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

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

[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

[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

[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

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: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.

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/