Allosaurus, Merging Both Ideas

So, both Bakker and Sanchez take the data from the Cambridge study as a basis or their theories. Neither of them disagrees with the original data, just the interpretation. Which I find is an intrinsically personal situation. Basically you take a mathematically proven idea, in this case the stress analysis and see how it fits into your own theories on how the animal fed. The problem is that is a very broad conclusion to make.

We’ll look at it in context with other factors and lets see where that takes us.

We know that A. Fragilis could drive it’s head downward with great force thanks to the clever set up of it’s musculature. We know that the tooth row could withstand quite a bit of force which is congruent with a downward impact. That is not in dispute.

We also know that the animal is known to predate medium sized animals and occasionally larger prey. There is ample evidence in the record of Allosaurus bite marks on Stegosaurs and occasionally Camarasaurs. But which one of these two very different animals was the prey of choice for an Allosaurus?

The evidence I feel is in the relative size of the animal in question.

If we look at the mechanics of the swing of an Allosaurus head when employed in the manner that Bakker and Rayfield suggest, then the answer becomes obvious. If the animal is the same height or larger than an Allosaurus, it becomes increasingly more difficult for the Allosaurus skull to be brought down from above with any kind of force. It would be akin to trying to hit an elephant over the head with a baseball bat. - Unless the elephant is lying down, then you need to climb up or drop from a tree. Neither scenario is likely for a 30ft plus lizard.

Whether it brought it down like an axe, or carefully aimed for some of the more fleshy areas of an animal,(ie Sanchez) the fact still remains that whatever the method employed the force was directed upwards against the skull, which means that initially the Allosaurus head was above the bite point. That is an important factor when selecting the prey.

Considering that the head of an Allosaurus only reached shoulder level on Camarasaurus, such a method of predation would have been ineffective at best.

If we consider that to be correct, then the question becomes what kind or size of animal would this method of predation be most effective with.

First we can consider the other adaptations that Allosaurus had.  Namely it’s claws. They were big. They were attached to powerful forearms and were obviously used in some part for predation unlike the arms of the later Tyrannosaurs. Recent studies have shown that these arms could not pronate (hold the palms down). Allosaurus in short, could only hug. It couldn’t hang from the side of a large Sauropod and use it’s foot claws as is sometimes depicted. Likewise it could not use the hands to press down on very small prey prior to delivering the killing stroke.

Such rules out very large and very small prey.

Which leaves an animal slightly shorter than a standing Allosaurus. An animal slower than an Allosaurus and not as nimble. The primary candidate for which I feel is the Stegosaurus.

If we look at the picture below showing the reletive size of the two animals, and keep in mind the evidence suggested above, you can see how well the theory fits.

We’ll need to directly compare the two animals in the next post to examine how far the idea takes us.

So... what do you think? Please leave me a comment.