Dinosaur Posture Still Wrong, Says Study

An anonymous reader sends along a piece in Cosmos about new dissension to the current prevailing wisdom on dinosaur posture. The researchers admit that blood pressure presents an unresolved obstacle to their model of dinosaur heads held high. "The current depiction of the way giant sauropod dinosaurs held their necks is probably wrong, says a new study. 'For the last decade the reigning paradigm in palaeontology has been that the big sauropod dinosaurs held their necks out straight and their heads down low,' said co-author Matt Wedel, who researches biomechanics at the Western University of Health Sciences in Pomona, California. But 'our research [now] suggests that this view of sauropods is simply incorrect, based on everything we know about living animals,' he said." The researchers worried that some other team might beat them to publication, so obvious did they consider their methodology of looking at living animals to gain insight into the biomechanics of extinct ones.

Comments

AW...

[The Living Fractal]

Guess this means there was no Stuckupasaurus? You know, the snooty dinosaur who thought it was better than all the others and walked around holding its head high and looking down its nose at the others? ...ok, wow, THAT was lame.

I apologize.

TFA Is slashdotted

[TinBromide]

So they looked at a giraffe and decided that the giraffe may be a suitable long-necked living animal? Unfortunately TFS only says that the horizontal configuration is incorrect, and I can't get to the article to see how they posit that long-necked animals posture themselves. So, I'm suggesting that the long neck is held vertically as a way of gaining extra height for food reach, reaching the ground, and longer range vision without the increased bulk of longer legs, taller body, etc.

Re:TFA Is slashdotted

[MozeeToby]

The with the vertical posture is blood pressure and the energy required to move blood to the head. Supposedly, just moving blood up the neck to the head would require have the dinosaurs energy and a heart 15 times bigger (as a ratio of body mass) than the hearts of other large animals.

Re:TFA Is slashdotted

[Red Flayer]

So, I'm suggesting that the long neck is held vertically as a way of gaining extra height for food reach, reaching the ground, and longer range vision without the increased bulk of longer legs, taller body, etc.

Not only that, but I'd conjecture that the long neck must have evolved vertically. The musculature required to hold a long neck like that horizontal must be enormous, and hardly an efficient way of bearing weight. Plus, is it any coincidence that the large dinosaur neckbones look kind of like hip bones, the primary vertical weight-bearing bone in people?

And the BS about the massive tail counterbalancing a long neck... for that to work as an opposing force on the neck, with the body as a fulcrum... well... that would required the spine to be pretty rigid. I'm not sure how well that would work in practice.

On a side note, have you ever seen a giraffe try to reach the ground with their head? It's pretty amusing. It reminds me of myself, trying to pick up my kids crayons from the floor... it's a whole lot of effort (what? so I'm not in shape or flexible. That's normal here, right?)

Re:TFA Is slashdotted

[TinBromide]

Since I couldn't get to the article (still can't), I was extrapolating the posture of living long necked animals. Off hand, I can't think of any long necked animals that don't keep it in a vertical configuration, it seems like it'd be a waste to have a long neck without the defensive/food advantages that go along with it. It'd be like bats evolving wings, but not having the pectoral muscles to flap them enough to fly.

Re:TFA Is slashdotted

[whiledo]

Yes, it is rather awkward. Not the best video I've seen, but the best I could find on youtube. I've seen some where it's a much longer drawn out process.

When you see giraffes doing the neck-slapping thing, you can see how when their necks bend sideways, it's not a continuous curve but rather like a low-grade 3d render of one with vertices at each vertebra.

Re:TFA Is slashdotted

[Captain Hook]

But having a 15 ft long neck which is held horizontal means you can browse a 30ft wide path without moving (or perhaps while moving slowly in one direction), the energy saving for being able to browse a large swath of ground without moving must be large when you weight a few tonnes.

Re:TFA Is slashdotted

[Useful Wheat]

You need a larger imagination. You have successfully described flying squirrels. I think they fit the category nicely for bats with wings that cannot fly. Go over to wikipedia and look at them for yourself. http://en.wikipedia.org/wiki/Flying_squirrel

They also have flying possums, but they lack the name recognition (thanks Rocky and Bullwinkle!).

As an engineer, I have to design pumps to move fluid through pipes, and one of the biggest factors you have is the height at the destination of the fluid. Running this calculation right now, a mere 1 foot of height increase is roughly the same as pumping something an extra 20 feet. Now that might not seem like much, but add 10 feet of height to a line (such as a vein in a neck) and you are looking at 200 feet of pipe.

Re:TFA Is slashdotted

[Anonymous Coward]

But having a 15 ft long neck which is held horizontal means you can browse a 30ft wide path without moving (or perhaps while moving slowly in one direction), the energy saving for being able to browse a large swath of ground without moving must be large when you weight a few tonnes.

Ever held your arm out straight and put a large book on your palm & tried to keep from moving? The idea that solving for the blood pressure problem by having horizontal necks makes more sense than solving for the muscle fatigue problem by aligning the neck vertically is ludicrous.

Re:TFA Is slashdotted

[Binestar]

http://www.unmuseum.org/dinobront.htm

Today, scientist's vision of the habits and habitat of the Apatosaurus are quite different than what Marsh and other early paleontologists had thought. Early analysis suggested that the animals must have been weak because their small heads could only chew the minimum amount of food necessary to fuel such a big body. So weak, in fact, that large sauropods were thought to be slow, unable to lift their bulky tails off the ground and only able to support their massive weight by living in shallow lakes and swamps where water floated their bulk.

Paleontologists like Bakker showed that this image was wrong. No Apatosaurus skeleton has been found in an ancient body of water and its feet were not at all suited for walking through marshy and muddy ground. In fact, Bakker notes in his book Dinosaur Heresies, an analysis of changes in geology over time suggest that large sauropods moved out of areas as they became wet: they didn't like swamps at all.

Re:TFA Is slashdotted

[Golddess]

Try standing perfectly still for hours on end, not flexing your legs even one bit. Sure, circulation will still happen (it's not like the circulatory system is one single loop, it's more like a beltway with various on/off ramps to do your thing in the city, then get back on the beltway in a totally different location), but blood will pool in your legs and it can cause issues by stretching out your veins and you'll start to feel light-headed and might even pass out.

As a results, veins are basically one-way valves. By flexing your muscles, you constrict your veins, forcing the blood within to go in the only direction they allow (back towards the heart).

Re:TFA Is slashdotted

[Anonymous Coward]

Not really, giraffe's have valves in their neck arteries -- hence you don't need insane amount of blood pressure from the heart (the valves keep the blood from falling down after being pushed up).

My guess is that these long-necked dinosaurs probably had valves in their arteries just as giraffes do today...

Re:TFA Is slashdotted

[wildsurf]

When thinking about dinosaurs' long necks, it's helpful to consider the possibility that the atmosphere was much thicker back then. So fluids could be drawn much higher without introducing vacuum problems, and it also explains how such huge insects and proto-birds (e.g. pterodactyls) could have flown there. Interesting stuff.

Re:TFA Is slashdotted

[Richy_T]

Do they take account of the fact that the blood comes back down again? You might need a heart that size if you are pumping the blood at atmospheric pressure but if you keep the pressure built up on the veinous side, you just need to provide a pressure differential and to overcome viscous resistance.

Re:TFA Is slashdotted

[maxume]

I'm pretty sure gravity is the problem, not vacuum (just carry some decent amount of water up a flight of stairs if you doubt this).

Re:TFA Is slashdotted

[init100]

Not really, giraffe's have valves in their neck arteries -- hence you don't need insane amount of blood pressure from the heart (the valves keep the blood from falling down after being pushed up).

Actually, most (all?) animals with a circulatory system have backflow prevention flaps in their veins. Having them in arteries is just a simple extension to this concept.

Re:TFA Is slashdotted

[nyctopterus]

Most people who study the aerodynamics of pterosaurs don't think they would have had a problem flying in today's atmosphere. the thicker atmosphere stuff is definitely fringe science.

Re:TFA Is slashdotted

[nyctopterus]

That is in a forthcoming paper according to their blog SV-POW! (Sauropod Vertebra Picture Of the Week.)

Re:TFA Is slashdotted

[Mr. Slippery]

it's helpful to consider the possibility that the atmosphere was much thicker back then

Thicker? Quite possibly. But 370 atmospheres? That link is the best crank science since the Time Cube, man.

Re:TFA Is slashdotted

[againjj]

The original paper (at http://www.app.pan.pl/article/item/app54-213.html) basically says that the "osteological neutral pose" (ONP) (basically the pose where the bones make maximal contact with each other) is not necessarily the pose most commonly held. Apparently, the first and only good study of neck and tail position concluded that the then currently accepted pose was unlikely and that ONP was probable, and then every one else simply accepted that without further study.

The authors went looking at current animal poses and concluded two things. First, in modern animals, ONP is not always the pose held by default, and in fact assuming ONP as default in sauropods has some difficult-to-explain ramifications (though a vertical default does as well). Second, even if ONP is the default pose, there is generally much movement away from that pose for various activities in modern, like drinking and running, and so it is likely that sauropods had that too.

The authors also, of course, hedge their bets and say that their ideas may be totally off if there is something they aren't aware of, like specialized tendon structure for the neck or other such things.

In short: the authors say that the conclusion that sauropods have horizontal necks was based on assumptions that are unsound.

Oh, and TFA:

BRISBANE: The current depiction of the way giant sauropod dinosaurs held their necks is probably wrong, says a new study.

"For the last decade the reigning paradigm in palaeontology has been that the big sauropod dinosaurs held their necks out straight and their heads down low," said co-author Matt Wedel, who researches biomechanics at the Western University of Health Sciences in Pomona, California.

But "our research [now] suggests that this view of sauropods is simply incorrect, based on everything we know about living animals," he said.

Unrealistic posture

According to the report in the report in the journal Acta Palaeontologica Polonica, sauropods held their necks up in the same way as many living vertebrates, in a swan-like 's' curve, rather than in the horizontal pose commonly shown in everything from museum reconstructions to plastic toys.

For many decades, scientists supposed that sauropods had long necks so they could browse high in the treetops and depicted them, like giraffes, with their heads held high. But a 1999 Science paper led to a shift in the way sauropods were shown.

The authors of that paper argued that the habitual pose of an animal's neck could be easily found by lining up the vertebrae in maximum contact, which gave a horizontal pose for most sauropods. Estimates of blood pressure also suggested that it would have been very difficult for sauropods to pump their blood up to such a height.

Blood pressure problem

"The problem is, living animals don't hold their necks in that posture," Wedel said. After stumbling across a paper from the 1980s that showed that most land animals held their necks vertically, Wedel's team looked for clues to sauropod posture in X-rays of living animals.

They found that reptiles and amphibians held their necks mostly horizontally, while mammals and birds (which are more closely related to dinosaurs and share their upright leg structures) all held their necks vertically.

Studying the neck movements of living creatures also suggested that sauropods had a greater range of movement than previously thought.

While scientists had assumed that the dinosaur neck vertebrae overlapped each other by around 50%, that's not true for living creatures like ostriches and giraffes, which can extend their necks till the vertebrae hardly overlap at all.

Their method was so simple that the team was worried someone else would publish the findings before they could. "We did get a bit paranoid... it just seemed so obvious that if you want to know what extinct animals did, you shoul

Re:TFA Is slashdotted

[TinBromide]

wings provide lift and they're balancing the up force on the wings against the down force of the body with massive pecs.

Re:TFA Is slashdotted

[TinBromide]

As an explanation of my above post, the wings are supporting the body due to the lifting force applied to the wings balancing out the gravity of the torso. The joints lock into place and prevent the wings from forming too much of a V shape. If you've ever broken apart a whole chicken, you'd feel the resistance put in place when you try to put the wings at more than 90 degrees perpendicular from the body. Its the same reason why you can't reach stick your arms straight out from the body at 90 degrees perpendicular to the body (similar to the pose in leonardo da vinci's man-in-circle sketch), and bring them much further back without twisting, the bones prevent it. (I know you can touch your hands behind your back, but that's not the positions birds fly in)

Re:TFA Is slashdotted

[Minwee]

I'm pretty sure gravity is the problem

Well that's simple, just change the gravitational constant of the universe.

Re:TFA Is slashdotted

[shess]

I can't did up the reference right now, but it turns out the eneregy requirements for maintaining the long neck outweigh the cost of simply walking to the food.

Meaning dinosaurs did not have long necks. QED.

Re:TFA Is slashdotted

[rtb61]

Of course if you had any dinosaurs left you could check to see whether major arteries were enclosed in musculature which assisted pumping the blood. Of course this evolutionary trait would be restricted only to major sauropods due to the inherent energy waste where it is not required and then perhaps only in the neck.

Re:TFA Is slashdotted

[Sulphur]

If a few veins or arteries had peristalsis (distributed pumping), then the pressure difference could be less perhaps?

Re:TFA Is slashdotted

[fractoid]

Ever held your arm out straight and put a large book on your palm & tried to keep from moving?

Reptile muscles work differently to mammalian muscles, I believe. That's why reptiles can hold awkward poses for hours at a time, while mammals tend to keep moving. Also, there's a difference between slow and fast muscles - you don't have any trouble holding your head balanced on top of your neck for 12 hours at a time, which actually takes quite a lot of strength. Contrariwise, your arm will contain mostly fast muscle fibres (unless you're a yoga or tai chi master) because it requires more strength on a much lower duty cycle.

Two Things

[eldavojohn]

Why are we arguing over which position was the default when it's entirely possible that they utilized both positions. Down low for traveling to avoid blood pressure problems and up high for brief states of alert or reaching high food sources? With the flexibility of the vertebrae, I would assume the animal would use it however it most suited them for the time being.

The other thing is how much do we know about the tissues and proteins that made up muscles and blood in Sauropods? Is it possible that they were much stronger or their blood had different properties making it capable of overcoming the blood pressure problem?

I've seen exhibits that portray them both ways. You just might have to accept that you're never going to know for sure ...

... until you CLONE THEM!

*starts humming the Jurrasic Park theme song with a creepy grin on his face*

Re:Two Things

[MaXintosh]

Clone them, or get some better impressions of soft tissue. I expect we'll eventually get some, given our history of finding such neat things, but I'm not holding my breath because it's like finding a needle in a haystack.
Er, well, actually more like finding a rock among a planet full of other rocks.

Re:Two Things

[spyfrog]

Well, then cloning have given us a cool dinosaur that we could use both to fix our lawns and to trim our trees! Multipurpose dino.

Re:Two Things

[techess]

I agree until we get a better idea of the soft tissue we won't really know.

Giraffes have a very cool way of improving their circulation without just throwing a bigger heart at the solution:
http://news.softpedia.com/news/Some-Weird-Giraffe-Issues-80555.shtml

"To pump the blood high to the brain, the heart of the giraffe is very large: up to 11 kg (25 pounds). The heart pushes 60 liters of blood per minute. The muscles of the neck arteries are relaxed with each heart beat, helping the propulsion of the blood to the brain. In the neck veins, special valves impede the blood to flow back too rapidly, meanwhile preventing the emergence of a syncope (fainting due to sudden lowering of the blood pressure). At the base of the feet, where pressure is low, there is a system of capillary vessels like in humans, impeding the appearance of edemas. Like humans, the giraffe is one of the few vertebrates which is taller than longer, and NASA studied blood circulation in giraffes for creating an anti-gravity garment for astronauts."

Also horses while not having an extremely long neck also deal with circulation problems by more than throwing in a bigger heart.
http://en.wikipedia.org/wiki/Circulatory_system_of_the_horse
The frog
Each hoof contains a structural component known as the "frog," which covers the deeper structure of the hoof known as the digital cushion, a vessel-filled tissue. When the horse places weight on a leg, the ground pushes upward on the frog, compressing it and the underlying digital cushion. This results in squeezing blood out of the digital cushion, which then helps to pump it back up the leg, helping the heart to work against gravity.

Nature has done some amazing and unique things with soft tissue to get around limitations. It would be so interesting to find out how dinosaurs worked and what their bodies were really like.

Re:Two Things

[lgw]

Giraffe's have a rete mirabile to avoid the head exploding when lowered. This sort of structure has evolved seperately in several unrelated species, so it's quite reasonable that the long-necked dinos had them. The dinos probably didn't need a large blood supply to the brain, the way a mammal does, so the requirements might not be so bad.

Oh, come on

[Daniel Dvorkin]

It was only 6000 years ago -- didn't anyone get any pictures?

Listen to your mother.

[Anonymous Coward]

Sit up straight! Eat your palm trees! Don't ROAR at your sister! Ignore those tiny furry mousey creatures...they are of no consequenc and won't amount to anything!

Re:Listen to your mother.

[je ne sais quoi]

...I don't care if the neighbors are evolving into birds, we're not doing it. If they were evolving to jump off a cliff, would you do it too? And for the last time, that giant bright spot in the sky the last few days is not an asteroid that will kill us all. I swear, kids these days and their wacky imaginations.

Re:I'm horny

[The Living Fractal]

...brings a whole new meaning to "multi-touch"... and, no.

geese

[Red Flayer]

Well, that was a quick slashdotting. Hopefully they'll be back up soon.

Re: modern pseudo-analogues -- based upon the geese I raised as a kid, I never could quite grok the 'head-held-low' posture. Geese only hold their heads low to screw or to attack. It seems very inefficient for a large creature to hold that much weight horizontally away from the body (remember those physics lessons re: levers and distance from the fulcrum?).

Dinosaurs are awesome, as most five-year-olds will tell you. Armchair paleontology is fun too. And since we slashdotters are so fond of pretending expertise on subjects we know little about, and TFA seems to be slashdotted, I'm looking forward to a very amusing (but maybe not quite so enlightening) discussion.

Re:geese

[eldavojohn]

Re: modern pseudo-analogues -- based upon the geese I raised as a kid, I never could quite grok the 'head-held-low' posture. Geese only hold their heads low to screw or to attack.

I think it's dangerous to try to compare a two legged winged creature to a four legged creature but from the article:

They found that reptiles and amphibians held their necks mostly horizontally, while mammals and birds (which are more closely related to dinosaurs and share their upright leg structures) all held their necks vertically.

Studying the neck movements of living creatures also suggested that sauropods had a greater range of movement than previously thought.

While scientists had assumed that the dinosaur neck vertebrae overlapped each other by around 50%, that's not true for living creatures like ostriches and giraffes, which can extend their necks till the vertebrae hardly overlap at all.

And in regards to efficiency of the way they hold their neck:

It seems very inefficient for a large creature to hold that much weight horizontally away from the body (remember those physics lessons re: levers and distance from the fulcrum?).

(As the article notes) it's probably a lot harder to have the blood pressure to pump blood all the way up that column to the head. Blood pressure is one of the things they can't explain about their model. The article says, "Estimates of blood pressure also suggested that it would have been very difficult for sauropods to pump their blood up to such a height."

Dinosaurs are awesome, as most five-year-olds will tell you. Armchair paleontology is fun too. And since we slashdotters are so fond of pretending expertise on subjects we know little about, and TFA seems to be slashdotted, I'm looking forward to a very amusing (but maybe not quite so enlightening) discussion.

After reading it, the article's not as great as you think. There's plenty of pictures on Wikipedia of the animals depicted both ways.

Re:geese

[Red Flayer]

I think it's dangerous to try to compare a two legged winged creature to a four legged creature

Yes, I know it's dangerous, which is why I only make that comparison in a hardened secret laboratory. Last time I tried it, the explosion nearly blew through the 2nd-level blast enclosure.

Seriously, though, modern birds may be the closes living relatives to dinosaurs. And while I'd very strongly suspect that the long neck of geese evolved independently of the long necks of sauropods, it may be relevant.

(As the article notes) it's probably a lot harder to have the blood pressure to pump blood all the way up that column to the head.

Yes, this is an ongoing issue, and one of the primary reasons the position du jour has been lowered-head. But there is a ton we don't know about dino biology, and it is quite possible there are alternate means of pumping blood up the column (such as smooth-muscled vasculature that could help pump, especially in concert with valves like those in giraffes and other animals used to cut off blood flow temporarily. Or perhaps blood demands are low, and periodic lowering of the head could supply enough oxygen et al for survival. It's all conjecture... but it still makes me wonder if the net energy demands of maintaining a horizontal position would be greater than the demands of pumping blood and keeping the vertebrae vertical.

After reading it, the article's not as great as you think.

Hey, I never made a value judgment on the quality of the article. :) I just meant that typically the article being available for perusal guides the discussion somewhat... without TFA, the discussion tends to be more freeform and devolve into inanity quicker. Not that there's anything wrong with that.

Straighten up and fly right!

[awb131]

That's going to kill my karma, but I thought it was funny.

Informed speculation

[MaXintosh]

This is all informed speculation - interesting, and it generates a testable hypothesis, but hardly revealing. There's a hundred different ways to go on the issue until they find impressions of soft tissue. The authors (of the paper, not TFA) hedge their bets heavily by saying that IF sauropods are directly comparable to extant taxa... a bet I wouldn't take myself, since sauropods seemed to form a morphoniche we don't see _appreciably_ filled in extant groups (obvious exception excluded).

For people who want their science undiluted, here's the paper: http://www.app.pan.pl/article/item/app54-213.html
Head and neck posture in sauropod dinosaurs inferred from extant animals
Michael P. Taylor, Mathew J. Wedel, and Darren Naish
Acta Palaeontologica Polonica 54 (2), 2009: 213-220

Re:until you CLONE THEM! - Nope

[the_humeister]

I don't know about yours, but my time machine only goes back to 4004 B.C.

Occams razor tells me

[Anonymous Coward]

The long necked dinosaurs simply tied their long necks into a knot whenever they needed to raise their heads for feeding and observations.

They had a symbiotic relationship with the horned dinosaurs who were needed for untieing the knots.

Coiled up on top

[hoggoth]

Come on people, CLEARLY the large long-necked dinosaurs kept their necks curled back and their heads resting on top of their backs.

Re:I'm horny

[mrdoogee]

There's an app for that!

Re:There is a theory

[dtolman]

I'm sorry, but reading this completely unrelated tangent, the only thing I could think of was:

Oh yeah, the important thing was that I had an onion on my belt, which was the style at the time.
They didn't have any white onions, because of the war. The only thing you can get was those big yellow ones...

Re:Gravity...

[greywire]

It is psychotic. Because they say they don't believe in the science, but then try to come off sounding educated and using science to disprove the science.

What's really sad is all the people out there who believe them and never do any research themselves to see their pseudo science doesn't jive.

Author's response to points raised in the comments

[Mirk]

I am the Mike Taylor that is the lead author of this study. As pointed out by MaXintosh, the paper itself is freely available from the open-access journal Acta Palaeontologica Polonica, and we urge everyone who's interested to read it for themselves: we kept it short and made efforts to keep it comprehensible to intelligent non-specialists. It's at http://www.app.pan.pl/article/item/app54-213.html

Also, if the article pointed to here is Slashdotted, there is A LOT of other media coverage out there, including a TV interview, seven radio interviews, at least 25 online news sources and at least 14 blogs. Handily, we've linked them all from a page on our own blog, which you can find at http://svpow.wordpress.com/papers-by-sv-powsketeers/taylor-et-al-2009-on-neck-posture/

And maybe best, that blog -- Sauropod Vertebra Picture of the Week -- now has a sequence of seven posts explaining the research in more detail: these too are linked from the page I mentioned, and I think many Slashdotters will find them interesting.

To respond to a couple of specific points that have been raised in the comments here:

1. TinBromide though we compared only with giraffes, but in fact we compared with LOTS of animals, including birds, crocs, lizards, turtles, mammals and amphibians. The result were compellingly uniform. Similarly, MaXintosh wrote that "the authors (of the paper, not TFA) hedge their bets heavily by saying that IF sauropods are directly comparable to extant taxa". Well, sort of: we did rather nail our colours to the mast when we wrote "Can the habitual posture of extant amniotes be expected to apply to sauropods? Phylogenetic bracketing strongly supports this hypothesis as the neck posture described by Vidal et al. (1986) is found in both Aves and Crocodylia, the nearest extant outgroups of Sauropoda, as well as in the increasingly remote outgroups Squamata, Testudines and Lissamphibia."

2. eldavojohn asked "Why are we arguing over which position was the default when it's entirely possible that they utilized both positions" and noted that "There's plenty of pictures on Wikipedia [wikipedia.org] of the animals depicted both ways." It's true, of course, that animals can and do adopt different postures at different times: we make the point in the paper that sauropods had to be able to get their heads down low in order to drink, and could therefore pass through all intermediate postures. What we're talking about here is HABITUAL posture -- they way they spent their time when not actively doing something different. Geese can reach the ground, but they don't spend their lives that way.

3. A few people mentioned the problem of pumping blood up a high neck to the brain. We can't say too much about this at the moment as we're working on a paper on this subject and don't want to scoop ourselves. However, we do have good reason to think that the blood-pressure problem is not so severe as it's been depicted in Roger Seymour's work (going back as far as 1976, so we're well aware of it!) Sorry if that sounds evasive: hopefully we'll have a more convincing response for you within a year or so.

4. Finally, we want to be clear that we don't think our paper ends the debate. If anything, it re-opens it, as horizontal-to-dropping sauropod necks have been orthodox for the last decade or so. There's more work to do (but we're on the case!)

That's all for now -- hope it helps. If you have any more questions, you're welcome to ask, and we'll do our best to answer. The best place to do is probably over on Sauropod Vertebra Picture of the Week, as I and my co-authors each check that several times a day. http://svpow.wordpress.com/