The Boulderback is a unique beast native to the planet Nexus. It possesses many features common to reptiles, especially shelled creatures such as turtles, but grows to a much larger size that its scaly cousins. They also possess many characteristics reflective of their mostly mineral diet, such as the crystalline growths on their backs that give them their name. Adult boulderbacks can easily grow to the size of a shuttlecraft.
The massive, shelled reptilians called boulderbacks have an unusual diet that is still not entirely understood. They are not carnivores (though they will bite with powerful jaws to defend themselves) and have only rarely been witnessed eating root vegetables. The rest of their diet appears to consist solely of earth and stone, from which their bodies somehow draw enough nutrition to reach truly gigantic size.
Scientists believe the best evidence for this hypothesis is the apparent absence of young boulderbacks on the surface - they must exist somewhere, but only adults are know to emerge from the soil in regions like Algoroc. The most widely accepted hypothesis is that young boulderbacks are born underground and do not emerge at all until they are fully grown.
Aside from the stony shells that give them their name, the most commonly observed feature of the boulderback is the species-wide tendency to burrow partway into the earth to rest, eat, and possibly mate. When boulderbacks do so they are virtually indistinguishable from surrounding rocks and boulders to the untrained eye, and can be quite dangerous to those unprepared for their sudden emergence. It is believe this behavior very early, during the subterranean period of development and growth, and acts as a defensive camouflage for the boulderback. As no natural predators of boulderbacks have ever been observed, however, this theory appears tenuous at best.