The body structure of Dimorphodon displays many "primitive" characteristics, such as, according to Owen, a very small brain-pan and proportionally short wings. The first phalanx in its flight finger is only slightly longer than its lower arm. The neck was short but strong and flexible and may have had a membraneous pouch on the underside. The vertebrae had pneumatic foramina, openings through which the air sacks could reach the hollow interior. Dimorphodon had an adult body length of 1 metre (3.3 ft) long, with a 1.45 metre (4.6 ft) wingspan.