Identical Cousins?
Posted on 02/27/2002 10:29:03 AM PST by RoughDobermann
Edited on 04/29/2004 2:00:10 AM PDT by Jim Robinson. [history]
STANFORD, California (CNN) -- New models of the leg muscles of Tyrannosaurus Rex suggest that a real T-Rex might not have passed the screen test for "Jurassic Park." Stanford University researchers writing in the British journal Nature this week suggest that a T-Rex could not have been able to run as fast as the one in the movie -- and might not have been able to run at all.
(Excerpt) Read more at cnn.com ...
But, is this a linear path or exponential? if the percentages are the same - how fast can an osterich run and what percentage of it's total body weight is leg muscle?
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Identical Cousins?
T-Rex: Scientists couldn't move fast
Muahahhahahah
The pictures showing men hunting deer with javelins are actually poets exxercising their license to depict what's gonna' happen to 'em when they get home.
The second modus operendi to look at is that of wild dogs and wolves, who compensate for lacking weaponry other than teeth by hunting in packs; it's a bit much to picture tyranosaurs hunting in packs.
The third method of operation may actually be the one primarily used by tyranosaurs, and that is the method favored by storks and a number of wading birds. This method depends on the fact that most prey animals don't spend a whole lot of time looking upwards for eyes and teeth; basically, you just stand there and wait for something short and stupid (a democrat or an evolutionist perhaps)to walk by, and then you snap it up. Teeth and patience are all which is required.
That was not the claim. The claim is that a bumble bee cannot fly using stiff wings. Bumble bee wings are flexible. One can also show that a bumble bee cannot glide. (The true stories are actually more interesting.)
IIRC, the amount a force a muscle can exert goes up proportionaly with its cross-sectional area, but the weight goes up by volume- an animal four times as big would have muscles twice as strong, but would weigh 64 times as much. I think.
A current topic in paleontology that has received much popular press is the question of whether T.rex (or other Tyrannosauridae in general) were predators or scavengers. Let's explore this issue.
Paleontologist Jack Horner of the Museum of the Rockies (Bozeman, MT) has proposed that T.rex could not have been a predator. His arguments against predation include its small eyes (needed to see prey), small arms (needed to hold prey), huge legs (meaning slow speed) and that there is no evidence for predation — bones have been found with tyrannosaur teeth embedded in them or scratched by them, but so far no study has shown that tyrannosaurs killed other dinosaurs for food (a bone showing tyrannosaur tooth marks that had healed would be strong evidence for predation).
His evidence supporting scavenging include its large olfactory lobes (part of the brain used for smell), and that its legs were built for walking long distances (the thigh was about the size of the calf, as in humans). Vultures have large olfactory lobes and are good at soaring to cover long distances.
There are arguments against scavenging. Most large living predators (such as lions and hyenas) do scavenge meat happily when it is available, but most do prefer fresh meat. Dr. Horner argues that its arms were too weak to grab prey, but sharks, wolves, snakes, lizards and even many birds are successful predators without using their forelimbs (if any). Whether T.rex was a slow animal is tough to tell, as our dinosaur speeds page will tell you.
What is the public to think of all this? It is suggested that you make up your own mind; the fact is that reconstructing the behavior of extinct animals is difficult, especially when there are no close modern relatives with which to compare them. Tyrannosaurs may have been scavengers, predators or both; Dr. Horner is merely presenting an opposing argument that shows that we are not yet 100% sure what ecological niche the great tyrannosaurs filled.
don't think "they" ever said they had proved a bee couldn't fly, just that the model they were using couldn't account for it- more recently, IIRC, "they" have figured out that flapping insects use their wings to create vortices, and sort of "surf" on them, as opposed to birds, which apprently use the reaction force of the air their wings accelerate to provide lift/thrust. Then again, I may have that entirely wrong.
We know that dinosaurs moved; they were vertebrates, and we have their trackways (sequences of footprints) preserved in certain sediments as fossils. One popular question is how fast did they move? Did some of them run as fast as the modern cheetah? Most scientists involved in the investigation of dinosaur locomotion think not. We have several lines of evidence that can help us estimate how dinosaurs could move.
One line of evidence is the information given to us by those trackways. Two samples of the UCMP's large collection of theropod dinosaur footprints are shown above; note the amazing similarity to the tracks of birds on a beach or muddy ground. We don't know of any giant birds that were around in the Mesozoic era, and no other vertebrates had feet quite like those of theropod dinosaurs, so we can be confident that these footprints were made by the carnivorous dinosaurs.
A good sequence of preserved footprints (called a trackway) can be extrapolated to give a rough estimate of how fast that particular animal was traveling at that moment. This method uses simple equations based on the distance between footfalls and the size of the feet. The fastest speeds evident from dinosaur tracks (a medium-sized theropod in this case) are about 12 meters per second (about 27 mph); a little faster than the best Olympic sprinters. Problem: It's hard to tell who made those tracks! We usually can narrow down our identification to large vs. small theropods, sauropods, or whatever. Then, knowing what sorts of those dinosaurs lived around there at the time the tracks were made, we can get ideas of who might have made those tracks. Then we have a shaky guess as to what dinosaur was moving at what speed at that instant. The obvious problem: "At that instant" is the key phrase; most animals are not running at top speed all of the time, especially when on soft ground, where tracks are most likely to be made. So we just have a glimpse into a brief moment in time; not a thorough analysis of dinosaur behavior. Good trackways are quite rare, too. But trackways are what we have to work with, so paleontologists must make do with that evidence.
The morphology (shape and structure, or anatomy) of dinosaurs may be a more useful tool, but it is much more difficult to use properly. We can reconstruct dinosaur skeletons to figure out how the bones were connected, and make predictions about their functional morphology (how their bodies moved and worked) from muscle scars and other anatomical features. We have done that, and learned long ago that dinosaurs stood erect (like birds and most mammals); they did not keep their legs sprawling out to the side of their body like most lizards and salamanders do. Also, from the trackways of dinosaurs, we know that they rarely dragged their tail on the ground -- normally, their vertebral column was oriented roughly horizontally with respect to the ground. So, mammals and birds are probably better models for understanding dinosaur locomotion than lizards are (but all are useful to some degree, and all are limited in their usefulness). Now it gets tricky!
There are at least two ways we can go from here: one is to simply compare dinosaurs with extant (living) animals whose motion we understand better, and make assumptions based on the similarities and differences between the two. This can be called the morphological paradigm. The hadrosaurs and theropods had many members whose skeletal structure was similar to that of some modern cursors (animals that are good runners, like horses and ostriches): long legs, digitigrade stance (walking on one's toes), and so on. So we might think that some of those dinosaurs were “cursorial,” or specialized for locomotion, but because their locomotory features are not as specialized as those of many of the faster extant runners, we think that it is unlikely that any non-avian dinosaurs ran incredibly fast. Similarly, many sauropods, thyreophorans (armored dinosaurs), and ceratopsians were similar to modern graviportal (non-cursorial, heavily-built) animals like elephants, so paleontologists think that such large dinosaurs were less speedy. In general, big land animals use less strenous activities than their smaller relatives.
A second direction we can take is more conclusive, but much harder. We can use the laws of physics and apply them to our dinosaurs; this is called biomechanics. We can "reconstruct" a dinosaur's muscles (using the musculature of the dinosaur's closest living relatives -- the crocodilians and birds -- as guides), estimate its weight, and apply established engineering principles to figure out how fast that particular dinosaur could move if it wanted to. Or so we think. The problem is that it is very hard to do this with any living animal! The difficulties are staggering when we try to do this with 65 million year old fossils (which are often incomplete). When you hear quotes about T.rex moving 40-60 mph, ask for the evidence and judge for yourself.
Let's not get into the dinos are birds controversy!
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