The front limb is 135 mm and the back limb is 165 mm, giving the reptile a length ratio of almost 1x as long as the dorsal-sacral region. "Petrolacosaurus" also has a zeugopodium in both its front and hind limbs that is longer than the stylopodium. In aquatic reptile species, a shorter zeugopodium and longer stylopodium are characteristic in fins. Both this length relationship and a wide sacral rib in "Petrolacosaurus" are indicative of a sprawled, quadrupedal posture. The elongation of limbs were also adaptations for faster locomotion.