In my fantasy world there is a large valley. At the northern end lies the 'endless desert' called the "Sea of Glass" due to its shimmering sands. Within these deserts live great wyrms that swim through the sand as if it was an ocean.
The wyrms/worms would roughly have these dimensions: 4 meters high and wide and stretching to lengths between 10 to 30 meters. The 'mouth' of the beast is cylindrical however their mouth is protected by a beak that is enclosed during burrowing (making a cone shape).
The worms most likely breath oxygen and would need to resurface (think about the same time as a humpback whale). Their main hunting strategy is to stalk their prey using echolocation to hear footsteps above the sand then the worm would launch its self forward and open their beak aiming to suddenly swallow and enclose their prey.
These worms are pretty big critters. I'm wondering if a purely carnivorous diet would be able to sustain a worm of this size as well as possible eating habits as a bonus (ex: would it be better to eat one large meal and then sleep or would they be more like sharks and constantly on the move)
One animal species that does exist in this world, but not the Sahara, is a creature similar to a Bantha from Star Wars. They'd be furry animals comparable to yaks in size, but relating more to elephants in nature.