All primates possess some bipedal ability, though most species primarily use quadrupedal locomotion on land. Like other duckbills, it was a bipedal/quadrupedal herbivore. Human walking is about 75% less costly than both quadrupedal and bipedal walking in chimpanzees. They were capable of walking both on two (bipedal) or four (quadrupedal) legs. Raibert's dream is to advance bipedal and quadrupedal robotics to a supernatural state. Most ground locomotion is characterized by quadrupedal knuckle walking. Cattle are large quadrupedal ungulate mammals with cloven hooves. It shares some attributes with giant quadrupedal sauropods like "Apatosaurus". Phalangeriformes are quadrupedal diprotodont marsupials with long tails. "Acanthopholis" was quadrupedal and herbivorous. Like other pterosaurs, "Pteranodon" probably took off from a standing, quadrupedal position. The trunk was short and holds columnar limbs which indicate an obligate quadrupedal posture. As in most quadrupedal ornithischians, its neck is moderately short. "Dimetrodon" was a quadrupedal, sail-backed synapsid. The mountain gorilla is primarily terrestrial and quadrupedal.