This blog contains material I wrote and posted on between the years 2005 and 2011 only. It does not contain any new material. For newer writing, please check my main blog (Bill the Butcher).

Tuesday, 27 November 2012

Tyrant King Of The Buzzards

It came on great oiled, resilient, striding legs. It towered thirty feet above half of the trees, a great evil god, folding its delicate watchmaker's claws close to its oily reptilian chest. Each lower leg was a piston, a thousand pounds of white bone, sunk in thick ropes of muscle, sheathed over in a gleam of pebbled skin like the mail of a terrible warrior. Each thigh was a ton of meat, ivory, and steel mesh. And from the great breathing cage of the upper body those two delicate arms dangled out front, arms with hands which might pick up and examine men like toys, while the snake neck coiled. And the head itself, a ton of sculptured stone, lifted easily upon the sky. Its mouth gaped, exposing a fence of teeth like daggers. Its eyes rolled, ostrich eggs, empty of all expression save hunger. It closed its mouth in a death grin. It ran, its pelvic bones crushing aside trees and bushes, its taloned feet clawing damp earth, leaving prints six inches deep wherever it settled its weight.

All right, that was Ray Bradbury introducing Tyrannosaurus rex in his short story (later to be made into an unendurable film), A Sound Of Thunder [1]. Yes, Tyrannosaurus rex, which, unless you only learned to read yesterday, you know as the baddest goddamned dinosaur the world has ever seen.

Uh, actually...

Actually, of course, Tyrannosaurus rex wasn’t even the biggest predatory dinosaur, let alone the biggest dinosaur. The biggest predatory dinosaur we know of till date, Giganotosaurus, would’ve dwarfed any of the tyrannosaurids (there were several different types, of which the celebrated and much-hyped Tyrannosaurus was merely the largest). But this, really, isn’t about that.

What is it about, then? that Bradbury intro above. Now, imagine how it would have read like this:

It came on scaled, scuttling, clawed legs, head thrust forwards, a great evil god, its feathered arms held close to its fluffy feathered chest.

Feathers? Yeah, you’ve got that right...feathers.

According to an article [2] I read recently, Tyrannosaurus rex had feathers.

So it didn’t, apparently, look like this:

It, the article says, looked like this:

Now I found the entire idea so bizarre that I had to do a little research of my own.

And, to be sure, this is what I found [3]:

There’s as yet no proof that Tyrannosaurus rex had feathers. And the scientists concerned did not say they had feathers. What they said was that there was a possibility that some of the precursor species to Tyrannosaurus may have had protofeathers, which are more like filamentous hair than feathers. It’s the equivalent of your prehuman ancestors having a gorilla-like pelt, and speculating that this means that you must have one too. No impression of T rex skin recovered to date shows feathers, mosaic scales or anything.

Also, an animal the size of T rex would have had problems with the body overheating if it had had feathers or hair, because the larger the body the less comparative surface area, and the less heat loss. Compare to large African animals, all of whom have substantially reduced or altogether eliminated body hair, like hippos, elephants or rhinoceroses.

Speculation. Nothing, really, much more than that. But speculation sells. Facts don’t. Look at the Iraq invasion for example.

But maybe, as the article continues, only cold-climate Tyrannosaurs had feathers?

Now this sounds superficially plausible, but isn’t really much more than speculation built on speculation. There’s really no reason why Tyrannosauruses would be found in cold climates at all, whatever cold climates existed in a time when the world’s temperature was rather higher than it is now. There are reasons for this.

Now, let’s assume for the time being (I’ll discuss the assumption in a moment) that the tyrannosaurids were predators. Large animals, it’s obvious to all of us except the wilfully ignorant, need large amounts of food. Now, if tyrannosaurs were homoiothermous (so-called “warm-blooded”) animals, they would need much more food than poikilothermous (so-called “cold-blooded”) creatures; a snake might get by a month on a meal, but a shrew has to eat several times its own weight every day. And a large homoithermous predator, one the size of a tyrannosaur, would need truly daunting quantities of food.

Assuming the tyrannosaurids were predators, then, they would need to kill one or two very large prey animals at relatively short intervals, or else chase down and kill large numbers of small animals. Now, very large prey animals back in Tyrannosaurus’ day would have been thin on the ground in cold climates. While small dinosaurs were almost certainly homoithermous, the really big ones would’ve probably boiled inside their skins from their own body heat if they had to maintain a constant body temperature. Also, as with any other homoiotherm, you need more food to keep yourself going. Allied with a gigantic body size, the big dinos would have had to eat really terrifying amounts of vegetation to survive in cold climates...vegetation which, typically, does not grow in cold climates. You know, like the tundra ain't no rain forest?

OK, so maybe cold-climate tyrannosaurs chased down large numbers of small prey? Chances of that happening are low to zero. Try running down a mouse sometime; hunting a small prey animal is more difficult and requires much more energy than hunting a big one, and for much less ultimate reward. Tyrannosaurus would have died of expending more energy on the hunt than it got from the food it obtained.

Uh, well, perhaps the prey creatures were big, cold-blooded dinos? Or Tyrannosaur itself was?

To take the second question first, why would a cold-blooded T rex need feathers at all? Feathers are meant to keep the body warm, as is fur. Evolution doesn’t support the creation of functionless structures. Besides, there’s a reason why there are fewer and fewer snakes and other cold-blooded animals the more you proceed from the equator towards the poles; animals whose body temperatures vary according to the outside temperature don’t do so well when said outside temperatures drop sharply. Cold-blooded dinos in the Arctic? No!

Ergo, Tyrannosaurus rex couldn’t have flourished in temperatures cold enough to require feathers to maintain body heat, and in climates where it actually would have flourished, adults, at least, would probably be naked skinned. Chicks might have, of course, been feathered. They would, lacking body fat deposits and probably having to be more active in search of food than the adults, require help to maintain their body temperature.

Yes, some dinosaurs definitely had feathers. Some of the smaller dinosaurs most certainly were more like chickens than lizards, and some of them were the size of big chickens, too. But they were small. (I need to point out that it’s almost certain that birds are surviving dinos; it’s just evolution that makes them look different). And Tyrannosaurus wasn’t a small dinosaur.

But let’s for the moment assume Tyrannosaurus had feathers. Let’s grant the animal that. Would these feathers have caused problems in hunting? Could they have possibly been as bright as the illustration suggests? Wouldn’t that kind of plumage be too visible to prey species to be realistic?

I don’t really see why not...if we take a second look at the idea that Tyrannosaurus rex was a predator.

It may come as a surprise to some, but there’s actually a strong school of thought among palaeontologists arguing that the tyrannosaurids weren’t predators at all, but rather scavengers feeding on carrion [4]. Their small eyes, large olfactory lobes, weak forelimbs and heavy hind limbs all argue for a carrion eating lifestyle, as does the fact that no fossils have been found of other dinos which show the (highly characteristic) toothmarks of tyrannosaurids which have healed. That would prove predation, since no predator kills each time it attacks prey. At least a fair proportion of the prey always gets away and at least some of these wounded animals would live to heal the wounds. But we have not found a single such fossil...yet.

So, T rex could have bright feathers because, obviously, vultures don’t really need camouflage. And it might even have been a seasonal thing, with maybe only the bulls sporting bright plumage and that only during the breeding birds. Again.

Now, it’s perfectly possible that the tyrannosaurids weren’t purely scavengers. It's possible that like the African lion of today, which often steals hyaena kills, T rex used its superior strength and size to chase other smaller predatory dinosaurs off the carcasses of their prey. If so, brighter colours would not have been a disadvantage. They may even have been useful: a warning to the competitors to get away from the scene in time to spare T rex a fight. Darker colours, in contrast, would have been really useful only if T rex was an ambush predator attacking from hiding over short distances, and given its size that would probably have been difficult to achieve. If it hunted at all, it most likely chased its prey down.

I see the Tyrannosaurus rex following herds of herbivorous dinos, like hadrosaurs, on their migrations, feeding off the dead and dying, chasing other predators off their kills to steal them, and only hunting if it had to.

Having said all that, though, I rather like the idea of a Tyrannosaur looking like a giant bird. It would have been a pretty fearsome beast, too, as it chased you down.

The chicken in your run would have had an ancestor to be proud of.






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