Chapter 4: Characteristics of dinosaurs

The first is the limb structure. Dinosaurs and mammals have their legs projecting vertically from their bodies and not to the sides like reptiles.

The skeletal features of dinosaurs also have many characteristics in common with birds; some species like Compsognathus can hardly be differentiated from modern birds. In fact, when a specimen classified as Compsognathus was reexamined, it was found to have traces of feathers and therefore re-classified as Archaeopteryx. It has become clear that the gigantic carnivorous Tyrannosaurus also has a skeletal structure very similar to birds.

In China, fossils of the oldest bird was found, with the same head structure as Compsognathus and Archaeopteryx. Based on these facts, birds are now thought to have descended from dinosaurs instead of reptiles.

While the skeletal structure is similar to that of birds, the behavior of dinosaurs roaming the land bears a close resemblance to mammals living today. Evidence of child rearing, migration, and group hunting has been found. Unlike mammals though, dinosaurs had ribs that ran all the way down to cover their stomachs, and thus were unable to lie down on their sides and had to sleep squatting down like a bird sitting on eggs. And if so any reason a dinosaur fell over it would have had to expend a tremendous effort to right itself as it was unable to twist its body around.

Chapter 5: The truth of why dinosaurs died out (1)

First, need we assume that gravity has been at the same level throughout history? Changes in the gravitational force could have occurred. Let us assume that, for some reason, gravity increased at the end of the Cretaceous. Then we can solve many of the mysteries surrounding the end of the dinosaurs.

To begin with, the mystery of why the organism of this era were so large can be easily explained. Dinosaurs grew so large because there was much less gravity than today.

Let's just think about the effect of body size on animals. Assume there are 2 completely similar dinosaurs, except one is twice as large as the other. Since weight is proportional to the volume of the body, and we can calculate the weight by cubing 2, which would mean that the larger one weighs 8 times as much. What about the muscles that would be supporting that kind of weight?

Muscles is made of bundles of muscle fibers, and power is generated by each fiber. Therefore, the amount of power that can be generated is almost proportional to the number of muscle fibers, in other words, the size of the muscle's cross-section. At the same time, if the length of the muscle changes then the rate of contraction will go down, changing the work rate. But since the number of muscle fibers remains the same, the power generated by the muscle also remains the same. Therefore, muscular strength will only increase by 2 squared, or 4 times.

So for a doubling in body size, weight is increased by the cube, while muscular strength is increased only by the square. The same applies to bone strength, which is increased by the square in proportion to size.

For this reason, large animals move slower than smaller ones.

Then were dinosaurs that were far larger than African elephants able to support their own weight and also be active?

I'll be examining this point based on the ideas of Ted Holden. First, how weight can an animal support anyway? Since wild animals are difficult to study, let's look at humans. The current world weightlifting record is 260kg held by Chemerkin of Russia. As dinosaurs were quadrupedal, let's imagine a quadrupedal Chemerkin and double our figures.

A quadrupedal Chemerkin would weigh 330kg and the total weight he could lift would be 850kg, including his own body weight and the barbells. Since this figure is the result of continual maximum effort weight training, we can assume that it represents the maximum muscular strength.

Then let's apply this figure to Brachiosaurus, one of the heavier dinosaurs. Alexander had calculated its weight as 46.6 tons, which is on the lower end of the estimates for this species.

If we scale up the 330kg quadrupedal Chemerkin to 46.6 tons, that would mean an increase of 141 times. To calculate the body volume we get the cubic root of 141, which means volume has increased by 5.2 times. Muscular strength is calculated by squaring 5.2, which is about 27. Since the quadrupedal Chemerkin could carry 850kg, multiplying that by 27 gives us 23 tons.

Here we run into a big inconsistency. The scaled-up Chemerkin quadruped weighs 46.6 tons and is beyond the limits of the calculated muscular strength, meaning he would not have been able to carry his own weight. Furthermore, bone strength has increased only 27 times whereas his body weight has gone up by 141 times.

In weightlifting, the barbell is lifted with the arms. Since the total weight has gone up then perhaps he may be able to support a heavier load. However, even if he were able to hold twice his calculated muscular strength, which would come to 46 tons, that would still be less than his own weight. And by current standards Brachiosaurus is certainly no longer the heavyweight champion. If we consider larger dinosaurs like Seismosaurus and Argentinosaurus that weigh over 100 tons, they couldn't possibly have existed under the present gravitational levels.

Translated by Rie Ishida