So here goes: Athas is an inhospitable desert, there's very few fauna, what is left are the most tenacious of plants. The animals/monsters as well, have need special adaptations just to survive. And yet, looking at the pack and transport animals, mountable monsters and desert creatures.... they 're all huge.
Now: Shouldn't those have died out first, considering the amounts of water they must consume?
Ok, so they're predators, they eat other animals... and what do they eat?
Has anyone considered an Athasian answer to this? Sorry to point this out. I know the obvious answer is of course: "It's not real! It's just a game"
But you know one of the players is bound to ask and nothing will kill suspension of disbelief quicker than than having no answer to something as fundamental.
Are sizeable pack animals Rare that only the merchant houses have a few off, relaying them between the few oasis. Still what do they eat?
What about roaming monsters?
Is the desert perhaps less deserted than I imagine, and not unlike real life deserts they are teeming with small creatures (insects,mice,lizards)
So it's a normal desert then?
Sorry I'm sure this has a very plausible answer, just can't think of one.
i have found it here:
http://www.geocities.com/Area51/Vault/2549/ecocolor.pdf
"The use of the Tower resulted in the loss of all the oceans, the sudden appearance of at least one major continental landmass, and the opening up of millions of new ecological niches. Aquatic creatures would have been incredibly plentiful during the blue age, comprising the greatest percentage of life forms. Once the tower was used and the oceans started drying up, aquatic creatures would have almost entirely died out in a very short span of time, with only a very, very few surviving and adapting to the new dry environment."
followed by:
"In fact, if the mutations were drastic enough, perhaps aquatic creatures did turn into some of today’s creatures. For example, silt horrors could be mutated jellyfish, and DMs may wish to add some aquatic traits to some of today’s creatures"
Fish or aquatic like features in deep desert creatures is bound to hint the players in investigating the world a bit deeper and foreshadows later blue age fluff.
I also like how this article actualy explains how the ecology and every creature on the face of athas having at least a minimum of psionics are clearly related. So the setting married with the abundance of psionics realy fits.
This is such a good article! TEOS ABADIA & GERALD ARTHUR LEWIS: these guys realy did their homework.
I'm re-reading my own netbook today! 
I'm still a big fan of desert ecology, both on Athas and in the real world. Guess I didn't get enough play time in the sandbox as a kid... or maybe too much...
Yeah. Quality research in your project, Teos!
Huge animals, like Mekillots certainly should require many tons of food that would be difficult to sustain in a desert, but speaking as a biologist, larger animals can afford to be less efficient in terms of caloric intake and homeostasis. They won't have to eat as often to maintain energy reserves and body temperature as some tiny little rodent. Reptiles, in particular often have metabolisms that let them enter torpor/hibernation modes when conditions are harsh.
And of course, there are lots of species on Earth that are selectively bred for agricultural yield or economic function and really would not survive at all in their present form without humans. (Corn, and teacup poodles, for example)
Thanks! It helps make up for how much I let everyone down on the weapons book, I hope. *cringe* (shall we start that project up again once the 4E books come out...?)
On the super-large creatures... they really need some undiscovered food source (think whales skimming plankton but turn it into some sort of sand plankton...), or a long dormancy period, or migrations of critters from outside the desert area once per season, or magic, or... I mean, some of those monsters are insane huge... maybe they appear magically from elemental force, largely live off of it, kill anything they find, then dissipate.
For the normal-sized stuff, it can work. The Athasian world did a nice job of capturing the largely true range of what a desert is. A desert can fit the technical definition and still support a lot of life (including creatures like elephants, which migrate across deserts without much water).
I've used (with permission) materials from the old 
Arms of Athas net project - is it the unfinished project your writing about?
Regardless, it has proven useful, and I'm sure it will be a source of inspiration for this edition as it was for the last.
I suspect that was the attempt to make up for my disappearance! Did that project get published into pdf or similar form?
Weapons from the net book have been integrated in the Athasian Emporium, which is the athas.org and DS equivalent of WotC's 3rd ed Arms & Equipment Guide. It can be found on athas.org site.