There aren't a lot of high-level animals, no. Technically speaking, you can call any "type" of animal you like. Since a dire wolverine is a different type of animal than an ordinary wolverine, I would have no problem with allowing you to call such an animal, but you'd not be able to add a template to an ordinary wolverine in the process of calling..... and, of course, if there are no dire wolverines in the area, the spell fails.
In most deserts, my go-to Call'ed Animal would be a roc, a creature of Arabian folklore and very at home in the desert. There are also many snakes and similar reptiles, including the megalania (a giant lizard). You might also get dinosaurs of various sorts.
But to some extent you need your DM's cooperation. A "realistic" DM will note that large animals are rare, and that predators are rare, so large predators like an allosaurus should be almost nonexistent. But this would apply to other encounters, as well. If you're walking through the Desert of Snakes and you've fought three Giant Pit Vipers in the past hour, obviously he's not running off of realistic ecosystems.....
