Dune Diggers

In the shallow sand seas and the deeper dunes of The Giovan Dunes (Region), there exists a species of burrowing worms. These worms swim through the sand and soil of the area with ease, and have been known to range far afield. They are not able to burrow through solid stone however, so the Ten Year and Thirty Year mountain ranges tend to keep them from moving too far out of the Giovan region. They are not especially fond of water, and so tend to avoid passing through rivers and lakes if they can avoid it. They can swim, but not in a very graceful way.
Some of the nomadic tribes of the Giovan Dunes have taken to taming and riding these creatures as others would use a horse or camel. Traveling beneath the desert sands is certainly a cooler option during the scorching heat of the day, although any riders need to be appropriately protected against the sand and earth. Entire tribes are able to quickly pack up their dwellings and gear and mount up their steeds to move a herd of the Diggers to where resources are more plentiful.
There are also rumors of a settlement deep in the central deserts west of Mattheo where Dune Diggers are pitted against one another in exciting races. Observers look on from platforms or ride along on their landboats in this grand spectacle. Great deals of money could be had if one could train a Dune Digger to follow their commands. The young and old alike from both the cities and the Nomadic Tribes of the Giovan dunes find the calling of this 'sport' irresistible.
The Dune Diggers are raised in clutches of eggs ranging in size from about ten to a few dozen. They are about a foot long on hatching, and they have do not seem to have a maximum size. When in the wild they can be encountered in herds or as solitary creatures. There are rumors of Digger Leviathans who are larger than any sea or landboat burrowing deep under the sands, none seem to have met these great creatures and lived to tell the tale.
They are omnivorous creatures and can subsist on desert creatures or vegetation easily. They can retain water for many days, and can remain underground for hours at a time before surfacing for air.