These massive turtle-like creatures move around using a pair of thick, pillar-like forelegs, but most of the weight is carried by an enormous rear skid that leaves a distinctive deep trench in its wake. During a 10-year hibernation period, the 60-foot-high groveback remains largely buried and immobile just beneath Darwin IV's surface. Vegetation takes root and grows on its vast, porous carapace, a bizarre form of symbiosis that gives this behemoth its name. The small forest is shaken off when the animal emerges from dormancy. The large eye-shaped structures behind the nose are actually massive gill books that must be kept moist at all times.

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