Long-necked dinos didn't reach for the skies

Mar 31, 2009
A handout image obtained from the University of Portsmouth in 2008 shows an artist's impression of a sauropod. A fondly-held belief about long-necked sauropods, the giant four-footed dinosaurs beloved of monster movies and children, is most probably untrue, a dino expert said on Wednesday.

A fondly-held belief about long-necked sauropods, the giant four-footed dinosaurs beloved of monster movies and children, is most probably untrue, a dino expert said on Wednesday.

At the zenith of the dinosaurs' reign, some sauropods evolved necks of extraordinary length -- more than nine metres (29.25 feet) in the case of the Mamenchisaurus, a titan of the Late Jurassic period around 150 million years ago.

Prevailing wisdom has it that these leviathans used their necks like giraffes today. They reached up high into the trees, munching leisurely on forest canopy that was out of reach for rival herbivores.

Not so, says a paper appearing in Biology Letters, a journal published by Britain's prestigious Royal Society.

It argues that giant sauropods most probably preferred to feed horizontally, rather than vertically, on the grounds of energy cost.

Australian evolutionary biologist Roger Seymour did a simulation of how much a gigantic sauropod would need in order to place its head vertically.

He then calculated how much energy the creature would require in order to pump around blood at this high pressure.

"It would have required the animal to expend approximately half of its energy intake just to circulate the blood," says Seymour.

"A vertical would have required a high systemic arterial blood pressure. It is therefore energetically more feasible to have used a more or less horizontal neck to enable wide browsing while keeping blood pressure low."

Other dino specialists have likewise argued that long-necked sauropods were unlikely to have had a heart that was big enough to enable it to feed vertically for much of the time.

The Barosaurus -- whose neck put it in the same category of length as the Mamenchisaurus -- would have needed a heart weighing five percent of its bodyweight to pump blood to neck muscles and brain for craning upwards, according to a 2000 study.

(c) 2009 AFP

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mforbes21
5 / 5 (5) Mar 31, 2009
Has anyone performed an analysis to see how much energy it requires to hold a neck of this length (plus the head) at a horizontal position, vs. how much it would require to keep it vertical?

I remember somewhat non-fondly being in basic training, and as part of being 'cranked' (forced exercise), to carry my demilitarized 11 pound rifle above my head for extended periods, while running in place. As awful as this was (although granting that I got in to the best shape I've ever been in my life in a miraculously short period of time), it was a vast improvement on the even worse punishment: holding my rifle in front of me, with arms at full extension, while running in place.

I'm curious to know, based on the skeletal structures of the long-necked dinos, and how their muscles attached to the skeleton, which position would require more energy for the dinos.

-Mike
Yarking_Dawg
3.7 / 5 (3) Mar 31, 2009
Mike, A horizontal neck would take little to no energy to hold in place.

Best evidence is that tendons would have carried the weight like cables holding the weight of neck counter-balanced against the weight of the tail.

DVB
Arikin
5 / 5 (4) Apr 01, 2009
Wait. I always thought sauropods spent most of their time in the water. Feeding like hippos.

It would be easier to support a floating neck but still be able to reach the bottom of the lake.
Szkeptik
4.2 / 5 (6) Apr 01, 2009
Ok, then why the hell have a long neck at all?If you can't reach up, what good is it? Predators like to go for the neck, why give them so many of it?
Mercury_01
4 / 5 (8) Apr 01, 2009
Yeah, these things were juggernauts. All of them. I don't think its correct to assume that they did not have enough energy to use their bodies to their fullest potential. Perhaps Roger Seymour is a fat lazy bastard without any regard for life, and he wonders how other people can walk two blocks to the store. He probably goes around with his head bent over and does his research from a chaise lounge, being tended to by dainty servants.
Husky
1 / 5 (1) Apr 01, 2009
I guess we humans have to grow back our tail prior to millitary exercise ;-)
LariAnn
3.3 / 5 (3) Apr 01, 2009
If the idea is that sauropods did not eat with neck extended vertically, then how in the heck would evolution have resulted in such long necks? This would seen a good situation where "I don't know" is the right answer. IMHO, the idea that they fed horizontally doesn't support any evolutionary concept requiring the development of a long neck.
smiffy
2.3 / 5 (3) Apr 01, 2009
Ok, then why the hell have a long neck at all?If you can't reach up, what good is it? Predators like to go for the neck, why give them so many of it?
If the idea is that sauropods did not eat with neck extended vertically, then how in the heck would evolution have resulted in such long necks?

Maybe the idea was to frustrate those predators' targetting of the neck area - by evolving the height of the neck above the level which most predators can reach. Having done that however, there remains a problem with feeding. In order to reach the ground for ground-based vegetation and for drinking you're going to need a long neck (or develop a substitute neck like the elephant's trunk). The neck need never be lifted much above shoulder height.
docknowledge
5 / 5 (2) Apr 01, 2009
Blood pressure only has to be partly sustained if dinos were to make a quick "reach and snatch". If they threw their heads quickly enough maybe there would be no pressure loss at all. (Notice that Seymour apparently wrote "prefers" horizontal.)
DozerIAm
5 / 5 (4) Apr 01, 2009
I would imagine that holding the neck horizontal requires less blood pressure but far more muscle exertion, where as holding it vertically required more blood pressure but far less muscle exertion - the caveats being (1) there would be a whole lot of stabilizing going on in the vertical position, and (2) since we only have fossil record we don't know anything about the vascular system, these critter may well have had some system for managing this arrangement - one way valves, fr'instance?
barakn
2.3 / 5 (7) Apr 01, 2009
There's a lot of b.s. being thrown around here.

Yarking Dawg is correct about the amount of energy for a horizontal neck, and DozerIAm is not.

Arikin- the idea that the sauropods were swamp beasts arises from an early and incorrect belief that they were too heavy to support their weight on dry land.

Docknowlege's "reach and snatch" maneuver would cause a case of orthostatic hypotension that would leave the animal's brain without oxygen at the most crucial moment - in mid snatch. While whipping it's head up into a tree to eat some leaves it's liable to miss the food and poke its eye out on a tree branch.

The long neck is all about obtaining large amounts of food without needing to move the body much. The linear feet swept out by the head and neck is proportional to the length of the neck - assuming the neck only bends where it meets the body. If we model a neck as being able to curve, the reachable area will be some power of the neck length l, i.e. l^x, with x being somewhere between 1 and 2. A neck twice as long means two to four times as much food within easy reach.
Sophos
3.3 / 5 (3) Apr 01, 2009
How can a horizontal neck require little or no energy? - remember basic physics r x F ? there is a lot more torque at the base of the neck in the horizontal position. This is why you see large cranes stored upright. Otherwise they are too easily damaged
QubitTamer
4.3 / 5 (4) Apr 01, 2009
Assuming a vascular structure identical to existing vertebrates seems over-reaching the empirical evidence at hand. There is no evidence that these creatures would not have used their anatomy in an efficient reach-pull-drop-chew cycle, thus obviating the need to pump blood for long periods with the head elevated.

Empirical evidence abounds however for the concept that creatures use their anatomic structure efficiently for the most part. There is no reason to believe in a black and white scenario of horizontal or vertical feeding...
Mercury_01
3.7 / 5 (3) Apr 01, 2009
I agree, qbit. And for all we know, these animals slithered their heads back and forth constantly like Medusa's hair, while spinning pirouettes to get the blood out to their heads before a feeding session. Plus they probably had sweet lasers.
smiffy
5 / 5 (3) Apr 02, 2009
A neck twice as long means two to four times as much food within easy reach.
Why go to all the trouble of evolving a long neck purely to increase easy reach of ground food when you've got legs that can do the same job? Seems perversely extravagant.
thales
4 / 5 (2) Apr 02, 2009
A neck twice as long means two to four times as much food within easy reach.
Why go to all the trouble of evolving a long neck purely to increase easy reach of ground food when you've got legs that can do the same job? Seems perversely extravagant.

Yes, unless you weigh multiple tons. Then it seems like a good way to conserve energy.
smiffy
4.5 / 5 (2) Apr 03, 2009
Yes, unless you weigh multiple tons. Then it seems like a good way to conserve energy.
Yes it does. But by the time the beast gets to weigh 'multiple' tons with a sauropod's body type(front legs longer, or at least equal to the hind legs) it would have attained a height that necessitated a long neck for drinking purposes. You only have to watch a giraffe drinking to see that it needs all its long neck to get down to the water's surface - and that's with its front legs splayed. An elephant for instance would need a neck as long as a giraffe's if it didn't have its trunk. (It wouldn't be a good idea for an elephant to kneel down at the edge of a waterhole for fear of getting stuck in the mud)

So I'm guessing that the long neck was already in place by the time the sauropod became big. Energy conservation might then come into play and be reponsible for the final extension to the very long neck you see in the giant sauropods.
thales
4.7 / 5 (3) Apr 03, 2009
So I'm guessing that the long neck was already in place by the time the sauropod became big. Energy conservation might then come into play and be reponsible for the final extension to the very long neck you see in the giant sauropods.

Well, either the neck came first or the size came first. Very often a feature (not a bug!) evolves to solve one problem, and then gets repurposed for another problem down the road.

http://en.wikiped...aptation
VOR
3.7 / 5 (3) Apr 04, 2009
I think they are making assumptions that could very well be 'reaching'. 'experts' will never learn and continue to make statements that are just guesses. I agree with qubittamer. and there are other vascular 'tricks' that could be employed to allow for brief vertical positions without need for extra-massive heart, such as various constrictions and 'check valves'. That's how humans do it. I have a normal heart size but experience orthostatic hypotension if I stand still for a few minutes. It has to do with lack of adequate vascular control through various chemical signals.
UncleDave
1 / 5 (1) Apr 05, 2009
Yeah, these things were juggernauts. All of them. I don't think its correct to assume that they did not have enough energy to use their bodies to their fullest potential. Perhaps Roger Seymour is a fat lazy bastard without any regard for life, and he wonders how other people can walk two blocks to the store. He probably goes around with his head bent over and does his research from a chaise lounge, being tended to by dainty servants.

And craning the neck horizontally, looking for the Smarties that were dropped on the floor!
el_gramador
not rated yet Apr 06, 2009
It might just be a situation of trying to find out the ideal position, or reassert an already known hypothesis. That being, sauropods hold their necks up in neither vertical or horizontal direction at any one time. If anything they would take their time moving around like giant cranes and probably keep their necks where the forces are most balanced and comfortable, i.e. at a balance of horizontal and diagonal. Along with the fact that not all food would have been so high as to be entirely vertical. If food is set along a range of heights, then it isn't very likely for the head to have required much strain in going for any set height. If it was too high or too low, the animal wouldn't go after the food. Otherwise, it would die from too much tension or not enough blood. Evolution doesn't make things stupid, it makes them able.
Royale
not rated yet Apr 06, 2009
has anyone read "Jurassic Park"? Michael Crichton brought this up years ago. It's just coming up in the news now?