 While the skull of Mesopropithecus most closely resembles that of modern sifakas , the postcranial skeleton is quite different . Rather than having elongated hindlimbs for leaping , Mesopropithecus had elongated forelimbs , suggesting they predominantly used quadrupedal locomotion , slow climbing , with some forelimb and hindlimb suspension . In fact , they were the most quadrupedal of the sloth lemurs , having an intermembral index between 97 and 113 , compared to the lower value for indriids and higher values for the other sloth lemurs . ( In arboreal primates , an intermembral index of 100 predicts quadrupedalism , higher values predict suspensory behavior , and lower values predict leaping behavior . ) Wrist bones found in 1999 further demonstrate that Mesopropithecus was a vertical climber and the most loris @-@ like of the sloth lemurs . Analysis of a lumbar vertebra of M. dolichobrachion further supported this conclusion . 
