal necks, and they even concluded that some forms (like Dicraeosaurus) had down-sloping necks where the muzzle was positioned close to the ground [adjacent figure, from Stevens & Parrish (2005a), shows [top to bottom] the necks, in 'neutral pose', of Cetiosaurus oxoniensis, Euhelopus zdanskyi and Brachiosaurus brancai].
They haven't been the only researchers to provide some sauropods with down-sloping necks: Wilson (2002) did likewise for Dicraeosaurus, and Nigersaurus has been shown in a similar pose (Sereno et al. 2007). Tracy Ford produced a series of ONP diagrams for sauropod necks, and showed Diplodocus and Apatosaurus with necks that bend sharply downwards in their anterior halves (Ford 1999). The idea that diplodocoids habitually walked around with their heads close to or at ground level seems rather unlikely, if not ridiculous: this would have made them easy targets for contemporary theropods, and it would have made them all but useless at detecting anything that was located more than about a metre in front of them. It also seems totally counter-intuitive that animals evolved such elongate necks purely to eat at ground level.
Stevens and Parrish are just two among many authors who have discussed sauropod neck posture. However, their work has been particularly influential because the diplodocoids featured in the TV series Walking With Dinosaurs were based entirely on the postures and ranges of movement that they reconstructed (Stevens & Parrish 1999). It should be noted that - while they depicted near-horizontal neck postures in sauropods - Stevens and Parrish did infer some flexibility within the sauropod neck, and hence did not limit sauropods to an immobile, beam-like neck posture. However, the ranges of motion they posited seem conservative relative to what might really have been possible. I'll say no more on the subject of neck flexibility, as it's an altogether different topic from the one we're concerned with here.
Does ONP really tell you about the animal's neck posture in life? No, forget it
As it happens, a reasonable amount of literature has been devoted to the subject of head and neck posture in living animals. By X-raying alert, unrestrained animals, Vidal et al. (1986) and Graf et al. (1992, 1995) showed that mammals, birds and lizards consistently do the same things with their heads and necks when in normal alert posture: the neck is strongly extended (that is, the cervico-dorsal junction is strongly bent such that the neck extends strongly 'upwards' relative to the dorsal vertebrae) while the head is strongly flexed relative to the neck (that is, the cranio-cervical joint is strongly bent such that the head is virtually at a right angle relative to the cervical vertebrae*). The 'middle' part of the neck is held relatively rigid, and the neck as a whole is held near-vertical. This is true even of animals that seem to have very short necks, like shrews, rodents and rabbits [the adjacent X-ray shows a rabbit: check out the strongly extended, vertical neck. From Vidal et al. (1986)].
* The terms 'extension' and 'flexion' are going to be used a lot here, so now is time to learn what they mean. When you curl your fingers and form a fist your fingers are undergoing flexion, and when you straighten your fingers, they are undergoing extension. It isn't just fingers that can be flexed and extended, of course: you can flex and extend every joint in your body. If you look downwards, such that your chin is approaching your chest, you are flexing your cranio-cervical joint, and if you look upwards, such that your chin moves away from your chest and the back of your head approaches your shoulders, you are extending your cranio-cervical joint [the terms 'dorsiflexion' and 'ventriflexion', used by some authors, are redundant].
Given what we know about head and neck posture in living animals thanks to X-rays, we can test the claim that ONP really does characterise the posture in life. And the evidence is conclusive: when you plug vertebrae and skulls together in the 'best fit' method mentioned above, you never get the life posture. We did this with skeletons of modern animals (we figure a hare and a chicken in the paper): this is an incredibly basic thing to do, but it may or may not surprise you to learn that no-one has done it before (or, if they have done it, they've never published their results). In both extant mammals and extant birds, vertebrae articulated in ONP produce strongly flexed cervical columns, totally different from the strongly extended cervical columns of the living animals. Furthermore, when you manipulate dry bones alone, you just can't get them to form the strongly extended poses present in living animals. As we say in the paper, 'It is apparent that the soft-tissue of the neck (e.g., intervertebral cartilage) enables greater flexibility in the neck than the bones alone suggest' (Taylor et al. 2009, p. 215).
All of this means that we're severely limited in the kinds of inferences we can make about neck posture from bones alone. We cannot, alas, infer life posture by plugging vertebrae together: it just doesn't work. We can, however, use the X-ray data from modern animals to make inferences about the neck poses of extinct animals.
A phylogenetic perspective
As discussed above, X-ray data shows that the necks of amniotes are extended at the cervico-dorsal junction, and flexed at the cranio-cervical joint. We looked at as many X-rays as we could (some unpublished, but most of them published in papers on neck posture or on the mechanics of respiration), and confirmed these observations in crocodilians, turtles and even in lissamphibians like salamanders. The neck is most strongly vertical in mammals and birds, but some turtles do a good job at maintaining a vertical neck, and monitor lizard and crocodilian necks are held elevated at between 20 and 40°. Even salamanders (which only have a single cervical vertebra) hold the neck elevated, and maintain a flexed cranio-cervical joint.
When we map these details on to a tetrapod cladogram, we have to conclude that extended cervico-dorsal junctions and flexed cranio-cervical joints are primitive for Amniota, and even for crown-group Tetrapoda (there's currently more than one phylogenetic definition of Tetrapoda out there, so let's not worry about the precise content of Tetrapoda right now). Near-vertical, strongly extended necks evolved at least three times within Amniota (Mammalia, Testudines and Aves).
The implications for sauropods
So: what does all of this mean for sauropods and other extinct tetrapods? It means that - in the absence of data to the contrary - we should assume that, when holding its head and neck in a normal, alert pose, a fossil amniote had an extended cervico-dorsal junction (and hence a 'raised' neck) and flexed cranio-cervical joint. Reconstructions which show flexed cervico-dorsal junctions and extended cranio-cervical joints - and this includes the Walking With Dinosaurs sauropods and Nigersaurus as reconstructed by Sereno et al. - are flatly at odds with these predictions and can be regarded as inconsistent with what we know about living animals.
It should be noted, of course, that the 'alert' posture I'm talking about here is by no means the only posture that the animal can adopt. As we note in the paper, the feeding posture adopted by an animal is by no means similar to the normal, alert posture it adopts at other times: look at horses and other grazing mammals, for example.
Some final thoughts
I should note that we discuss other stuff in our paper that isn't covered here. Our conclusions rest on the assumption that sauropods were, while 'extreme', essentially similar to their living relatives in neck morphology. A few authors have proposed that sauropods were morphologically novel, and that they used unusual methods of neck support that made them very different from extant long-necked animals (such as prop-like cervical ribs that acted as ventral compression members, or turgid air-sacs that somehow provided neck support). We disagree with these alternative models, but this isn't the place to smack them down properly: stay tuned.
On another matter, it's recently been argued that the orientation of the semi-circular canals can provide reliable data on head posture. This is an excellent hypothesis, but it's flawed. I'd like to explain this further, but I'll have to direct you to the paper. And - speaking of the paper - the good news is that's available free to all thanks to the good graces of those wonderful people at Acta Palaeontologica Polonica.
There are, of course, additional thoughts on the paper over at SV-POW! Those of you who have followed the story of fame and glory that is SV-POW! (that is, Sauropod Vertebra Picture of the Week) will know that this paper has special significance in that it's the first time that the three SV-POWsketeers have appeared on the authorship of a paper together. May it be the first of many, or at least a few :)
Refs - -
Ford, T. L. 1999. How To Draw Dinosaurs, book 1. T. L. Ford (privately published).
Graf, W., de Waele, C. & Vidal, P. P. 1992. Skeletal geometry in vertebrates and its relation to the vestibular end organs. In Berthoz, A., Graf, G. & Vidal, P. P. (eds.) The Head-Neck Sensory Motor System. Oxford University Press (New York and Oxford), pp. 129-134.
- ., de Waele, C. & Vidal, P. P. 1995. Functional anatomy of the head-neck movement system of quadrupedal and bipedal mammals. Journal of Anatomy 186, 55-74.
Martin, J. 1987. Mobility and feeding of Cetiosaurus (saurischia, sauropoda [sic]) - why the long neck? In Currie, P. J. & Koster, E. H.(eds) Fourth Symposium on Mesozoic Terrestrial Ecosystems, Short Papers. Boxtree Books (Drumheller, Alberta), pp. 154-159.
- ., Martin-Rolland, V. & Frey, E. 1997. Biomechanics of sauropod necks. In Le Loeuff, J., Buffetaut, E., Cavin, L., Laurent, Y. & Martin-Rolland, V. (eds) Second European Workshop of Vertebrate Paleontology, Esperaza-Quillan, 7-10 May 1997, Abstracts. Musee Des Dinosaures (Esperaza, France), unpaginated.
- ., Martin-Rolland, V. & Frey, E. 1998. Not cranes or masts, but beams: the biomechanics of sauropod necks. Oryctos 1, 113-120.
Salgado, L. 1999. The macroevolution of the Diplodocimorpha (Dinosauria; Sauropoda): a developmental model. Ameghiniana 36, 203-216.
Sereno, P. C., Wilson, J. A., Witmer, L. M., Whitlock, J. A., Maga, A., Ide, O. & Rowe, T. A. 2007. Structural extremes in a Cretaceous dinosaur. PLoS ONE 2(11): e1230. doi:10.1371/journal.pone.0001230
Stevens, K. A. & Parrish, J. M. 1999. Neck posture and feeding habits of two Jurassic sauropod dinosaurs. Science 284, 798-800.
- . & Parrish, J. M. 2005a. Neck posture, dentition, and feeding strategies in Jurassic sauropod dinosaurs. In Tidwell, V. & Carpenter, K. (eds) Thunder-Lizards: The Sauropodomorph Dinosaurs. Indiana University Press (Bloomington & Indianapolis), pp. 212-232.
& Parrish, J. M. 2005b. Digital reconstructions of sauropod dinosaurs and implications for feeding. In Curry Rogers, K. A. & Wilson, J. A. (eds) The Sauropods: Evolution and Paleobiology. University of California Press (Berkeley, Los Angeles & London), pp. 178-200.
Vidal, P. P., Graf, W. & Berthoz, A. 1986. The orientation of the cervical vertebral column in unrestrained awake animals. Experimental Brain Research 61, 549-559.
Wilson, J. A. 2002. Sauropod dinosaur phylogeny: critique and cladistic analysis. Zoological Journal of the Linnean Society 136, 217-276.
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we should assume that, when holding its head and neck in a normal, alert pose, a fossil amniote had an extended cervico-dorsal junction (and hence a 'raised' neck) and flexed cranio-cervical joint.
Good point. Sauropods are where the arguments are at, so that's what we focused on in the paper. We did not flog the point that raised necks should be the null hypothesis for ALL extinct amniotes and lissamphibs, including other dinosaurs. But maybe we should have.
Solid writeup. I can say with untarnished objectivity that it is easily your greatest post ever.
Thanks Matt :) I've just started cruising the newswires - we're all over the newspapers and websites today.
To those in the UK: I will be on Simon Mayo's show on Radio 5 Live today, some time between 3-30 and 4pm I think.
Have you seen Ian Sample's piece in the Guardian yet? It begins with "The staid and scholarly world of palaeontology was thrown into rare[sic] turmoil yesterday...".
It gets slightly, but only slightly, better after that...
One thing that does strike me about this research is that it should impact strongly on the assessments of muscle mass and air sac volumes of bipedal dinosaurs. With a bipedal dinosaur, the pose of the head and neck is even more important than that of a sauropod, since at rest the animal is going to have to be more or less balanced on its feet.
So, that means there's got to be the same amount of force in front of the balance point as there is behind it; behind is fixed by the tail posture, but in front the force is determined both by how much weight there is and by what the head posture is, since this determines the leverage the weight exerts. This therefore allows you to make a reconstruction of a tyrannosaurid much more muscular with less volume taken up by air sacs, if the animal kept its head cocked and not stretched out as many reconstructions have it.
It would be interesting to see a properly detailed reconstruction of what forces the teeth and jaws of a T. rex could cope with including the kinetic skull joints; a T. rex skull was not a rigid structure as many simulations assume, but a series of rigid elements linked by slightly flexible joints and linkages. When a skull is shock-loaded then most of the high stress points are at the bends in the structure; if these are not rigid but are slightly flexible then the stress is dispersed somewhat and a much higher shock-loading can be tolerated.
The point of this is that a kinetic skull is much, much more difficult to computer simulate since you cannot assume that all the structure is bone and you have to make intelligent guesses about the strength and so on of the joint areas. However, once you do that then you get a peak loading that the skull and teeth could sustain, which lets you estimate muscle size on and around the skull, which then lets you work out how heavy the head could be, and this then lets you work out the balance of the animal.
Now, I'd bet that a T. rex wouldn't balance in the conventional "head extended" pose, but only in the "head cocked alert" pose. What do you think?
What a week, first 'Laelaps' on Material World and now 'Tet Zoo' on Simon Mayo!
Oh and you can listen live to Radio 5 anywhere in the world if you listen online.
http://www.bbc.co.uk/fivelive/
I know that when they re-articulated the Brachiosaurus at Berlin they made the neck (and tail) more upright, was this related you your work ?
Congratulations!
I wonder only about those animals like pigs and some bears, which walk with the head lowered.
Rather bullish stance from Johnny Natural History Museum in the Guardian article. I wonder if they'd read the paper or just got ambushed with an isolated question.
There are those who prefer them sedated and supine (or prone), and you may find some resistance within the scientific establishment to this attempt to let them get their heads up.
Congrats on yet another high-profile (ahem!) palaeo-behaviour paper! Oh, I'd better go download it now, [CLICKY!].
PS - everything relates to snakes, naturally. Head elevated and flexed = alert. Head level with body or drooping = doing something else (eating, drinking, surface-tasting, probing crevice, sleeping). Makes sense to me, but I'm glad you did the actual work.
Cannot find the in-joke :sulking:
I think there's clue here, find text about Mike Taylor.
This post (and the paper) are full of awesome.
You'd have to ask Paul Barrett about what ever question he was asked, but I think the problem is contextual. The paper doesn't mention museum mounts, and as Mike says (in I think the Independent newspaper) there is nothing wrong with museum mounts in that they all correspond to reasonable positions, they jsut aren't in the upright posture. The way Paul is quoted it looks like an antagonistic answer, but to what? Only what the journlaist put about things in termoil, not what the paper says or how Mike or the paper is quoted above it. If (and I don't know, obviously) he was asked something like"what would you say if I told you that your skeletons are mounted wrongly?" then the answer is reasonable and accurate, and doesn't really contradict what they are saying.
No, really, what's the in-joke? That there are pterosaurs in it? That there are small pterosaurs in it?
Hello, saw you in the news!
I can't help but think their necks could be more extreme, looking at long necked birds, like storks and egrets.
But what gets me, looking at the illustration, is that if they stand with their back legs so straight, their digestive system would be drawn to their heads by gravity. Did they burp a lot?
Are there any creatures that, now-a-days, have a posture in which their back sides are higher than their front end?
Could they have had a bunny rabbit posture or have been like a kangaroo? Kangaroos mostly sort of crawl around unless they're running. Like that Iguana I saw running, actually standing up on his hind legs, and pinwheeling his little front legs in the air. Such a sight!
Just thoughts. And besides, how could they eat enough with that tiny head to sustain that huge body? Questions, questions.
Congratulations on your hard work getting attention!
Melissa
Perhaps the in-joke has to do with this passage :
Oh yeah. For decades it was a Well-Known Fact that Rhamphorhynchus was red. Slightly rusty, but shiny.
By not chewing. I mean, look at the teeth and the attachment sites for the jaw musculature, or just the overall (lack of) robustness of the skull. :-)
Palaeontology pulls the chicks. :D
Good to hear you speak, and I've grabbed the paper for a read later.
Thanks,
Very in injoke.
BTW - do you folks enjoy Zdenek Burian paintings?
Hi all,
Thanks for your interest and feedback. Darren's having a crazy busy day--don't forget that he's got a job and a new baby!--so I'll field some questions.
I know that when they re-articulated the Brachiosaurus at Berlin they made the neck (and tail) more upright, was this related you your work?
Nope, that was all done while our work was gestating, and before we'd told anyone. However, we all three think the remounted Berlin Brachiosaurus is awesome, and it was nice to be able to give it a bit of scientific support.
I wonder only about those animals like pigs and some bears, which walk with the head lowered.
Our paper addresses the unrestrained alert posture, which is not necessarily the same as the posture during locomotion or the posture during feeding. Frequently all three differ wildly from each other. Alert, non-locomoting pigs and bears hold their heads up.
That said, I think this work is a bit of a shot in the arm for browsing sauropods.
Cannot find the in-joke :sulking:
...
Oh yeah. For decades it was a Well-Known Fact that Rhamphorhynchus was red. Slightly rusty, but shiny.
We have a winner! Also, for decades it has been de rigeur to emphasize the sheer brobdingnagitude of sauropods by showing some tiny pterosaurs flying in front of the neck. Rudolph Zallinger's mural is an archetype here, and was the inspiration for our little red Rhampho.
The paper doesn't mention museum mounts, and as Mike says (in I think the Independent newspaper) there is nothing wrong with museum mounts in that they all correspond to reasonable positions, they just aren't in the upright posture.
Yes, thank you! Apparently the only question the reporters could come up with for Paul Barrett was "Are you going to remount your Diplodocus?" Which is asinine. Nowhere in the paper or press release did we suggest that any museums need to take a wrench to their exhibits; in fact, the only time that any of the three of us have explicitly addressed this was in Mike's radio interview, where he said the mounts are fine. We don't expect this paper to be the end of the debate on sauropod neck posture. It's a new data point, but we certainly hope it's not the last one. We wouldn't mess with NHM's Dippy in any case, that thing is a piece of history and needs to not be molested.
We wouldn't mind if they put in a vertical-necked Brachiosaurus right next to it, though. ;-)
In joke?
Emily Bronte-saurus on the right regaling her herd-mates with the latest installment of her classic, Withering Thighs.
This posture then requires extremely high systemic arterial blood pressure and a huge and/or fast heart. I seem to remember that Greg Paul made some calculations on this...are they available on line?
Just back from talking to Richard Bacon (standing in for Simon Mayo) on Radio 5 Live. It went alright I think, but I said a few cringe-worthy/Alan Partridge things (particularly the 'ha ha!' bit). Dinosaurs were very much not the focus: we mostly spoke about Darwinius and evolution (including transitional fossils, cladograms and the nothing-special-ness of Homo sapiens). Unfortunately, or fortunately, it cannot be listened to again.
Your ideas seem plausible and well-thought out, but isn't it likely that there was a great deal of variation in the neck postures of different sauropods? This might have been a basis for ecological niche seperation, especially in the Jurassic, when so many hungry sauropod mouths were looking for food at the same time! I'd love to hear more on this, and I'm sure I will.
Your ideas seem plausible and well-thought out, but isn't it likely that there was a great deal of variation in the neck postures of different sauropods?
Of course! We're not arguing that all sauropods were carbon copies of one another. To pick one example, Dicraeosaurus really couldn't hit the high notes without its vertebrae banging into each other. We're just arguing that the null hypothesis for all sauropods ought to be raised necks, at some angle that almost certainly varied a lot among taxa, rather than ONP.
Awesome paper, gents, congrats. Like I said, I've been excited about this since I read the abstract in the "upcoming papers" section.
What do you fellas think of Brachytrachelopan, who was reconstructed with a perpetually-lowered neck because of the bizarrely forward-sloping cervical neural spines? Seems like such structures would severely limit the upward range of the neck.
Excellent article Darren! For the longest time I had wondered where peoples' common sense had gone when it came to sauropod neck posture. I mean, why evolve (in the case of Diplodocus) a 30-foot neck when all you're doing is picking things off the ground?
P.S. Bless you all for PDFing the paper. It's just too frustrating to not be able to read a paper you desperately want (or need) to simply because no one has PDFed it!
Jerzy posted: "pigs and some bears, which walk with the head lowered."
Extremely unscientific first approximation:
http://images.google.co.uk/images?q=pig%20skeleton
- Looks to me like many of these are showing the "normal posture".
http://images.google.co.uk/images?q=bear+skeleton
- Ditto.
But again, these are NOT x-rays of living animals, and some of them may not be any more accurate than a Rudolph Zallinger painting.
This makes a lot of sense. I collect skulls and sometimes, although rarely, I get a hold of entire skeletons, and recently I finished cleaning an armadillo skeleton. I decided to try to articulate all the vertebrae and when I was dealing with the cervicals things were getting difficult. It became very obvious that there was a lot of curvature in life position that I couldn't replicate without trying to intricately hold them in place.
Also, I imagine that it would take a lot more muscle energy to hold a large heavy neck outwardly for long periods. It's certainly much easier to hold a broom vertically for a long time then it is to hold it horizontally, so I would imagine sauropods would adopt the more efficient posture.
Congratulations.
This looks like a big thing, you'll be cited, like, for 10 years. Also, cool that they sometimes really held their necks in a useful way.
Judging by the behavior of paleontologists, sauropods' heads bobbed like dippy-birds, up one decade, down the next, back up again a generation later.
Skirt hems do the same thing, synchronized with the sunspot cycle. How is a walnut-brained sauropod supposed to keep up with changing fashions in neck posture? At least red rhamphorhynchids are always a safe accessory choice.
OMG drinking sauropod toys.
Congrats on your paper. I'd say you added another big piece to the puzzle of how dinosaurs lived.
Thank you! That low, slanty neck image didn't make sense to me. Every critter I can think of has the ability to raise its head to the limits of its musculature and joints. (Elephants don't raise their heads very far but they don't have much neck.) The idea of having that much length to play with and not exploiting the vertical dimension was non-intuitive. That doesn't make it wrong, just jarring.
Jonny Natural History Museum here. My comments were largely driven by questions from the press relating to remounting skeletons. This seems to arise from information that the Portsmouth University press office was putting about - at least one draft of their press release indicated that museums needed to remount their skeletons. Yes, I have read the paper and did so before I commented.
Perhaps surprisingly, I actually have my own views about what sauropods may have been doing with their necks (published in my case several years ago in papers on sauropod feeding co-authored with Paul Upchurch). Amazingly, some of these diverge from the opinions of Mike, Matt and Darren (you know what, this happens frequently in science folks). I am happy to fess up that I don't agree with all of the suggestions in the Taylor et al. paper for reasons that I do not wish to go into here (though I am happy to discuss this with Mike, Matt and Darren if they so wish, preferably over a glass of wine/beer sometime). I expressed my reservations when asked my opinion by the press - it would have been hypocritical and dishonest of me not to. Simple as that.
Hi, Paul, good to hear from you. As I hope was clear from the various interviews if not from more quote-miney printed pieces, we did try hard to make the point that the low-necked posture seen in (among others) the NHM Diplodocus mount is one of a range that would have been adopted in life. One online report at least -- the BBC's at http://news.bbc.co.uk/1/hi/sci/tech/8068789.stm -- reported this faithfully.
I'll be interested to learn where your disagreements with our paper are -- I'd have thought that it fits in pretty well with the varying-height feeding regimes you and Paul postulated in your 1994 Gaia paper, and the head-and-neck reconstruction we offered is certainly in accord with what you depicted in your figure 5. Or are you alluding to a different paper?
I favor a more S shaped neck profile, but agree with the upright neck. Based solely on coolness.
(I posted this also over at SVPOW):
Iâm all for this paper, great study. But I noticed something missing on the direct testing of head-attitude: Semicircular canals. Is there work to compare the various skulls of sauropods where the inner ear is known to test the position of the horizontal canal, the orientation of this canal relative to head attitude (on Witmerâs work) and the use of the inference of head-neck flexure to the posture of the head?
Another interesting position that seems peculiar, though: I do not think it is simple or easy to infer a rabbitâs short neck (encased in robust muscle) is comparable to a sauropodâs neck, as it is so long, unless it were also as encased or proportionately encased in muscle. Do these questions bear on the topic of the neckâs attitude?
A careful reading of the paper suggests to me that the correct conclusion from the data is not that we now know more than we did before; rather, it demonstrates conclusively that the Stevens & Parrish paper tells us nothing at all.
Before S & P, anyone could entertain any opinion about a sauropod's neck posture, and none could gainsay it. S & P forced raised-posture adherents under cover. This paper restores the status quo ante S & P. The low-brow adherents can grumble about blood pressure, and the rest can hold their heads high again, keeping an eye out for attackers.
Have I misunderstood? Has actual progress been made, or only an error corrected?
Hi Paul, I hope what I commented was not unreasonable. The quotes attributed to you in the Guardian article did look quite 'aggressive' in context to my eye, but that was rather my point. I didn't think you were misquoted, or exactly taken out of context, but it did appear to be a very contrary position to what had been written above it, when in fact the words were (to a degree) in agreement. Perhaps I was over interpreting the media's desire to get an opposing opinion. As I said above, just trying to work it out.
Nathan,
Your comments in regards to the Stevens and Parrish work is curious. Nowhere has Kent Stevens and his work done anything to dismiss the position of vertical neck posture. If anything, Kent Stevens has been extremely open to furtehr work elaborating attitude and static poses, as he has primarily been involved in only range of motion work, even if some of the conclusions this leads to is the average range of motion and general neutral pose in relaxed position should be favored over extreme or active posture. The Taylor paper only offers that active posture is an extreme of the range of motion, and this has been speculated upon since camels entered the discussion. But this also does not mean that the average posture for sauropods agrees with active postures in rabbits, cats, or whatever.
Moreover, some of the taxa in the paper, especially the turtle shown in the "phylogram" figure, is a feeding posture largely seen in browsing or aquatic taxa like the matamata, and are not postures even remotely considered normal or average active poses for terrestrial turtles (given that the matamata takes this pose during lure feeding, it can be considered outside of the envelope for supportive case studies of active postures in neck positions).
Finally, Stevens has actively argued (especially on the DML) that his position is one of neutrality, and that he doesn't actively argue against vertical postures -- only that they are an extreme of the movement envelope, which seems odd as it should case the muscles and tendons of the neck to be under continuous high strain if this was the natural active posture at all times, which is how sauropods were being depicted (as Witton and before him Paul were employing their media to represent). The claim that "vertical necks" went "under cover" seems curious, since no work was done until largely now to actively argue for verticalization in neck postures, aside from off the cuff comments from a variety of researchers. None of these comments were active study and analysis, which is what needed to be done, and this still only argues how animals take verticalized postures in their necks when highly active, but they are short-necked mammals, not long-necked sauropods. There's a level of analysis here that hasn't been done, in my opinion. I am also of the opinion that the nature of the articulations between vertebrae, either central or zygapophyseal, have not been taken into account, and for birds/mammals and sauropods, the centrum/centrum articulations couldn't be more different, and this should influence the amount of flexion in each joint possible (a refutation of the extreme shown in the rabbit and chicken dorsum/neck interfaces in the paper), as well as their attitude. However, aside from crocs (which have a largely horizontal neck even in active postures but have ball-in-socket articulations), who also have short necks, no extant taxa exist today to compare to sauropod morphologies, which is one of Stevens' biggest points. Only explicit comparison of similar morphologies and analyses of ranges of motion can EASILY derive positive data for the study, and this paper only goes so far along this. It says nothing for the "other camp".
Finally, Stevens has actively argued (especially on the DML) that his position is one of neutrality, and that he doesn't actively argue against vertical postures -- only that they are an extreme of the movement envelope, which seems odd as it should case the muscles and tendons of the neck to be under continuous high strain if this was the natural active posture at all times, which is how sauropods were being depicted
OH MY GOD. If you hold a cantilevered beam up, it takes less effort than if you hold it straight out. This is simple, simple physics. It works if you try to hold a broom, or a sledgehammer, or simply a book at the end of your arm. The idea that it took more effort to hold the neck up than it would have taken to hold the neck out is wrong, period.
Stevens & Parrish (1999) argued that holding the neck in anything other than the neutral pose would have required continuous firing of the neck-raising muscles. But putting the neck in ONP just means the zygs are maximally overlapped, it doesn't mean that some magical force has appeared that will support the neck with no muscular effort. Look up the work of Dimery and Alexander on the nuchal ligament in artiodactyls. The only studied artiodactyl in which the nuchal ligament is strong enough to hold up the entire neck and head is the camel, and it can only sling its neck out straight sideways that way. So, obviously, every time you've seen a camel with any part of its neck above horizontal--which is pretty much all the time--and any time you've seen any other artiodactyl doing anything but bonelessly dangling its neck and head, they were firing their neck-raising muscles. Yes, all the time! All day! We do it too--that's why your neck hurts at the end of a long day.
Animals do have lots of clever anatomical devices for reducing the amount of muscular effort needed to sustain their normal poses, but the idea that if they can just get their skeletons into ONP, they won't need to use their muscles any more is unsupported, and unsupportable.
You made the front page of Digg! Celebrate! Or tremble in fear...
http://digg.com/general_sciences/Giant_dinosaurs_held_heads_high
Jaime:
...with the exception of some Galapagos tortoises.
Matt Wedel wrote:
OH MY GOD. If you hold a cantilevered beam up, it takes less effort than if you hold it straight out. This is simple, simple physics. It works if you try to hold a broom, or a sledgehammer, or simply a book at the end of your arm. The idea that it took more effort to hold the neck up than it would have taken to hold the neck out is wrong, period.
Even holding the neck semi-vertically is being held under strain. I never said that the horizontal position was in LESS strain than semi-vertical, only that it is under high strain. Mammals, especially rabbits and such, help minimize this with MASSIVE supportive musculars, from the nuchal ligaments to the trapezius muscles.
But lest we forget one of Kent Stevens' biggest arguments: Sauropods are not mammals. There are enough distinctions, several of which I laid out, that argue that applying mammalian biology to sauropods (especially when the given organisms feature some extreme distinctions in the hypothesized regions of similarity) is a major faux pas barring any other theory. And there was no other theory in the paper. No muscle analysis, no work on head attitude aside from (surprise!) neutral articulation of the head/neck. This is because, aside from assessing energy requirements, natural postures, active envelopes of movement, and postulating muscular components by comparative anatomy, the ability to extrapolate sauropod neck function is almost impossible to decode. This is not to say that that information cannot be useful, but like some other work that has come out this month, it is very possible that some conclusions have been sensationalized for impact, not because they are actually knowable based on the data input. The paper lays out ONE major movement forward: mammals, in all their short-necked glory, have semi-vertical active cervical postures. How this extrapolates to sauropods I have yet to see, especially given the proportionate, component, and mass differences in the groups, not to mention the muscular distinctions between the two, when one of these can only be inferred by inference.
Ooops, duplicate on the last three words, and just messy grammar.
I wonder where arose the notion that placing a joint in an extreme position implies strain. When you stand with your knees locked, that relieves strain on your leg muscles -- until you faint, but that's another story. More precisely, it substitutes bone strain, which is free, for muscle strain, which is not. Ask any slouching teenager.
In the case of sauropods necks, no posture can eliminate muscle strain, but (as has been noted many times) the position closest to vertical does minimize it.
Dartian Wrote:
Also box turtles, sulcatas, aldabra tortoises(taken to an extreme here), wood turtles, and likely many others.
Sorry Jaime, but strongly vertical necks do appear to be pretty common among turtles (cryptodires, at least). In fact, Darren, Mike, and Matt's paper cites a box turtle as their example; not an aquatic turtle.
The paper lays out ONE major movement forward: mammals, in all their short-necked glory, have semi-vertical active cervical postures.
We realize that sauropods were not mammals. This posture applies to all extant tetrapods, including some very long-necked birds (or did you miss Fig. 3?). That does not mean that it held for sauropods necessarily, but it ought to be the null hypothesis. It is certainly possible that because sauropods were structurally extreme, normal rules did not apply to them. But we'd like to see that compellingly demonstrated rather than assumed.
That point (#48) is important Matt: sauropods (well some) *are* structurally extreme. If anything is likely to be default horizontal neck, it is something like a mamenchisaurid. I agree that the null hypothesis should be upright, and the burden of proof should probably be on those who want a horizontal neck, but if I had to pick one candidate (well, apart from frogs) sauropods would be it. As such we do definitely need more research into this area, and I think people would be justified in saying that the debate has not been settled, merely reopened. Still, it'll be fun finding out!
Mike, Matt, Darren - as I said, happy to discuss, but preferably not in an extended fashion on here. I've no objection to sauropod necks being raised some of the time (as you note, I've said this in print), but have reservations regarding it as an habitual posture for all sauropods.
Er, haven't brachiosaurs nearly always been portrayed with near-vertical necks? I have a plastic toy one from the early 1980s which has its neck at about 60 degrees, and am sure i have seen plenty of paintings of them with necks at 90 degrees to reach foliage, the implication being that they spend most of their time with their heads up there...
(Of course, diplodocids are a different matter. But i'd say the pop-culture image of Brachiosaurus is with its head up...)
Also, the long-necked saurischians i see on a daily basis certainly keep their necks angled upwards - in fact, i've hardly ever seen one with its neck horizontal. And they certainly remind me of mini-sauropods...
Read the paper again.
Just... read... the paper... again.
Other points you've missed:
- The paper shows that the attitude of the "horizontal" semicircular canal shows a lot of intra- and interspecific variation and is therefore not a reliable indicator of head posture.
- Stevens & Parrish asserted that the zygapophyses have to stay overlapped by 50 %. In other words, they talked about the extremes of motion, not just the midpoint (the ONP). This assertion is disproved in the paper.
Further:
- The mentioned series of papers by Andreas Christian and various colleagues tried to calculate the pressure (you know, force per area) acting on each centrum in various neck postures and looked for the posture that puts (closest to) the same pressure on all of them. They get the complicated posture of camel necks right. They also argue for a horizontal neck in Diplodocus and a very vertical one in Giraffatitan.
- Do you know what the ONP of the human neck is? About 45° forward. Only seen in trauma victims and Tracy Ford. Why? Well, try it for a day. It hurts; it puts the head-raising muscles under strong strain.
This is slightly off-topic, but it's inspired by Shiva's comment above and it does have at least something to do with erect-necked sauropods:
Tet Zoo readers with long memories may recall this picture from a post Darren wrote way back in April 2008. It's an old-ish picture of a herd of extremely erect-necked Barosaurus. (True to the conventions of illustrating sauropods, there are a few small pterosaurs flying about. They are apparently not rhamphorhynchids, though, and they are not red.)
The picture is from a book published in the, I think, late seventies*. I have fond memories of that volume (I never owned it but when I was a kid, our school library had a copy). It had lots of awesome illustrations, some of them pretty gory; one of my favourites was one where a steel-blue Triceratops rams its horns into the side of a brightly green Tyrannosaurus. But I don't know who the book's author(s) or illustrators were, nor do I know its exact title. Does anyone else know?
* It certainly can't have been published any earlier than 1972, as it had a couple of illustrations of 'Compsognathus corallestris'.
Lots of interesting comments, here, thanks guys. Briefly:
Jaime (#37), the paper DOES discuss head orientation on the basis of semi-circular canals, but we didn't push that angle in the publicity because we knew that we'd be more comprehensible to the civilian public if we told a single story. So far, we've not blogged that part of the paper either, but we will do so (over on SV-POW!) in the next few days.
Nathan (#38), yes -- your summary of the paper is a bit depressing but basically correct: we never expected that this would settle anything (does anything ever really get settled in palaeo?) but that it would at least reopen what has looked worryingly like a closed debate for the last decade. See my comment at the end of the short article http://www.newscientist.com/article/mg20227103.100-giant-dinosaurs-kept… :-)
Jaime (#40): ``The claim that "vertical necks" went "under cover" seems curious, since no work was done until largely now to actively argue for verticalization in neck postures'' -- well, exactly! If no-one was advocating e;evated necks, then the idea was under cover. (Although it's not quite true in any case -- see Andreas Christian's papers on intervertebral stress patterns.) Can you explain what you mean by "a refutation of the extreme shown in the rabbit and chicken dorsum/neck interfaces in the paper"? Also: "aside from crocs (which have a largely horizontal neck even in active postures" -- oh really? Do you have X-rays that show this?
Matt (#41) yes yes YES!
Jaime (#44): "lest we forget one of Kent Stevens' biggest arguments: Sauropods are not mammals". Duh. Why do you think we also looked at birds, crocs, lizards, turtles and lissamphibians? Let me say one more time: we did not find evidence for even ONE extant animal. in any group, that habitually holds its neck in osteological neutral pose. (OK, I know that Matt (#48) made the same point, but it's important enough to bear repeating.)
And finally, Shiva (#51), yes you're right that brachiosaurs have been pictured with raised necks everywhere except in Stevens and Parrish's work and one or two other placed (e.g. the Czerkas reconstruction). That's why we chose Diplodocus for our illustrations -- to show a sauropod that has been depicted exclusively with a LOW neck in recent times.
Hope that's helpful -- thanks again to you all for contributing.
I'm no biologist/paleontologist, but wouldn't an animal holding such a long, thin neck out horizontally be massively vulnerable to predators?
I mean, most carnivores kill long, thin-necked animals by biting at the base of the skull
http://www.kevinschafer.com/wl/images/wllgh1.jpg
http://www.game-reserve.com/gallery/cheetah/images/cheetah_kill.jpg
http://www.kenyasafari.info/images/lion_kill_gnu.jpg
If Diplodocus held it's neck out low and vertical wouldn't Allosaurus attack it in a similair fashion?
According to Wikipedia (Not the best source), Stegosaurus have been found with Allosaurus bite marks on the neck plates...
So if Allosaurus did attack Sauropods like in Walking With Dinosaurs, would this not be good proof in indicating that Sauropods held their heads and necks high, and away from large predators?
Otherwise, wouldn't it would be rather logical they attack the long, massive and exposed juglar/windpipe?
Or am I missing something here?
@Shiva (#51): Wikipedia has a lovely illustration of brachiosaurs with low(ish) neck postures: http://en.wikipedia.org/wiki/File:Macronaria.jpg
(The grey one is Brachiosaurus, the yellow Giraffatitan. The runts are Camarasaurus (brownish) and Euhelopus (green).)
Of course, they're depicted walking - I confess I'm still somewhat unclear exactly what an "alert" posture is.
In comment 54, Mike (quoting Jaime) wrote...
I should add that Mike's 'oh really' should be read in a sarcastic tone. As we note (and figure) in the paper (and as I mentioned in the article above), crocodilians do indeed hold the neck elevated when in alert posture, and we have X-ray data that demonstrates this.
And in response to Andreas (comment 55), 'alert posture' is the normal head and neck pose an animal adopts when it is standing or sitting, relaxed, and not engaged in an activity such as foraging, searching or scanning the environment (the specifics are explained in Vidal et al. (1996) and others of the papers we cite). I should add that 'alert' is used to mean 'non-anaesthetised', rather than 'stressed/on the lookout for danger'.
Thanks to all for very interesting comments and discussion. There is still so much left to do on neck posture, this really is just the beginning.
I always had wondered about predators attacking that lowered neck. This makes much more sense.
Wait, so does this mean that all those old restorations of a diplodocoid's neck being held up swan-like are correct, or does it just mean that the neck gradually sloped upward, say at a lazy forty five or thirty degree angle.
Wait, so does this mean that all those old restorations of a diplodocoid's neck being held up swan-like are correct, or does it just mean that the neck gradually sloped upward, say at a lazy forty five or thirty degree angle.
This very question will be address on SV-POW! in a day or so. Stay tuned!
I'd like to point out on my part that the only thing I talked about when it came to osteological neutral pose was the constraint on expectation of placing skeletons into extremes. The point, as I mentioned in citing Stevens and Parrish on the topic, was that the work only shows the basis from which to derive the hypotheses for posture. Of course, Stevens and Parrish also went on to work out limits of posture using consistent constraints across several taxa, and doing so with flexible or inconsistent metrics by which to position vertebrae would have drawn more heat than they have already received. I was not defending their work, as Kent has done plenty of himself, in opposition to this work; I was remarking on the use of an extreme in one group of animals to describe a posture in another group of animals, where between then cervical morphology and postures are extremely and extraordinarily different. It isn't even enough to say that birds naturally hold their necks vertically (as many birds actively hold their necks in a variety of poses, given the species and length of neck), or even humans (who in many cases, especially mine, had to be trained to hold his neck vertically, as it didn't come naturally and is still painful to do so at times due to enormous pain in the trapezius and inability to rotate the head due to bumping the shoulder, something that a forward, closer to 45 degree posture is not inhibiting), as these are (once again) divergent morphologies and not explicitly comparable to sauropods.
[As an aside, Stevens is, in fact, working on applying his work to other living animals, so I fair expect a response from him on the matter, not that it means much.]
My major point was not to disagree with Mike, Matt and Darren or to argue that they are incorrect. Far from it, as I think they have their facts right. It is their conclusionary stance that I take some argument with, since I think they SHOULD have drawn in more data to clearly state they argument, and should have pulled in more biomechanical data on neck postures to back their claims, and especially brought in biomechanical data from the "sticking straght out" camp (which I do not think actually exists) and refuted it. The claim, rather, stands on an average of normalistic behavior. Their models predict that dorsals and cervicals are held in upright, tense (rather than relaxed, slouched) positions and that this should result in verticalizing trends in the neck. They show, instead, that the neck is virtually straight and flexed at the base with the shoulders, and at the base of the skull. Why then should we not see an S-curved (as in many mammals, including cammels and horses), often highly-S-curved (as in cats, dogs, and hares) swan like neck, rather than a simple elevated beam? What is the purpose of the elongate cervical ribs and often highly elevated neural spines in the cervicals? Do these animals support a massive nuchal complex as in horses and/or bison, where the complex runs from the supportive dorsum up to the skull, suspending at most the neck beneath it and the head on the end? If so, this would enforce that feeding, and habitual stance, is vertical, and I would project, make virtually all sauropods high browsers. This is also an ecological question.
For me, the paper did not answer what I felt were the number of questions that I would have felt needed some explanation prior to its conclusion, and this is no argument on Mike's, Matt's or Darren's part, and I am tending to think the paper was trimmed as a result since knowing Darren -- and what I do know of Mike and Matt -- I will assume more would have been wanted it. But the conclusions seem to jump forward a bit from the argument of "active posture".
A brilliantly obvious comparison that should have been thought of many decades ago.
Surely this big a change in the proposed neck angle would be reflected in the forces applied to the shoulder girdle and front legs.
Sauropods appear to have much less robust front legs compared to the rear. Have any studies been done regarding the maximum forces that the front legs are likely to have been subjected to?
Congratulations on a fascinating Blog and a beautifully researched paper.
WHAT? I go a way for one lousy week and I find a discussion of CURRENT dinosaur news!!! Doesn't this break some kind of blog rule here? I am stunned! Stunned I say! Yet pleased beyond belief
I am tending to think the paper was trimmed as a result since knowing Darren -- and what I do know of Mike and Matt -- I will assume more would have been wanted it.
The paper was not trimmed at all. You may be disappointed that it didn't contain any biomechanics, but it's not a paper about biomechanics. It's a paper about how living animals hold their necks and heads, and the inference that extinct animals probably held their necks and heads likewise. If we had to put the whole paper in one quarter of a page we could just use Figure 3 and be done with it.
That doesn't mean that biomechanics is irrelevant. It's not, and we all sincerely hope that the paper inspires more work--on neck biomechanics, on skeletal morphology and posture in living animals, on the relationships among alert postures, locomotory postures, and feeding postures, etc. We want those answers just as bad as you do, but we don't have them, and we never set out to solve all of the problems with sauropod necks in this paper. It's one argument (well, two, if you count the head stuff). If you don't find it compelling, that's okay. But as we all keep saying, we'd like to see some evidence to the contrary, instead of more assertions that because sauropods were big we can safely ignore what all other tetrapods do.
What I find interesting is that the posture we discuss is so widespread in living tetrapods regardless of size or neck morphology. It's there in tiny salamanders with almost no necks, and little mice with short muscle-bound necks, and big giraffes with long slender necks, and big and little birds with really long, really slender necks. So if you want to argue that it didn't hold for sauropods because their necks were slender, explain why it does hold for flamingos and ostriches and llamas. If you want to argue that it didn't hold for sauropods because they were big, then please explain how you know that there is a break point in neck posture between giraffes and sauropods but not one between giraffes and mice. Such a break point might very well exist, but its existence has to be demonstrated, not just asserted.
I don't understand.
I mean, I've got, like, 10 cm between head and shoulders. It's called "neck"... even the lower jaw (I have an angular process) is far away. What are you talking about? And what are you doing with your trapezius?
Will you come to the SVP meeting this year?
How large would an external air sac inflated with hydrogen, attached near the skull, need to be to give the neck neutral weight? Wolfram|Alpha seems to suggest a sac containing 90 kg of hydrogen, 30 feet in diameter, would provide about a ton of lift, enough to hold up the head and neck with little muscular effort.
It must have started as a crest for mating display, and got inflation and lift just enough, at first, to hold itself up. As it got bigger, it started contributing to neck support, ultimately enabling longer necks. Meanwhile, the surface pattern suggesting looming eyes and gaping jaws made drinking safer.
Promise fulfilled.
Parsimony FAIL. Exploding sauropod WIN! ;-)
If you can bring in boneless aquatic pterosaurs and relictual populations of plesiosaurs in landlocked lakes, I think you'll have the GUT of paleobiological speculation.
A GREAT paper!
I always though giving Brachiosaurus a horizontal neck was just unnatural. Why evolve such long arms and high shoulders if you're not going to reach for the highest possible treetops? If ground ferns was all they were interested in, I expect would have been more short-armed like diplodocus. Plus the strain of holding such a thing horizontally could be literally spine-shattering. With vertical necks... gravity does most of the work!
The comparison to living mammals was also very useful. Even if dinosaurs are not mammals, there's a lot of convergent evolution in similar niches... Mammals have a lot to teach us about dinosaur physiology - perhaps much more so than reptiles. I don't really see a huge amount of reference to living animals in Stevens/Parrish's work, other than that sauropods were not giraffes - which still doesn't say what they WERE like. I've seen giraffe skeletons up close, and their neck bones look a lot more crude, clumsy and actually seem WORSE for vertical posture than sauropod necks.
I also read somewhere that with the proper articulation, the Brachiosaurus neck was straight-up vertical but with a slight S-curve - but that Diplodocus had a mostly horizontal neck that curved up more vertically near the head (more like a "half-U" curve - this way the sharp angle of the Diplodocus head-neck joint didn't force it to perpetually look downwards) To compensate, Diplodocus was more back-heavy so it had an easier time rearing up on its hind legs (being "only" 11 tons also helped) to reach the treetops without a radical change in neck posture.
And in the end we can all agree that a vertical-necked Brachiosaurus is just WAY more awesome!
The "Exploding Sarupod WIN ;-)" comment had me blinking
and scratching my head for a minute, until I pondered
what would happen to a head-erect Brontosaurus*
with a 10-meter hydrogen balloon strapped to its scalp
during a Jurrasic electrical storm...
Terrific post-I was able to follow most of the science,
( always a pleasent surprise ) and its seems fairly sound
thinking to my admittedly untrained mind.
* It may be obselete, but 'Thunder lizards ' are what I
grew up with, dagnabbit.
Craig: "Brontosaurus" is still just fine, as long as you don't capitalize or italicize it except as dictated by context.
What do you think the red pterosaurs were for, if not to draw lightning strikes away from the sauropods' balloons?
Binho (#55): There is a footnote in the Wikipedia article that cites Carpenter et alâs âEvidence for predator-prey relationships: Examples for Allosaurus and Stegosaurusâ; itâs not âaccording to Wikipediaâ.
In Brachiosaurs the fore limbs appear to have become longer than the hind limbs to provide extra height and also perhaps to allow the spine to curve more gradually when the neck was held in a near vertical position. The latter might also have been facilitated by the shortening and downward pointing of the tail.
Hence it does seem that the ancestors of these dinosaurs responded to evolutionary pressure for the head to be held higher by elongation of the fore limbs relative to the hind limbs as well as perhaps by shortening of the tail and further elongation of the neck.
If other sauropods with fore limbs no longer than their hind limbs also habitually held their heads much higher than their bodies, and therefore held their necks in a more vertical position than was previously thought, then I wonder why they do not seem to show the same trend in fore limb elongation as the Brachiosaurs.
I believe that it has been suggested that the necks of other sauropods were held horizontally to act as a counter balance to their tails, which still seem to be accepted as having been held horizontally.
I would also have thought that having a long neck held in a horizontal position would confer upon the animal the advantage of being able to browse across a wide arc at about shoulder height without having to move the body.
I would not doubt of course that other sauropods than the Brachiosaurs could hold their necks more vertically on occasion, and as Nima has pointed out they may even have been able to rear up on their hind legs.
I believe that it has been suggested that the necks of other sauropods were held horizontally to act as a counter balance to their tails, which still seem to be accepted as having been held horizontally.
I have never been able to figure out why, of all the animals in the world, sauropods are the only ones thought to need a counterbalance at both ends. Llamas and giraffes don't have long tails to counterbalance their necks. Elephants don't have long tails to counterbalance their heads. I'm not trying to be snide, I'm genuinely mystified here. I can see how a counterbalancing tail is good for tyrannosaurs and kangaroos, but once animals are down on all fours I think the cantilevered extremities would have to get awfully darn big before a counterweight would be needed at the other end.
It needs hardly be said that the necks and tails of sauropods were slender and would have weighed comparatively little relative to the body, and that all the necks and many of the tails were pneumatic and thus even lighter than they appeared.
I still suspect that the weight of the head of an average elephant might be concentrated closer to the body than that of the tail of a diplodocid or apatosaur was. Giraffes and llamas of course have necks which rise vertically very close to their bodies but this seems rather unlikely in the case of sauropod tails.
Many (perhaps most) quadrupedal mammals use their tails as counterbalances to their head and neck although admittedly the hoofed mammals are not among them.
Giraffes and llamas of course have necks which rise vertically very close to their bodies
Giraffe necks aren't that vertical, and Arabian and Bactrian camels sling their necks way out in front without a counterbalancing tail.
Many (perhaps most) quadrupedal mammals use their tails as counterbalances to their head and neck although admittedly the hoofed mammals are not among them.
Really? As in, you have data showing this? Ungulates from chevrotains to rhinos all get along with non-counterbalancing tails, so I'm not sure that _most_ quadrupedal mammals have tails that could even conceivably function as counterbalances.
Also, just because big cats (for example) have long tails doesn't mean they actually function as counterbalances. Tails can also function as dynamic stabilizers, social signals, built-in blankets for snuggling with, etc. Bobcats and lynxes have essentially no tail but are not noticeably smaller-headed than other cats. Manx cats and dogs with clipped tails don't run around falling on their faces.
I'm really curious: is there any published data supporting the idea that any quadruped uses its tail to balance its head and neck? Or is this just an assertion based on animals that have stuff sticking out at both ends?
I take your point that giraffes obviously do not habitually hold their necks as close to vertical as llamas.
I wonder if the tail used as a âdynamic stabiliserâ could not be considered as a form of âcounterbalanceâ.
As I stated I would agree that hoofed mammals generally do not appear to use their tails as counterbalances, but I think that this is fairly common use of the tail among quadrupedal mammals capable of climbing for instance.
As I stated I would agree that hoofed mammals generally do not appear to use their tails as counterbalances, but I think that this is fairly common use of the tail among quadrupedal mammals capable of climbing for instance.
Now we're getting to special pleading. There are also a climbing mammals who obviously don't use a tail for counterbalance (or have it at all). Many of the Old World monkeys (and not including the apes) have small tails that don't have enough mass to balance squat. Macaques are an obvious example with their short, stringy little tails.
You have noticed that the expanse of your claim has dropped considerably, haven't you? First it was "many or most" quadrupeds and now we're down to just climbers. And now not even all of them.
Matt:
Out of curiosity, are there any published estimates on just how much - or how little - sauropod tails and necks actually weighed?
Surprise surprise, the answers can be found in...
Wedel, M. J. 2005. Postcranial skeletal pneumaticity in sauropods and its implications for mass estimates. In Wilson, J. A. & Curry-Rogers, K. (eds). The Sauropods: Evolution and Paleobiology. University of California Press (Berkeley), pp. 201-228.
- . 2007. Aligerando a los gigantes (Lightening the giants). ¡Fundamental! 12:1-84. [in Spanish, with English translation]
Out of curiosity, are there any published estimates on just how much - or how little - sauropod tails and necks actually weighed?
Not enough. Using graphic double integration or any other digital slicing technique it is easy--and often necessary--to tote up the volumes of the different bits separately, but usually only the sum gets reported. Which is a shame, because comparing across taxa how much necks and tails contributed to total body volume would be a cool study. I think some baby steps in this direction are due to be published in the not-too-distant future, but I can say no more for now.
Matt:
Ah, that sounds excellent! (By the way, Darren: both of your links seem to direct to the same 2007 paper...)
Did no-one know any further details of that dinosaur book I mentioned earlier?
Dartian writes...
Thanks: now corrected.
I took the picture (the individual artist isn't credited as the image was purchased from an agency) from David Lambert's Dinosaurs (Grisewood & Dempsey, London, first printed 1978 but again in 1979 and 1980), but it's certainly apppeared elsewhere. It's based on Bakker's mast-necked barosaurs from 1971, but was clearly illustrated by someone who knew nothing about the true appearance of this animal. Lambert (1978) does feature a flippered Compsognathus corallestris, and a blue Triceratops goring a green Tyrannosaurus in the nether regions, so it might be the book you're thinking of. It's one of several that has many highly memorable, yet technically awful, dinosaur pictures - the stuff I grew up with as a child. Stegosaurus is green with red plates, and ostrich dinosaurs always eat eggs. It would be great fun to gather those images together and write about them, and perhaps I will some time. Incidentally, I used to regularly correspond with David Lambert.
That's a good demonstration of why it's rarely enough to know only the title of a popular dinosaur book you're looking for...
The book was written by David Lambert? Somehow I had thought that the author's name was Taylor (not Mike, alas). But if that's the book that also has, among many other things, illustrations of:
-a Devonian landscape with an Arthropleura
-a bipedal, very theropod-looking Ornithosuchus
-a very Komodo dragon-looking Megalosaurus ripping into a sauropod carcass
-a Triassic sea coast with Placodus, Nothosaurus and Tanystrophaeus,
then Lambert (1978) it is!
LOL! So true! In old books, any other dinosaur can be reconstructed with almost any colour but Stegosaurus is always green with red plates.
Aye, that would indeed be awesome.
-a Devonian landscape with an Arthropleura
Yes, p. 21.
-a bipedal, very theropod-looking Ornithosuchus
Yes, p. 24.
-a very Komodo dragon-looking Megalosaurus ripping into a sauropod carcass
Yes, p. 40.
-a Triassic sea coast with Placodus, Nothosaurus and Tanystrophaeus
Yes, it's across the bottoms of pp. 72-73.
I have Mr. Lambert's 1978 "Dinosaurs" book too, and it contains other questionable images, like the pot-bellied tyrannosaurs, tail-dragging iguanodonts and hadrosaurs, and a Gorgosaurus on page 62 that's so much like a well-known Burian painting that it borders on plagiarism.
He's on the Dinosaur Mailing List...
http://www.youtube.com/watch?v=m2FPG2wXhXY
Haven't thought too much about ancient predatory morphology and whether or not something like this was possible with Mesozoic hunters, but given the subject I thought you'd enjoy this.
Long necks aren't always safe even when held erect! ;-)
Raymond:
To be fair to the artists (I'm pretty sure that book had several different illustrators), much of their work wasn't that bad, considering the level of dinosaur knowledge at the time. But yes, that outrageously ripped-off Gorgosaurus picture - and I know exactly which one you mean - was indefensible even back then.
Matt is being very discrete, but since it's my beans he's protecting, I guess I have the right to spill 'em. :-)
He's referring to a GDI that I did on the two "Brachiosaurus" species for an in-press paper. I found that in Brachiosaurus altithorax, the head and neck totalled 11.87% of the total volume, and the tail 6.49%. In "Brachiosaurus" brancai, the corresponding figures were 14.59% and 5.21% respectively. (The differences are because B. altithorax has a longer torso and a larger tail than its better known relative.)
Note that these are VOLUMES: the relative MASSES of the head/neck and tail would be different, as the head/neck is much more pneumatic than the tail.
I've not been through the same exercise for diplodocids (although I probably will do shortly) -- I expect to see the tail being MUCH more massive in, say, Diplodocus, than the head/neck.
Little late here, but a great post Darren. Not to mention that there weren't abundant grasses in those days, so unless all these huge sauropods were content to crop scrubland or forest clearings, it seems there wouldn't be a lot for them. It does seem like swinging the neck in wide lawnmowing arcs would be energy efficient, but as you point out it would leave the animal not in a good position to spot danger and leaves a vulnerable body part exposed.
It would seem a major advantage of a long neck compared to other herbivores is that it could crop leaves from tree tops or upper branches; young trees and low growing plants may have been very tough or toxic- in New Zealand many forest trees undergo a complete change in leaf morphology as they go from young trees to mature trees, from tough and spiky to the mature form, and this is thought to be an adaptation to grazing by moas, which could reach leaves several meters high. Although so many of the tree species in New Zealand are ancient Gondwanan survivors, so it could well have been something originally evolved to cope with large herbivorous dinosaurs, and continued with the moas (or reverted to that state when the moas evolved/arrived)...
Well I know I'm a little late to this post's party, but over at ART Evolved (the palaeo-art blog), the next big art gallery is Sauropod themed. I was wondering if I could humbly implore you the great Naish to maybe give us a quick public plug either here and/or on SV-POW. That way we might get a lot more modern restorations based on your research in for November.
There is also bound to be some discussion there between us artists that we sure could use some technical expects like yourself and your readers to join in on (and help us from making accuracy mistakes)
http://blogevolved.blogspot.com/2009/09/novembers-upcoming-gallery.html feel free to grab the logo there if you'd like (or contact me on my blog and I can email it)
Hey Darren, I would like to get your take on S-necks in theropods, specifically, the reconstructions by the Discovery Channel that they are promoting heavily in American media right now as part of their "Clash of the Dinosaurs" show this Sunday or something. Most of their reconstructions, in which they are revealing the bone structure in CGI animations, have sort of a lazy, forward-thrust arched neck but not really an S, even after the fashion of the crocodilian in your phylogeny above. Also, the Discovery Channel dinosaurs are notable for being depicted with a goanna-like bulging throat; this is very different from the slender, strongly S-necked, bird-like theropods of Gregory S Paul, where the back of the lower mandible juts out without being subsumed into a throat. Not having watched the Discovery show yet to see what evidence (if any) they are basing this reconstruction on, which do you think is likely to be more accurate/evidence-based? What do you think of the Discovery reconstructions?
Oh, if only CGI documentaries made the science the story and the CGI as a means to get there..instead of the opposite
OK, I am just going to say that pretty much all the critiques I had of the Disco channel program were wrong. Leaving aside the S neck question, which looked natural enough for me, the goanna-like throat of course makes sense because T-rex et al werent taking dainty little bites but wolfing down giant pieces (and apparently dislocating their jaws to do it sometimes). Also, the science in this show was great (thanks in no small part to Matt Wedel); I really got a great sense of the ecology/biology of the various organisms, such as the counterintuitive, strongly r-selected reproductive strategy of the largest land animals ever, sauropods; the possible niche of the various medium size raptors as young-herbivore/sauropod specialists- something they seem well equipped for, since every adaptation- the claws for grabbing, the sickles for stabbing, the small teeth for feeding, the pack hunting- seem specifically attuned to jumping on the backs of large animals; the truly bizarre VTOL pterosaurs hoovering up all the baby dinos running around (although of course both raptors and pterosaurs prolly ate other stuff). Anyway, aside from some shaky CGI for the baby Trexes and sauropods- both of which moved like miniature adults instead of lithe little scramblers like i imagine them- these programs were really pretty good science-based documentaries with the cgi to bring it to life, quite the opposite of previous dino documentaries Ive seen (lots of cool cgi, a dash of science to provide a narrative).
Also, how could I have missed the thing about the T rex throat given Darrens recent 'unsuccessful swallowing' series..sort of one of the boundary conditions for anatomical design, that you are able to swallow the food that you have hunted down and now require to ingest..