The upper surfaces of the front and rear legs are covered in a pale gray coat, and the hind legs are very short and wide. The feet lack small tubercles and the thumb is covered by a nail. Its skull is short and wide, and it has a heavy, large, and uncurved zygomatic bone. The supraorbital ridge of the skull is large, and the interorbital region is very broad with nearly parallel sides. The facial portion of the skull is very short, and the distance between the incisors and the molars is slightly less than the length of the coronary surface of its upper row of teeth. "Santamartamys" has large eyes, which is consistent with its nocturnal behaviour. It has two pairs of udders on the lateral edge of the abdominal side coat.