DINOSAURS and the Gravity Problem

Scientists delight in devising explanations for the great dinosaur extinctions. But there are several questions which they have failed to even ask, much less tried to answer. Why, for instance, in all of the time claimed to have passed since the dinosaur extinctions, has nothing ever re-evolved to the sizes of the large dinosaurs? If such sizes worked for creatures which ruled the Earth for tens of millions of years, then why would not some species of elephant or rhinoceros have evolved to such a size again? What kinds of problems, if any, would sauropod sizes entail in our world as it is presently constituted? Could it be that some aspect of our environment might have to be massively different for such creatures to exist at all? A careful study of the sizes of these antediluvian creatures, and what it would take to deal with such sizes in our world, has led me to believe that the super animals of Earth's past could not live in our present world at all.

A look at sauropod dinosaurs as we know them today requires that we relegate the brontosaur, once thought to be one of the largest sauropods, to welterweight or at most middleweight status. Fossils found in the 1970's now dwarf this creature. Both the brachiosaur and the supersaur were larger than the brontosaur, and the ultrasaur appears to have dwarfed them all.1 The ultrasaur is now estimated to have weighed 180 tons.2

A comparison of dinosaur lifting requirements to human lifting capabilities is enlightening, though there might be objections to do- ing so. One objection that might be raised is that animal muscle tissue was somehow "better" than that of humans. This, however, is known not to be the case. According to Knut Schmidt-Nielson, author of Scaling: Why is Animal Size So Important?, the maximum stress or force that can be exerted by any muscle is independent of body-size and is the same for mouse or elephant muscle.3

Another objection might be that sauropods were aquatic crea- tures. But nobody believes that anymore; they had no adaptation for aquatic life, their teeth show wear and tear which does not come from eating soft aquatic vegetation, and trackways show them walking on land with no difficulty.

A final objection might be that dinosaurs were somehow more "efficient" than top human athletes. This, however, goes against all observed data. As creatures get bulkier, they become less efficient; the layers of thick muscle in limbs begin to get in each other's way and bind to some extent. For this reason, scaled lifts for the super- heavyweight athletes are somewhat lower than for, say, the 200-pound athletes. By "scaled lift" I mean a lift record divided by the two-thirds power of the athlete's body weight.

As creatures get larger, weight, which is proportional to volume, goes up in proportion to the cube of the increase in dimension. Strength, on the other hand, is known to be roughly proportional to the cross-section of muscle for any particular limb and goes up in proportion to the square of the increase in dimension. This is the familiar "square-cube" problem.4

Consider the case of Bill Kazmaier, the king of the power lifters in the 1970s and 1980s. Power lifters are, in my estimation, the strongest of all athletes; they concentrate on the three most difficult total-body lifts, i.e. bench press, squat, and dead-lift. They work out many hours a day and, it is fairly common knowledge, use food to flavor their anabolic steroids. No animal the same weight as one of these men could be presumed to be as strong. Kazmaier was able to do squats and dead lifts with weights between 1,000 and 1,100 pounds on a bar, assuming he was fully warmed up.

Any animal has to be able to lift its own weight off the ground, i.e. stand up, with no more difficulty than Kazmaier experiences doing a 1,000-pound squat. Consider, however, what would happen to Mr. Kazmaier, were he to be scaled up to 70,000 pounds, the weight commonly given for the brontosaur. Kazmaier's maximum effort at standing, fully warmed up, assuming the 1,000 pound squat, was 1,340 pounds (1,000 pounds for the bar and 340 pounds for himself). The scaled maximum lift would be 47,558 pounds (the solution to: 1,340/340.667= x/70,000.667). Clearly, he would not be able to lift his weight off the ground!

A sauropod dinosaur had four legs you might say; so what happens if Mr. Kazmaier uses arms and legs at 70,000 pounds? The truth is that the squat uses almost every muscle in the athlete's body very nearly to the limits, but in this case, it does not even matter. A near maximum bench press effort for Mr. Kazmaier would fall around 600 pounds. This merely changes the 1,340 pounds to 1,940 pounds in the equation above, and the answer comes out as 68,853 pounds. Even using all muscles, some more than once, the strongest man who we know anything about would not be able to lift his own weight off the ground at 70,000 pounds.

To believe then, that a brontosaur could stand at 70,000 pounds, one has to believe that a creature whose weight was mostly gut and the vast digestive mechanism involved in processing huge amounts of low-value foodstuffs was, somehow, stronger than an almost entirely muscular creature its size, far better trained and conditioned than any grazing animal. That is not only ludicrous in the case of the brontosaur, but the calculations only become more absurd when you try to scale up to the supersaur and ultrasaur at their sizes.

How heavy can an animal get to be in our world, then? How heavy would Mr. Kazmaier be at the point at which the square-cube problem made it as difficult for him to stand up as it is for him to do 1,000-pound squats at his present weight of 340 pounds? The answer is 20,803 pounds (the solution to: 1,340/340.667= ). In reality, elephants do not appear to get quite to that point. Christopher McGowan, curator of vertebrate paleontology at the Royal Ontario Museum, claims that a Toronto Zoo specimen was the largest in North America at 14,300 pounds,5 and Smithsonian personnel once informed me that the gigantic bush elephant specimen which appears at their Museum of Natural History weighed around 8 tons.

A study of the sauropod dinosaurs' long neck further under- scores the problem these creatures would have living under current gravitational conditions. Scientists who study sauropod dinosaurs now claim that they held their heads low, because they could not have got- ten blood to their brains had they held them high.6 McGowan mentions the fact that a giraffe's blood pressure -- which at 200-to-300 mm Hg (millimeters of mercury) is far higher than that of any other animal -- would probably rupture the vascular system of any other animal. The giraffe's blood pressure is maintained by thick arterial walls and by a very tight skin that apparently acts like a jet pilot's pressure suit. A giraffe's head might reach to 20 feet.

How a sauropod might have gotten blood to its brain at 50 or 60 feet is the real question."Gravity is a pervasive force in the environment and has dramatically shaped the evolution of plants and animals," notes Harvey Lillywhite, a zoologist at the University of Florida at Gainesville. As some land animals evolved large body sizes, "cardiovascular specializations were needed to help them withstand the weight of blood in long vertical vessels. Perhaps nowhere in the history of life were these challenges greater than among the gigantic, long-necked sauropods" For a Barosaurus to hold its head high, Lilly- white has calculated that its heart "must have generated pressures at least six times greater than those of humans and three to four times greater than those of giraffes." 7

Faced with the same dilemma, University of Pennsylvania geologist Peter Dodson remarked that while the Brachiosaurus was built like a giraffe and may have fed like one, most sauropods were built quite differently."At the base of the neck," Dodson writes,"a sauropod's vertebral spines, unlike those of a giraffe, were weak and low and did not provide leverage for the muscles required to elevate the head in a high position. Furthermore, the blood pressure required to pump blood up to the brain, thirty or more feet in the air, would have placed extraordinary demands on the heart and would seemingly have placed the animal at severe risk of a stroke, an aneurysm, or some other circulatory disaster."8

The only way to keep the required blood pressure "reasonable," Dodson goes on to add, is "if sauropods fed with the neck extended just a little above heart level, say from ground level up to fifteen feet..." One problem with this solution is that the good leaves were, in all likelihood, above the 20-foot mark; an ultrasaur that could not raise its head above 20 feet would probably starve. Dodson, it should also be noted, entirely neglects the dilemma of the brachiosaur. And there is another problem, which is worse. Try holding your arm out horizon- tally for even a few minutes, and then imagine your arm being 40 feet long.

Given a scale model and a weight figure for the entire dinosaur, it is possible to use volume-based techniques to estimate weight for a sauropod's neck. An ultrasaur is generally thought to be a near cousin -- if not simply a very large specimen -- of the brachiosaur. The technique, then, is to measure the volume of water which the sauropod's neck (severed at the shoulders and filled with bondo or auto- body putty) displaces, versus the volume which the entire brachiosaur displaces, and simply extrapolate to the 360,000-pound figure for the ultrasaur. I did this using a Larami Corporation model of a brachiosaur, which is to scale. To make a long story short, the neck weighs 28,656 pounds, and the center of gravity of that neck is 15 feet from the shoulders, the neck itself being 38 feet long. This equates to 429,850 foot-pounds of torque.

If we assume the sauropod could lift its head at least as easily as a human with an 18-inch neck can move his head against a neck- exercise machine set to 130 pounds, then the sauropod would require the muscular strength of a neck 17.4 feet in diameter. With a more reasonable assumption of effort, equivalent to the human using a 50-pound setting, the sauropod would require a neck of over 20 feet in diameter. But the sauropod's neck, at its widest, apparently measured about ten feet by seven feet where it joined the shoulders, then nar- rowed rapidly to about six or seven feet in diameter over the remain- der of its length. McGowan and others claim that the head and neck were supported by a dorsal ligament and not muscles, but we know of no living creature using ligaments to support a body structure which its available musculature cannot sustain. In all likelihood, sauropods, in our gravity at least, could neither hold their heads up nor out.

The large flying creatures of the past would also have had difficulties in our present-day gravity. In the antediluvian world, 350-pound flying creatures soared in skies which no longer permit fly- ing creatures above 30 pounds or so. Modern birds of prey, like the Argentinian teratorn, weighing 170 to 200 pounds, with 30-foot wing- spans, also flew. Within recorded history, Central Asians have been trying to breed hunting eagles for size and strength, and have not got- ten them beyond 25 pounds or thereabouts. Even at that weight they are able to take off only with the greatest difficulty. Something was vastly different in the pre-flood world.

Nothing much larger than 30 pounds or so flies anymore, and those creatures, albatrosses and a few of the largest condors and eagles, are marginal. Albatrosses, notably, are called "goonie birds" by sailors because of the extreme difficulty they experience taking off and landing, their landings being badly controlled crashes, and this despite long wings made for maximum lift.

In remote times, the felt effect of the force of gravity on Earth must have been much less for such giant creatures to be able to fly. No flying creature has since re-evolved into anything of such size, and the one or two birds that have retained this size have forfeited flight, their wings becoming vestigial.

Adrian Desmond, in his book The Hot-Blooded Dinosaurs, has a good deal to say about some of the problems the Pteranodon faced at just 40-to-50 pounds. Scientists once thought this pterosaur was the largest creature that ever flew. The bird's great size and negligible weight must have made for a rather fragile creature."It is easy to imagine that the paper-thin tubular bones supporting the gigantic wings would have made landing dangerous," writes Desmond. "How could the creature have alighted without shattering all of its bones? How could it have taken off in the first place? It was obviously unable to flap 12-foot wings strung between straw-thin tubes. Many larger birds have to achieve a certain speed by running and flapping before they can take off and others have to produce a wing beat speed approaching hovering in order to rise. To achieve hovering with a 23-foot wingspread, Pteranodon would have required 220 pounds of flight muscles as efficient as those in humming birds. But it had re- duced its musculature to about 8 pounds, so it is inconceivable that Pteranodon could have taken off actively."9

Since the Pteranodon could not flap its wings, the only flying it could ever do, Desmond concludes, was as a glider. It was, he says, "the most advanced glider the animal kingdom has produced."10 Desmond notes a fairly reasonably modus operandi for the Pteranodon. Not only did the bird have a throat pouch like a pelican but its remains were found with fish fossils, which seems to suggest a pelican-like existence, soaring over the waves and snapping up fish without landing. If so, then the Pteranodon should have been practically immune from the great extinctions of past ages. Large animals would have the great- est difficulty getting to high ground and other safe havens at times of floods and other global catastrophes. But high places safe from flood- ing were always there, oceans were always there, and fish were al- ways there. The Pteranodon's way of life should have been impervious to all mishap.

There is one other problem. The Pteranodon was not the largest bird. The giant Terotorn finds of Argentina were not known when Desmond's book was written. News of this bird's existence first appeared in the 1980s. The Terotorn was a 160-to-200 pound eagle with a 27-foot wingspan, a modern bird whose existence involved, among other things, flapping wings and aerial maneuvers. But how so? How could it even have flown?

How large can an animal be and still fly?"With each increase in size, and therefore also weight," writes Desmond,"a flying animal needs a concomitant increase in power (to beat the wings in a flapper and to hold and maneuver them in a glider), but power is supplied by muscles which themselves add still more weight to the structure. The larger a flyer becomes the disproportionately weightier it grows by the addition of its own power supply. There comes a point when the weight is just too great to permit the machine to remain airborne. Calculations bearing on size and power suggested that the maximum weight that a flying vertebrate can attain is about 50 pounds..."

It is for this reason that scientists believed Pteranodon and its slightly larger but lesser known Jordanian ally Titanopteryx were the largest flying animals of all time. The experience from our present world coincides well with this and, in fact, don't go quite that high. The biggest flying creatures which we actually see are albatrosses, geese, and the like, at 30 to 35 pounds.

The Pteranodon's reign as the largest flying creature of all time actually fell in the early 1970s when Douglas Lawson of the University of California found partial skeletons of three ultra-large ptero- saurs in Big Bend National Park in Texas. This discovery forced scientists to rethink their ideas on the maximum size permissible in flying vertebrates. The immense size of the Big Bend pterosaurs may be gauged by noting that the humerus or upper arm bones of these creatures is fully twice the length of Pteranodon's. Lawson estimated the wingspan for this living glider at over fifty feet.

The Big Bend pterosaurs were not fishers. Their remains were found in rocks that were formed some 250 miles inland and nowhere near any lake deposits. This led Lawson to suggest that these birds were carrion feeders, gorging themselves on rotting mounds of dismembered dinosaur flesh. But this hypothesis raised numerous questions in author Desmond's mind.

"How they could have taken to the air after gorging them- selves is something of a puzzle," he wonders."Wings of such an extraordinary size could not have been flapped when the animal was grounded. Since the pterosaurs were unable to run in order to launch themselves they must have taken off vertically. Pigeons are only able to take-off vertically by reclining their bodies and clapping the wings in front of them; as flappers, the Texas pterosaurs would have needed very tall stilt-like legs to raise the body enough to allow the 24-foot wings to clear the ground. The main objection, however, still rests in the lack of adequate musculature for such an operation." 12 The only solution seems to be that they lifted passively off the ground by the wind. But this situation, notes Desmond, would leave these ungainly Brobdignagian pterosaurs vulnerable to attack when grounded.

While Desmond mentions a number of ancillary problems here, any of which would throw doubt on the pterosaur's ability to ex- ist as mentioned, he neglects the biggest question of all: the calculations that say 50 pounds are the maximum weight have not been shown to be in error; we have simply discovered larger creatures. Much larger. This is what is called a dilemma.

Those who had estimated a large wingspan for the Big Bend bird were immediately attacked by aeronautical engineers."Such dimensions broke all the rules of flight engineering," wrote Colorado paleontologist Robert T. Bakker, in The Dinosaur Heresies,"a creature that large would have broken its arm bones if it tried to fly..." 13 Subsequently, the proponents of a large wingspan were forced to back off somewhat, since the complete wing bones had not been discovered. But Bakker believes these pterosaurs really did have wingspans of over 60 feet and that they simply flew despite our not comprehending how. The problem is ours, he says, and he proposes no solution.

So much for the idea of anything re-evolving into the sizes of the flying creatures of the antedeluvian world. What about the possibility of man breeding something like a Teratorn? Could man actively breed even a 50-pound eagle?

Berkuts are the biggest of eagles. And Atlanta, an eagle that Sam Barnes, one of England's top falconers in the 1970s, brought back to Wales from Kirghiz, Russia, is, at 26 pounds in flying trim, as large as they ever get.14 These eagles have been bred specifically for size and ferocity for many centuries. They are the most prized of all possessions amongst nomads, and are the imperial hunting bird of the Turko-Mongol peoples. The only reason Barnes was allowed to bring her back is that Atlanta had a disease for which no cure was available in Kirghiz and was near to death. A Berkut of Atlanta's size, Barnes was told, would normally be worth more than a dozen of the most beautiful women in Kirghiz.

The killing powers of a big eagle are out of proportion to its size. Berkuts are normally flown at wolves, deer, and other large prey. Barnes witnessed Atlanta killing a deer in Kirghiz, and was told that she had killed a black wolf a season earlier. Mongols and other no- mads raise sheep and goats, and obviously have no love for wolves. A wolf might be little more than a day at the office for Atlanta with her 11-inch talons, however, a wolf is a big deal for an average-sized Berkut at 15-to-20 pounds. Obviously, there would be an advantage to having the birds be bigger, i.e. to having the average Berkut weigh 25 pounds, and for a large one to weigh 40-to-50 pounds. It has never been done, however, despite all the efforts and funds poured into the enterprise since the days of Genghis Khan. The breeding of Berkuts has continued apace from that day to this, but the Berkuts have still not gotten any bigger than 25 pounds or so.15

It is worth recalling here the difficulty which increasingly larger birds experience in getting airborne from flat ground. Atlanta was powerful enough in flight, but she was not easily able to take off from flat ground. This could spell disaster in the wild. A bird of prey will often land with prey, and if take-off from flat ground to avoid trouble is not possible, the bird's life becomes imperiled. A bird big- ger than Atlanta with her 10-foot wingspan, like a Teratorn with a 27-foot wingspan and weighing 170 pounds, would simply not Survive.

There are other categories of evidence, derived from a careful analysis of antediluvian predators, to show that gravitational condi- tions in the distant past were not the same as they are today. It is well known, for example, that elephant-sized animals cannot sustain falls, and that elephants spend their entire lives avoiding them. For an elephant, the slightest tumble can break bones and/or destroy enough tissue to prove fatal. Predators, however, live by tackling and tumbling with prey. One might think that this consideration would preclude the existence of any predator too large to sustain falls. Weight estimates for the tyrannosaurs, however, include specimens heavier than any elephant. That appears to be a contradiction.

Moreover, elephants are simply too heavy to run in our world. As is well known, they manage a kind of a fast walk. They cannot jump, and anything resembling a gully stops them cold. Mammoths were as big and bigger than the largest elephants, however, and Pleis- tocene art clearly shows them galloping.

Finally, there is the Utahraptor. Recently found in Utah, this creature is a 20-foot, 1,500-pound version of a Velociraptor.16 The creature apparently ran on the balls of its two hind feet, on two toes in fact, the third toe carrying a 12-inch claw for disemboweling prey. This suggests a very active lifestyle. Very few predators appear to be built for attacking prey notably larger than themselves; the Utahrap- tor appears to be such a case.

In our world, of course, 1,500-pound toe dancers do not exist. The only example we have of a 1,500-pound land predator is the Ko- diak bear, the lumbering gait and mannerisms of which are familiar to us all. And so, over and over again, this same kind of dilemma-things which cannot happen in our world having been the norm in the antediluvian world.

The laws of physics do not change, nor does the gravitational constant, as far as we know. But something was obviously massively different in the world in which these creatures existed, and that differ- ence probably involved a change in perceived gravity. This solution derives from the continuing research of neo-catastrophists, that is, fol- lowers of the late Immanuel Velikovsky, and is known as the "Saturn Myth" theory.17

The basic requirement for an attenuated perception of gravity involves the Earth being in a very close orbit around a smaller and much cooler stellar body (or binary body) than our present Sun. One pole would always be pointed directly at this nearby small star or binary system. The intense gravitational attraction would pull the Earth into an egg shape rather than its present spherical shape, so that the planet's center of gravity would be off center towards the small star. This would generate the torque necessary to counteract the natu- ral gyroscopic force and keep the Earth's pole pointed in the same direction as it revolved around the star.

The consequences of this intense gravitational pull would be dramatic. It would allow, first of all, for gigantic animals like the dinosaurs (just as any change in gravity to the present situation would likely cause their demise). It would also tend to draw all of the Earth's land mass into a single supercontinent (Pangea). Why else, after all, should the Earth's continental masses have amassed in one place? And finally, with the Earth's pole pointed straight at this star or binary sys- tem, there would be no seasons. All literature of the distant past points out that the seasons did not appear until after the flood.

The state of the present solar system indicates that this pre- vious system was eventually captured by a larger star, our present Sun. But the pieces of this old system have not vanished. The influential small star or binary system of the past remains, though its reign of power has ended. The star or stars are Jupiter and Saturn, the next largest objects to the Sun in our present system.

It is instructive that the ancients worshiped Jupiter and Saturn as the two chieftain gods in all of the antique religious systems. If the present solar system was present in the distant past, one would expect primitive peoples to have worshiped the most visible of the astral bodies: the Sun, the Moon, and Venus. There is no conceivable reason they would worship as gods two planets which most people cannot even find in the night sky -- unless, of course, these bodies occupied a far more prominent place in the heavens than they do today.

1.David Lambert and the Diagram Group Staff, Field Guide to Dinosaurs: The First Complete Guide to Every Dinosaur Now Known, New York, 1983, p. 118.

2.Christopher McGowan, Dinosaurs, Spitfires & Sea Dragons, Cam- bridge, 1991, p. 118.

3.Knut Schmidt-Nielson, Scaling, Why is Animal Size So Important?, Cambridge, 1984, page 163."It appears that the maximum force or stress that can be exerted by any muscle is inherent in the structure of the muscle filaments. The maximum force is roughly a 3 to 4 kgf/cm2 cross-section of muscle (300-400 kN/m2). This force is body-size independent and is the same for mouse and elephant muscle. The reason for this uniformity is that the dimensions of the thick and thin muscle filaments, and also the number of cross-bridges between them are the same. In fact the structure of mouse muscle and elephant muscle is so similar that a microscopist would have difficulty identifying them except for a larger number of mitochondria in the smaller animal. This uniformity in maximum force holds not only for

higher vertebrates, but for many other organisms, including at least some, but not all invertebrates."

4.The normal inverse operator for this is to simply divide by 2/3 power of body weight, and this is indeed the normal scaling factor for all weight lift- ing events, i.e. it lets us tell if a 200-pound athlete has actually done a "bet- ter" lift than the champion of the 180-pound group. For athletes roughly between 160 and 220 pounds, i.e., whose bodies are fairly similar, these scaled lift numbers line up very nicely. It is then fairly easily seen that a lift for a scaled up version of one particular athlete can be computed via this

formula, since the similarity will be perfect, scaling being the only difference.

7.Harvey B. Lillywhite,"Sauropods and Gravity", Natural History, De- cember, 1991, p. 33."...in a Barosaurus with its head held high, the heart had to work against a gravitational pressure of about 590 mm of mercury

(Hg). In order for the heart to eject blood into the arteries of the neck, its pressure must exceed that of the blood pushing against the opposite side of the outflow valve. Moreover, some additional pressure would have been needed to overcome the resistance of smaller vessels within the head for blood flow to meet the requirements of brain and facial tissues."

8.Peter Dodson,"Lifestyles of the Huge and Famous," Natural History, December, 1991, p.32.

9.Adrian J. Desmond, The Hot-Blooded Dinosaurs: A Revolution in Pa- leontology, New York, 1976, p. 178.

It is instructive that the ancients worshiped Jupiter and Saturn as the two chieftain gods in all of the antique religious systems. If the present solar system was present in the distant past, one would expect primitive peoples to have worshiped the most visible of the astral bodies: the Sun, the Moon, and Venus. There is no conceivable reason they would worship as gods two planets which most people cannot even find in the night sky — unless, of course, these bodies occupied a far more prominent place in the heavens than they do today.

Or perhaps the alleged collision that caused the moon and added mass to the earth had not happened yet?

Thought that was the argument for the now-”debunked” young earth theory, though that would not agree with “settled science”.

(Now that we recently re-wrote all the History, Science and Astronomy books to include the Fraud and his anthropomorphic climate change dogma).

People need to be careful with their arguments. Let the evolutionist be the sloppy ones often teaching badly outdated notions of evolution in public schools if only because its hard to keep up ... and also keeping up may not be important if, as is likely the deep motivation, evolution is used as a way to foster secularism and atheism through the schools.

Most dinosaurs weren’t huge.

But for the biggest there may be a way to explain why they grew so large: possibly poor quality food.

The normal views on ancient plant life from looking at the teeth was that it was frequently tough fare.

Now, there are tough to digest plants being eaten by herbivores all the time today, such as grass, and the way active creatures (not talking koalas who sleep off their meals a lot) to digest. Among the most efficient if fermentation which is likely method used by the biggest dinosaur herbivores.

Cattle for example use fermentation with their multisegmented stomach (4 chambers IIRC) that serves to efficiently digest but they have a number of additional tactics, like chewing their cud, that dinosaurs probably didn’t have.

But if relying strictly on fermentation there would be a real benefit from having a very big stomach or just lots and lots of intestines because fermentation is one of those processes that benefits from economies of scale, with a big stomach taking less energy for a given amount of food to extract the same energy.

So a big stomach translates into a big animal. The classical long necked giant would have also had to have moved less since they could swing their heads side to side sucking up whatever they came across.

With generally better quality plant food and sometimes better strategies to digest what is marginal, there simply is no advantage to growing so very big, never mind huge, and with big herbivores being smaller / less common there’s reduced opportunity for there to be big meat eaters.

Another perhaps more believable theory is that during the Mesozoic, Earth had a slightly higher rotation rate which would lessen gravity slightly. More importantly the Earth's atmosphere was much thicker than today, giving more buoyancy to large animals. Slightly lower gravity, air 2/3rds that of water and very large animals become possible.

ρF = ρS (1 - 1/S.F.)
where ρF is the density of the fluid, ρs is the density of the substance submerged in the fluid such as the dinosaur, and S.F is the scaling factor. Inserting into this equation a scaling factor of 3.2 and an overall vertebrate density of 970 kg/m3, the Earth's atmospheric density during the late Jurassic period can be calculated to be 670 kg/m3. This says that to produce the necessary buoyancy so that the dinosaurs could grow to their exceptional size, the density of the Earth’s air near the Earth’s surface would need to be 2/3’s of the density of water. (ref: https://dinosaurtheory.com/solution.html)

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