*Zaccheus* on 17/10/2007 at 12:07
That would help the legs but I don't think it would help the heart and lungs (though I'm really only guessing here).
Sinister_Evil on 17/10/2007 at 13:12
@Vivian
again i cant understand what exactly a muscles cross-section is. a cross-section is an intersection of a 3d object with a plane. so were exactly do you cut that object? for example a 3d ellipsis cut by a plane parallel to its long axis would produce a 2d ellipsis while cutting perpendicular to its long axis would produce a circle.
anyway.
about the tail thing are you talking about the ankys or the sauropod tail?
an ankys tail as said is a lot shorter and seems allot more powerful so dont imagine it having a really hard time swinging it. and due to the club at its end it wouldnt need that much strengh in its swing anyway. and i personally think that the anky didnt stay still an move its tail rather he rotated his whole body following the swing much like Chucks roundhouse kick. plus that would take off some of the stress on the tail while stopping since it would stop in a whole circle an not on a swing giving it time to de-accelerate smoothly.
the sauropod tail on the other hand being very long etc would need an incredible amount of strength to swing it but the "defencive tail" theory does not support a club like use rather a whip like use. a small jerky movement of the tails base would result in a fast motion of the thin end bit of the tail much like a small wrist movement whips the erm.. whip. now on the stress side i dont imagine a whipping motion exerting enough force (so an equal force exerted on the tail) as to inflict injuries while the whip slash would always hurt the enemy.
p.s. i just read in a previous post that you are a RL paleontologist. thats uber cool. i too wanted to follow that path but alas i followed the dark path of potential money making (and got lost in the process so i actually ended up on an even different path). :weird:
Hewer on 17/10/2007 at 15:06
Quote Posted by Spaztick
I don't suppose it could've been amphibious or lived in the water? I'll tell the truth I haven't actually read the whole article, I just skimmed it, but it seems like a lot of the talk here suggests it has the skeletal structure of a land animal, but maybe it spent most or all of its time in water.
When I was a kid that was an idea that was tossed around. I've got books with pictures of sauropods in the water with only their heads sticking out. They've got nostrils on the top of their head- so the long neck was like a giant snorkel, right?
I don't know all the numbers- Vivian could probably give you an educated guess- but the water pressure on the body that deep would prevent them from breathing.
Quote from Wikipedia: "Brachiosaurus attained 25 metres (82 feet) in length and was probably able to raise its head about 13 metres (42 ft) above ground level."
Again, I don't know the numbers, but 13 meters down is a lot of water pressure.
Quote Posted by Sinister_Evil;
p.s. i just read in a previous post that you are a RL paleontologist. thats uber cool. i too wanted to follow that path but alas i followed the dark path of potential money making (and got lost in the process so i actually ended up on an even different path).
Me too. I realized that I probably wouldn't be able to sustain my interest through all the technical stuff and hard work. So I opted to keep my interest through National Geographic and Discover magazines. I know Vivian is probably rolling his eyes at that.
Zygoptera on 17/10/2007 at 22:06
Quote Posted by *Zaccheus*
Another excellent point. I remember reading about the maximum length of a diver's snorkel. Giraffes must have huge lungs!
That isn't as big an issue for dinosaurs though- as Vivian mentioned previously there's a fair bit of evidence that dinosaurs had a bird like ventilation system (or
perhaps more correctly, birds have a dinosaur like ventilation system) rather than a mammalian style one. Without going into specifics too far, the avian system has unidirectional flow with very little 'dead air' compared to the mammalian one, which has a considerable amount because of its bidirectional (tidal) system. The avian system is thus more efficient than the mammalian one, and would, theoretically at least, allow for greater animal volume than a mammalian system under otherwise similar circumstances.
Vivian on 22/10/2007 at 15:31
Quote Posted by Sinister_Evil
@Vivian
again i cant understand what exactly a muscles cross-section is. a cross-section is an intersection of a 3d object with a plane. so were exactly do you cut that object? for example a 3d ellipsis cut by a plane parallel to its long axis would produce a 2d ellipsis while cutting perpendicular to its long axis would produce a circle.
anyway.
Force produced by muscle fibres is orientated along the long-axis of the fibre, so a cross-section perpendicular to that (transverse, in a parralell fibred muscle) gives you the area of active fibres, and hence a measure of the force. Because of X-section vs. volume scaling, you can't get very big with parralell fibred muscles before they start to get impractically massive. What you can do is play around with muscle architecture to increase the ratio of your perpendicular-to-fibre-long-axis cross section (generally called the physiological cross-sectional area, or
PCSA) to your muscle volume by sticking the fibres into a central tendon at an oblique angle - as in a pennate muscle.
BUT - you have then changed how your muscle works - it's now pulling on a stretchy thing (tendon) and because the fibres are oblique to the desired direction of force application they have a higher mechanical advantage but cannot produce as big a range of motion - I.E they better at providing FORCE per unit of mass, but worse at providing POWER. So if you are forced into having more and more pennate muscles because you're so fucking big and need the force to support yourself, you start to get into problems of developing novel ways to actually power your legs because you don't have many muscles capable of producing a nice range of contraction.
NB - this is theory and is in the process of being investigated. I have a friend who is working on muscle architecture in elephants, so we'll have to wait and see what she says about it.
Quote Posted by Sinister_Evil
about the tail thing are you talking about the ankys or the sauropod tail?
an ankys tail as said is a lot shorter and seems allot more powerful so dont imagine it having a really hard time swinging it. and due to the club at its end it wouldnt need that much strengh in its swing anyway. and i personally think that the anky didnt stay still an move its tail rather he rotated his whole body following the swing much like Chucks roundhouse kick. plus that would take off some of the stress on the tail while stopping since it would stop in a whole circle an not on a swing giving it time to de-accelerate smoothly.
the sauropod tail on the other hand being very long etc would need an incredible amount of strength to swing it but the "defencive tail" theory does not support a club like use rather a whip like use. a small jerky movement of the tails base would result in a fast motion of the thin end bit of the tail much like a small wrist movement whips the erm.. whip. now on the stress side i dont imagine a whipping motion exerting enough force (so an equal force exerted on the tail) as to inflict injuries while the whip slash would always hurt the enemy.
Um... I don't want to sound rude but:
A) are you really suggesting ankylosaurs span round, end-for-end, to deliver a blow with their tail? Have you been reading GON?
Big weight on end of tail = high rotational inertia, and I really don't think they could 'charge up' by spinning round and round under relatively low power like you suggest. They would still have to accelerate that large mass to strike velocity in a single tail arc, so they would have to have large, (probably parrallel-fibred COMPLETE GUESS ON MY PART) muscles. The advantage of big lump on the end of the tail is it being robust, and being able to dump a large amount of kinetic energy into the target in a short space of time. You still have to put that kinetic energy in.
B) a whip tail (high velocity/low SA) would rely on penetrating a target to do it damage. Apart from the unlikely-ness of such a system, the skin of a theropod was probably pretty thick (we have no reason to suppose it wasn't) and the terminal tail vertebrae of diplodocids are famously thin and delicate, so if they were used for this purpose you would expect systematic fractures, which you don't see. Also, the 'small, jerky' movement would still have to be very high-powered if you wanted a decent amount of energy at the tip. Making supersonic booms with it to scare stuff off is more realistic, but thats still a massive inferrence.
Sinister_Evil on 23/10/2007 at 03:01
A) no i dont read GON.
im assuming as you are. and i didnt say it powered its hit by rotating. i said it assisted the hit with its body and i mainly suggested it as an absorbing factor so the force of the whip did not stress the tail to much.
B) how many fractured bones have been observed in general. the ouch-broke-leg kind not the mortaly-wounded-died-became-someones-dinner fractures. :P
i mean whats the possibility for a sauropod to actually need to fight to the point of hitting the opponent (thus fracturing the tail) in its lifetime and then whats the possibility of said sauropod getting fossilized and then found?
ps. can paleontologist determine which fractures were made in a creatures lifetime and which during the fossilization process?
ps2. thanks for explaining that cross-section thing.
Pyrian on 23/10/2007 at 03:30
Quote Posted by Sinister_Evil
ps. can paleontologist determine which fractures were made in a creatures lifetime and which during the fossilization process?
Oh, yes, easily. Bone that breaks and subsequently heals typically leaves a distinctive imprint that looks nothing like a newly shattered bone or a broken fossil. Bones that were broken in the animal's death throes might not be distinguishable, but fractures that occurred during normal life are downright hard to miss.
Vivian on 23/10/2007 at 06:34
These were heavily built animals. I think it's less of an inferrence to suggest that they just accelerated and braked their tail with the intrinsic and back muscles rather than they 'rotated their whole body like chuck'. How fast do you think a heavy, crouched quadruped like that could turn round? Can you imagine a rhino doing what you're suggesting? I mean, you are right - ornithischian dinosaurs are well extinct and could have all sorts of wierd attributes, but unless you've got a very good reason to suspect some aspect of it's behaviour you're just hand-waving. Which while fun is not science, as enough people tell me about palaeontology anyway.
edit - just spoke to aforementioned friend working on elephants. Aparently, they reduce all of their more distal limb muscles, hold their legs straighter and thicken their bones, which saves a bit of weight and allows them to maintain their large, heavy power-producing proximal parallel-fibred muscles. In terms of what that means for sauropods... I dunno. If it's a trend, maybe they were pretty much just bone and passive tendon-y stuff in the lower leg to allow them to have massive parallel muscle in the upper leg.
Sinister_Evil on 23/10/2007 at 14:31
rhinos are pretty fast when they want. they have been known to chase jeeps and stuff. though to answer your question no i havent seen a rhino displaying such behavior. then again the rhino does not have to.
any spin of the body would be aided by the initial momentum of the tails swing. plus animals are known to exhibit bursts of speed and power for short periods of time such as rhinos chasing jeeps, crocodiles chasing its prey (on land) or jumping high out of the water.
Vivian on 23/10/2007 at 15:25
Yes they do, but they generally don't do it by rotating their entire body. They do it with white muscle in crocs and with um.. magic.. in rhinos (rhinos are too agile for something that big. They're weird. But importantly, they don't spin) Maybe some arthropods spin around to hit things or stop hitting things. Wasn't that what you were suggesting ankylosaurs had to do because they didn't have a massive neck? Which sauropods have to have because they hit things with their tail?
You know what I think? balance and vibration damping. You have a long goddamn neck for browsing (seems odd, but makes most sense of available options). Don't neccesarily need a long tail to balance that neck (look at giraffe), do need bit of a tail to house the caudofemoralis muscle ((
http://links.jstor.org/sici?sici=0094-8373(199021)16%3A2%3C170%3ACMATEO%3E2.0.CO%3B2-S) main hindleg retractor), but if you have a neck that long and are walking around you are damn well going to get some kind of vibration up and down it. Perhaps having a long tail helps to tune a nice standing wave, so that you can keep your head stationary while the rest of your spinal column wiggles. Any takers?
