Sauropod Dinosaur Physics
Biological Blood Pressure Limitations and More
Giant Sauropod Dinosaurs could not have eaten leaves from the tops of tall trees. The organic cellular structure of their hearts and blood vessels could not have created nor withstood the enormous blood pressure that would have been necessary to keep the brain alive and functioning vertically more than about nine feet above the heart. Animal cell structures, either then or now, simply were incapable of being durable enough for the animals to survive. Even today, giraffes cannot grow to be more than about 18 feet tall, and half of that is due to long legs. A heart and circulatory system made of known biological cellular tissues cannot create blood pressure sufficient to pump blood more than about nine vertical feet above the heart, or bring blood back from legs and feet lower than about nine feet below it. Giraffes even have to have unique "braided" blood paths in their necks to and from the head, to reduce the danger of cerebral strokes if the head is quickly raised or lowered, to avoid bursting tiny capillaries in their brains and to minimize heart valve failures and blood vessels bursting. Male giraffes are around seventeen feet tall, with their heart about at eight or nine feet high. Giraffe hearts and circulatory systems are as sturdy as has ever been known in animals.
A number of commonly accepted assumptions about large dinosaurs are not compatible with scientific laws. For example, sauropods grazing from the tops of trees were physiologically impossible, for blood flow reasons. If any part of any dinosaur’s body ever got above eighteen feet high, blood flow would cease and cell death would be imminent. If this included the brain, lack of consciousness would quickly occur. If this resulted in a fall, a blood pressure surge would occur in the brain, with a likely fatal stroke. Since large dinosaurs seem to have lived for hundreds of years, and they existed for many millions of years, we have to believe that this rarely happened.
I first discovered this logic around 1996, and published this result. By around 1998, many of the major Museums around the world recognized this and they disassembled their "high-reaching Sauropod" displays to reassemble them with their heads and necks cantilevered horizontally in front of them.
Sauropod dinosaur fossils were only first found about 100 years ago. Until fairly recently, only a very small number of fossils had been found, and never, until VERY recently, had nearly an entire animal fossil been found. Most true scientists recognize and acknowledge that many assumptions have been necessary toward any understanding of these long lost creatures, so they accept the uncertainties of many of the characteristics that have been attributed to them.
An early dinosaur fossil researcher (Marsh) found many of the fossilized bones of a brontosaurus (in 1879, at Como Bluff), but he did not find a skull. In an unbelievably unscientific (and scientifically disgusting!) move, he found a somewhat similar skull at a considerable distance away, where no dinosaur fossils had been found, and he claimed that the skull belonged with the skeleton. (He certainly knew that was not true.) For a hundred years after that, all the display brontosaurs in Museums worldwide showed that same (wrong) skull! It has only been in the past several decades that the error (or deception) has been uncovered.
This extensive Research regarding dinosaur physiology was performed beginning April 1996. This presentation was first placed on the Internet in November 1997.
This is mentioned here for a couple reasons. (1) For as famous as dinosaurs have become, there are amazingly few substantial skeletons that have ever been found, especially before the early 1990s. A Tyrannosaurus Rex was discovered around then that was nearly complete, and it caused a huge stir among dinosaur researchers. (2) The impressive displays that draw millions of visitors to various Museums are virtually never the actual fossils. They are virtually always plaster casts of the actual found fossil bones. Worse, in some cases, the display skeletons were based on the finding of a single major bone! In one case, a thigh bone had been discovered early in the 20th Century, and a Museum staff created casts of what they ESTIMATED to be the sizes and shapes of all the other bones! In most cases, they used good logic in making such guesses, but technically, they were still guesses. Similarly, several years ago I walked into a retail store in Orlando, Florida that sold only dinosaur related products, because as a scientist I was naturally curious as to what they could possibly have. Hung from the ceiling, there is a huge swimming dinosaur skeleton, maybe thirty feet long, and PERFECT! I located the shop owner and asked about the validity of it, and he announced that it was THE original fossil, found in Kansas. I pointed out that I noted how perfectly identical the hundred tail vertebrae were, There were no deformations, no imperfections, no signs of wear not even one sign of any injury! At that point, I mentioned that I was somewhat knowledgeable about some dinosaurs, and that I knew for a fact that no absolutely complete skeleton of any plesiosaur-type dinosaur had ever been found. I noted that the world scientific community would want to examine what was hanging from his ceiling IF it was in fact valid. After still insisting that it was an entirely real skeleton, he finally admitted that all of the pieces were actually plaster casts, and that none of it was an actual fossil. In a couple more minutes of critical questions, he finally admitted that the discoverer of it (who was NOT a known dinosaur expert) had only actually found a few fossil bones. One of those found bones was a tail vertebra, and that the hundred castings were all cast scale models based on that one found bone.
All this is meant to indicate how little absolute evidence actually exists regarding these very interesting creatures! Books, including textbooks, have always tried to make it seem that EVERYTHING is known about these creatures, where the reality is that very little is actually known! But progress seems to be rapidly progressing. In a valley in Montana, in the past few years, eight different T. Rex fossil sets have been found by an extensive team of researchers and college students. This is a good sign that future knowledge might soon improve!
Popular interest has inspired speculation about quite a number of apparently unusual characteristics of these extinct creatures and has since fueled controversy over these features and the causes for their existences. Little consideration seems to sometimes have been given related to the necessary physical consequences of these speculations and conclusions. Several of these matters will be discussed here.
In a related web page, I present a discussion about the necessary size of the mouth of a large dinosaur to be able to ingest enough food for enough energy audit for its size. Some truly huge sauropods are described as having rather tiny mouths, which seems to bring up interesting logical questions! Another related web page discusses the necessary muscle and tendon strengths necessary in the Mechanical Engineering in a very long neck, when the head might have weighed nearly a ton. To cantilever out that much weight thirty or forty feet or more in front of front legs creates a number of serious mechanical stresses, and they often seem to challenge current thinking in that the strongest known biological muscles and tendons seem unlikely to be able to withstand those levels of stress. Even the vertebrae and the disks between them need some extensive study and explanation! As a consequence of these aspects of Physics, I concluded that the largest of the sauropods could not have been land-dwelling animals and they must have been nearly constantly submerged in a swamp or shallow lake environment to provide the needed temperature aspects of the energy audit and also to benefit from some portion of flotation regarding strength and movement. Fully warm-blooded is nearly impossible, but being in a relatively warm swamp or pond could make the energy audit possible.
Most of the following comments are only intended to apply to the very largest of the land-based(?) dinosaurs, called Brontosaurus (Apatosaurus is the same thing), Diplodocus, Brachiosaurus, and Camarasaurus, and a few others, collectively referred to as Sauropods. Few of these comments apply to any of the smaller dinosaurs like the velociraptors, Tyrannosaurus Rex, Stegosaurus, etc. The comments regarding blood pressures and flows might apply to T. Rex, because of the 18-foot tall height it would have had when fully erect. (In that regard, the recent findings of many T. Rex fossils in Montana now suggest that the posture of a T. Rex was not as upright as had been commonly thought, and its torso was more horizontal. This would greatly agree with the blood flow considerations described below.)
Great Physical Mass of Brachiosaurs and Leg Structure
Most scientists believe that these sauropods had a living weight of up to 80 tons. (Apatosaurus [Brontosaurus] - 20 to 35 tons; Diplodocus - 11 to 15 tons; Brachiosaurus - around 80 tons) It is fairly simple to estimate the weight of any dinosaur. Nearly all organic materials have densities relatively similar to that of sea water. By measuring and estimating lengths, widths and heights, it is possible to determine the approximate volume of a dinosaur. Multiplying by the density of sea water gives an approximate weight.
As an example, (rib) fossils of a Brachiosaurus seem to imply that its trunk was around 12 feet in diameter and 20 feet long. Using the method suggested above, and thinking of its trunk as a cylinder, the volume V is given by (Pi)*D2/4 * L or about 3.14 * 144/4 * 20 or about 2,260 cubic feet. At 64 pounds per cubic foot (the density of nearly all biological material, essentially that of water), that gives about 145,000 pounds. Add some more for its head, neck, tail and feet, and you have around the 80 tons mentioned above. (That's pretty much how the experts first identified the estimated weights!)
That enormous weight, in itself, is amazing but not impossible for a living creature. The modern day Great Blue Whale actually weighs more than this. There have been stories of Great Blues, which have become beached at low tide, and their ribs have allegedly broken under their own weight. This is reasonable. While floating, the buoyancy of the water supports most of its weight, so a moderate-sized bone structure can maintain stability and bodily integrity. But on land, without that buoyancy, it could not survive. This sort of argument has been used regarding the largest sauropods to suggest that they must have lived in swamps or very shallow seas, in order to support their weight.
Other scientists believe that these large dinosaurs lived on dry land, that their legs and muscles were actually strong enough to support and move around this vast weight. Such scientists may be overlooking the fact that the mass we are talking about is equivalent to about 50 automobiles! The leg bones and muscles necessary to support and move this huge weight on dry land would necessarily be near the absolute limits of cell and bone and muscle fiber strength. The estimated mass of the brachiosaurus is on the scale of 20 elephants. Elephants' legs are rather stout to support the several tons of their weight. The proposed dinosaur mass would require MUCH more stout legs, possibly to an unrealistic extent.
For a leg to support four times the weight (on dry land) the leg bones and leg muscles must each be twice as thick (so their cross-sectional areas are four times as great). It doesn't actually matter if those bones are round or oval or square, or if they are solid or hollow. In the case of a brachiosaur that had a body weight of 16 times that of a 10,000-pound elephant, those bones and muscles would all have to be four times the thickness (sixteen times the cross-sectional area) that is present in the elephant. Where the elephant's leg may be about a foot in diameter, the brachiosaurus' legs would therefore have to be about four feet in diameter (if it was to be mobile on land).
Existing fossils do not support such extremely thick legs. The fossils of leg bones are certainly thick, but they are not four times as thick. It is far more likely that the swamp hypothesis has more validity, and that these extremely large dinosaurs would have been susceptible to broken leg bones if they would ever attempt to walk on land. (Medium and small sized dinosaurs did not have this limitation and DEFINITELY were land creatures.)
If such a huge animal had a leg bone break, its possibility of survival would drop to nearly zero. It would no longer have the mobility to go to food sources and it would be immobile and easy prey for many carnivorous predators to attack and kill.
Footprints
A related subject also applies. A human might weigh 200 pounds and have a foot that has an area of 1/4 square foot. While walking, there are times when one foot is in the air. At these times, the entire 200 pounds is supported on that 1/4 square foot, meaning that there is 800 pounds per square foot pressure between the foot and the surface it is on. On soft or muddy ground, a person's footprints may press a half-inch into the ground, leaving molds of the person's foot after the ground dried out.
The large brachiosaurs appear, due to fossils, to have had feet that had around three square feet area, and at least two of them were probably always in contact with the ground while such a creature would have been walking. The 160,000 pounds of its weight would therefore be supported by six square feet of area of contact between feet and ground. This gives a pressure of around 27,000 pounds per square foot, almost 40 times that of a human and many times that of any known modern creature. Such an animal walking on soft or muddy ground probably wouldn't sink in 40 times as deeply as a person, but certainly very deeply. It is very likely that such footprints would be pits of more than a foot deep, in even moderately soft ground, because of the enormous pressure created from the weight of the creature.
Some fossilized footprints have been found that have been identified as being made by large dinosaurs. These footprints tend to be just an inch or two deep. They still have enough detail to be identified as dinosaur footprints, so they are not shallow, eroded remnants of earlier, deeper ones. This implies that less pressure (weight per square foot) may have been present when the footprints were made (or the ground was extremely hard).
Some of these footprints are found to be spaced a substantial distance apart. Some investigators have compared that to the probable leg-length and similar relationships among modern creatures, and have concluded that the footprints are so far apart that they had to have been made by brachiosaurs or other sauropods RUNNING! For many reasons presented in this essay, such large, massive, cumbersome creatures almost certainly could only move very slowly, if on land. Running would be entirely out of the question. In addition, why would such an animal have ever developed the musculature to be able to run? These giant creatures are believed to be herbivores, so carnivorous pursuit of prey would never be necessary. There would be no value in being able to outrun predators, either. The exertion and energy waste from running would be truly foolish for a creature that already probably had to eat almost continuously to maintain even basic metabolism for 160,000 pounds of cells!
A logical explanation for shallower-than-expected footprints and longer-than-expected stride might exist. If such a creature lived in a shallow sea or swampy environment, where buoyancy supported much of its weight, it's footprints in the sea bottom would be shallower (due to less weight pressure on the foot) and farther apart (due to a floating/swimming effect). Of course, preservation of such footprints represents a problem. The sea would have to remain extremely calm, so the underwater footprints were not immediately obliterated by wave action. The sea floor would have to be some material like clay rather than sand, to better have well-defined impressions. And some sudden supply of additional sediment would have to appear to quickly fill in the footprints such that they could be preserved for us to later find.