Monsters

The world of Athas has vastly different creatures than the other DnD settings, and this is due to a number of factors. The environment is much more specialized and taxing, typical food sources have faded with the ever-receding greenery of the world, and racial cleansing are only a few of these factors, but they're fairly instrumental ones.

Herd beasts/animals like cows and goats and sheep don't exist anymore, but there are, of course, analogues, like the crodlu and the kanks. Crodlu are a kind of flightless riding bird, similar to large ostriches in function and temperament (read: they're ill-tempered) and kanks are giant, docile beetles that serve some farmers as cows would (they secrete a sweet nectar useful for brewing) and others as camels for long-distance travel both for riding and carrying. Look here for stat ideas.

Because the world is way harsher and moisture is far more precious, most of the extant megafauna are things much more akin to giant beetles, birds, or reptiles.

As far as the cleansings are concerned, there are no gnomes, trolls, orcs, goblins, pixies, giants (other than Beastheads or the plains giants), kobolds, ogres, wemics, or tari. These creatures/races were exterminated by Rajaat the Warbringer's champions, the now sorcerer-kings.