Long-necked dinos didn't reach for the skies
March 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 blood pressure 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 neck 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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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
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
It would be easier to support a floating neck but still be able to reach the bottom of the lake.
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.
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.
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...
Yes, unless you weigh multiple tons. Then it seems like a good way to conserve energy.
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
And craning the neck horizontally, looking for the Smarties that were dropped on the floor!