|Ok..... This is really interesting.... BUT... we are doing the math based on the wrong assumptions again. Here, we are saying that theropods ran like birds and mammals. They ran like neither. They ran like theropods. Why is this fact usually shoved under the carpet and the couch moved over it? Never mind that we are talking about a combination of crocodilian hips coupled with an avian lower leg that no longer exists in modern animals, but you have a huge ilium that gives great leverage. You have the crocodilian pull of the tail.... The get up and go bit..... This pulls it off its mark and gets it going. The caudofemoralis... it's huge in tyrannosaurs. It's tiny in birds. Bird locomotion is thus all in the knees. And mammals? Mammals have both the knee as well as the lumbar. The âarch-range of motion' of the femur is increased by the lumbar region as it acts as a sort of spring. The shoulder region in mammals also acts as their spring. This âarch-range of motion' is rare in bird femurs most of the time in the first place, and never seen aided by a moving lumbar region because their dorsal vertabrae are fused. We all know this. In birds, their spring is in the cnemial tendons. Only when the pectoral region grows larger to help power the flight muscles do we see the increased lower limbs in birds and this is most likely because of weight. With all the weight forwards the body in birds, they needed to move the gut back to displace some weight. This spreading of both the distal symphysis of the ischia and pubis, as well as flare in the ilium in a lateral manner of birds, put the femur at a disadvantage mechanically. So, the only way birds could make up for this was to select for moving the motion of the femur that was once a prime mover of the rear limb to the knee. They did this by elongating the tibia as well as the metatarsal elements. In this way it helped also to balance the animal as well by being able to keep its feet further forward when standing... I'm going offf on a tangent....... Someone smack me...
So anyway, non-avian theropods use the entire leg...... They use their femur to make up for the difference. Their caudofemoralis. Leg length.... Foot prints.... Everything shows this. Yes, the study definitely showed that they walked fast.... Tyrannosaurs were speed walkers... Works for me... BUT... they still could also take off from the ground as well... They still had a "ballistic phase". It's all the knee cartilage and tendon spring. In birds, its the cnemial tendons. In theropods, you have the cnemial tendons and lots of cartilage as well. And by the way, crocodilians are slow??? I guess the footage of "galloping" crocodiles must be more of that Lucasfilm movie magic....
Face it... Bumble bees would not have been able to fly if we had not seen them do so. That made the people go back over and over to get their math right so they didn't have to say "I did the math and they can't do it."
It's like a friend of mine says... How about the vaulted palate in birds? In most animals, we would have thought anything without a secondary palate was an ectotherm. But, birds do not have in most cases anything like a secondary palate. So, if we had only theropods, a lack of the secondary palate would have been proof positive that they were cold blooded. It would have been wrong, yet proof positive.
Things work like this..... As I see it, if we do not have an example these days to go by, and we cannot make it work with clever math, then, it ain't so...... You know, even when we still cannot figure out how in the hell whales can dive so deep...... And we are only now starting to maybe figure how tuna swim so fast. All the math says they cannot swim as fast as they do.... If they were extinct, that case would have been closed. To make this even funnier, here we are comparing theropods to animals that look nothing like them and drawing conclusions for them based on the math we use on these animals that look nothing like them. Ok...... Sure..... Yeah.... crocs that are alive today look so much like theropods.... Yup... that is soooooo true. ::rolling eyes:: And chickens...... closer to theropods, but still greatly changed. I mean face it.... Chickens are built for chicken sized lives.... Not theropods..... as in mega theropods. Chicken femurs articulate with the tibia different then tyrannosaur femurs.... Chicken femurs move in the vertical. Theropod femurs more more in the horizontal. The locomotion is completely different in the two animals. Tyrannosaurus are very close in build to ornithomimids. I mean, they look the same but have more robust bones. Maybe those are the animals we should be comparing tyrannosaurs too???? Paul's 1988 book comes to mind.
After reading the paper, (I'll send it to anyone who doesn't want to wait for their issue to arrive at the house) as far as I can tell, this study left out the elasticity of cartilage and tendons. I look at it this way... A friend pointed out to me that whales could not swim without their skin. If it did not bounce back, all their energy would be lost at a huge rate. The skin is very tight.. made up of a web stock of connective tissue. When the whale makes a tail stroke, its power is not lost. It bounces back and is saved. This is one way that an animal that huge with the metabolic make-up of the average cow can swim so damn fast. Birds use their tendons and cartilage like whales use their skin. It's like a pogo stick effect. They tighten the tendons and sort of bounce. It's more of a falling forwards and just holding themselves from falling over. Bounce.... bounce...... bounce.... If this is not put into calculations correctly, you are completely lost. You loose all your energy at a very fast rate, and ya blame it on the lack of muscles. :-) Poor math is always there to help people prove that an animal cannot do what it does 24 hours a day.
Fr = (velocity)^2/(hip height x g)..... As far as I am concerned, the formula is really no good for theropods. It is again, based on mammals with their lumbar region moving and birds with motion mostly from the knee. Theropods need to be measured as living animals to see if they actually fit the formula. I mean, most of the mammals as well as birds that run go from the knee down. Theropods do not in any way fit this. They are femur and knee. And what about measuring how the caudofemoralis fits in, as well as how the femur works without the flaring of the ilia? And what about how the muscles of the pubic bone fit in as well? In birds, they are separated distally, and are thus no good for moving the femur at all. But in theropods like the rex? Talk about having a nuclear generator. All of these things have to be added in. Tail muscles.... Iliac muscles... Pubic muscles... All going to the femur. Then in comes the flexed knee. The monsterous cnemial crest on the tibia. The flexible ankle. Then comes in the bouncy tendons as well as cartilage.
Looks like I'm going to have to break out the Ouija board and ask Capt. Howdy for the location of a _Tyrannosaurus rex_ trackway that will show it's stride and maybe even its speed. In my humble opinion, that's the best we can hope for.