When in motion, it creates a blurred impression of a dark animal speeding over the ice. It is a rare sight to see this creature as it dashes across the glacier. The rimerunner is, like most of Darwin IV's monopedaliens, a ricochetal saltator, equipped with one powerful leg attached to a complex pelvis. This small species, unlike its ground-dwelling cousins, is not particularly fast, a fact to do with the problems inherent in traveling over ice. Its dark, dorsal markings give it a hooded and somewhat threatening appearance. As it lifts its broad, three-toed foot it shows one adaptation that increases traction upon the ice. The padded sole of its foot is deeply channeled and grooved, and with each footfall the pad expands and grips the ice. Each fold probably possesses some additional microstructure to further enhance traction.