The Impossible Size of Dinosaurs

Originally posted by Arbitrageur
Some dinosaurs had another trick that allowed them to eventually evolve into birds: hollow bones. But some huge dinosaurs may have had hollow bones too:

Would a hollow bone be able to support such a massive weight without dramaticly different conditions, such as (thick) atmospheric buoyancy, or lesser gravity?
-E-

Originally posted by MysterE

Originally posted by Arbitrageur
Some dinosaurs had another trick that allowed them to eventually evolve into birds: hollow bones. But some huge dinosaurs may have had hollow bones too:

Would a hollow bone be able to support such a massive weight without dramaticly different conditions, such as (thick) atmospheric buoyancy, or lesser gravity?
-E-

Hollow bones can be extremely strong, as they are normally not completely hollow but have something similar to a "honeycomb" structure. So instead of having one huge hollow area inside which could make it weak, it's actually quite strong for its weight.

So I expect the answer is yes.

reply to post by Arbitrageur


reply to post by MysterE



One theory is that many of the larger herbivorous were semi-aquatic. Or lake and river dwellers. Which would have off set the weight issue. Again we have no real way to prove or disprove at this point.

Just more speculation.

Not only that but if the hollow bone theory is true then we need to consider that the present day "Bird" came from the Dinosaur not they other way around so it's prodigy would not have the same type of bone structure but the "Evolutionary outcome" Therefor would not be anything like what was it's Genesis.


[edit on 8-12-2009 by SLAYER69]

Originally posted by SLAYER69

Originally posted by MysterE
reply to post by SLAYER69

 

To add to your post, there is the question of how the Brachiosaurus was able to supply blood to it's head (being so much higher then where the heart typipcally is)-

Well unfortunately we are bound by present day conditions. The closest thing we can compare them to is the giraffe.

Yes the Giraffe solves the problem, doesn't it?

The fact that it does means there are solutions to some of these seemingly insoluble problems. Whether the dinosaurs implemented the same solution as the giraffe I don't know, but I don't think the tail is a major factor in the problem associated with a pump like the heart having to pump blood to a head which is much higher.

My guess would be that the dinosaurs had a system similar to the giraffe to overcome this problem, and it is a real biomechanics engineering problem:

'Supercharged' heart pumps blood up a giraffe's neck

Originally posted by Arbitrageur

 

Yes the Giraffe solves the problem, doesn't it?

It certianly adds credance to the possibility. From a previously linked article.

Yet the giraffe’s greatest cardiovascular problem is having a strong enough heart to lift blood up to its brain. To produce the necessary blood pressure the giraffe’s heart is a huge muscle with walls up to three inches (eight cm) thick and weighing 25 pounds (11 kg). But even more impressive is that the giraffe’s resting heart rate is 65 beats per minute. This is about twice what is expected for an animal of its weight. The giraffe’s massive ‘revved up’ heart produces the 300 / 180 mm Hg blood pressure needed for the blood to reach the giraffe’s head. Giraffes have a relatively short lifespan of only 20 years and are prone to heart attacks as a consequence of their cardiovascular adaptations.

Yet if the giraffe is an amazing animal in overcoming all of these cardiovascular problems to achieve its height, what should think of the Brachiosaurus that stood at a height of 13 meters? While the giraffe’s head is 2.5 to 3.0 m above its heart, the brachiosaurs’ head was 8.0 to 9.5 m above its heart. As the variety of unlikely proposals show, scientists are baffled as to how to explain this.

-E-

Originally posted by Arbitrageur
I don't know, but I don't think the tail is a major factor in the problem associated with a pump like the heart having to pump blood to a head which is much higher.

I respectfully disagree.

Every movie/animation we have seen always shows the tail as either a weapon of some sort or it just swishes from side to side. However why wouldn't it also act like some sort of hand pump in coordination with it's heart?

With an up and down motion?
[atsimg]http://files.abovetopsecret.com/images/member/e7e8087207d0.gif[/atsimg]


[edit on 8-12-2009 by SLAYER69]

Originally posted by SLAYER69
Every movie/animation we have seen always shows the tail as either a weapon of some sort or it just swishes from side to side. However why wouldn't it also act like some sort of hand pump in coordination with it's heart?

With an up and down motion?

No, If you take apart that pump you'll see the mechanism that generates that pressure inside. When you look at a heart, the pressure generating mechanism is self-contained.

The tail could have an influential effect if the tail was lifted up, then the heart would have to pump that much harder to supply both the tail and the head. But once the tail was lowered the only reason it's easier to pump blood to the head is that you don't have to pump blood to a tail which is also elevated, it's not due to any "pumping action" from the tail.

I suspect the primary purpose of the tail in many animals is balance, and in some dinosaurs it was used for defense.

Forgive me MysterE, I have not read the whole thread but, maybe the size they grew up to has something to do with the two bar theory? That would also explain why their nostrils were so small compared to the size of their bodies....

reply to post by jinx880101


A quick search couldn't find anything on the "two bar theory", care to enlighten me? I presume the term "bar" refers to the measure of atmospheric pressure, and if that is correct that the pressure was at two bar? It has been a while since my last physics class, but isn't 1 bar the current atmospheric pressure?

-E-

reply to post by jinx880101


What is the two bar theory, if you don't mind me asking? haven't heard about it yet and google didn't produce answers.

You can learn something new every day

If you mean 2bar of air pressure i don't think it would cut it as a solution. It would help the circulatory problem but not the mass/muscle/bone problem.

Originally posted by Arbitrageur
The tail could have an influential effect if the tail was lifted up, then the heart would have to pump that much harder to supply both the tail and the head. But once the tail was lowered the only reason it's easier to pump blood to the head is that you don't have to pump blood to a tail which is also elevated, it's not due to any "pumping action" from the tail.

Well as I have stated earlier, it's all conjecture.

i think the atmospheric pressures were different then, meaning the air was lighter, meaning dinosaurs were lighter.

Originally posted by raj9721
i think the atmospheric pressures were different then, meaning the air was lighter, meaning dinosaurs were lighter.

How on earth does atmospheric pressure correlate with gravity?

Originally posted by raj9721
i think the atmospheric pressures were different then, meaning the air was lighter, meaning dinosaurs were lighter.

I think it is quite the oposite. Think of the atmosphere as a fluid, the more dense (like water) the more you float.

-E-

reply to post by above


easy, lighter air, means anything filled with that air will be lighter. and the dinosaurs' lungs were filled with that lighter air.

how does a balloon filled with helium escape gravity when a balloon filled with normal air won't?

Originally posted by MysterE

Originally posted by raj9721
i think the atmospheric pressures were different then, meaning the air was lighter, meaning dinosaurs were lighter.

I think it is quite the oposite. Think of the atmosphere as a fluid, the more dense (like water) the more you float.

-E-

No we are both right, the more dense the atmosphere becomes the lighter an object in that atmosphere becomes.

www.soest.hawaii.edu...

[edit on 8-12-2009 by raj9721]

the reason for the difference in pressures from now until then is partially due to the decreasing of sea levels over time.

Originally posted by above

Originally posted by raj9721
i think the atmospheric pressures were different then, meaning the air was lighter, meaning dinosaurs were lighter.

How on earth does atmospheric pressure correlate with gravity?

gravity controls the weight of the air, even though gravity is relatively weak it still effects everything, even light.

reply to post by raj9721


So on the moon theres no gravity, as theres no atmosphere? Yeah right...

Gravity is caused by the mass of the object. The atmospheric lift is minimal in affecting the weight of the object.

[edit on 8-12-2009 by above]

reply to post by raj9721


If the atmosphere is as almost as light as nonexistent, then nothing will lift off evenif 99,9% of their body is filled with it because the surroundings are just as light. Come on, please do your research before trying to act smart-ish