SCALING OF LIMB PROPORTIONS AND LIMB BONE DIAMETERS IN 3 SPECIES OF CHINESE SNUB-NOSED LANGURS (GENUS RHINOPITHECUS)

In this study, aspects of the structural mechanics of the upper and lo wer limbs of the three Chinese species of Rhinopithecus were examined. Linear regression and reduced major axis (RMA) analyses of natural lo g-transformed data were used to examine the dimensions of limb bones a nd other relationships to body size and locomotion. The results of thi s study suggest that: (1) the allometry exponents of the lengths of lo ng limbs deviate from isometry, being moderately negative, while the s haft diameters (both sagittal and transverse) show significantly posit ive allometry; (2) the sagittal diameters of the tibia and ulna show e xtremely significantly positive allometry - the relative enlargement o f the sagittal, as opposed to transverse, diameters of these bones sug gests that the distal segments of the fore- and hindlimbs of Rhinopith ecus experience high bending stresses during locomotion; (3) observati ons of Rhinopithecus species in the field indicate that all species en gage in energetic leaping during arboreal locomotion. The limbs experi ence rapid and dramatic decelerations upon completion of a leap. We su ggest that these occasional decelerations produce high bending stresse s in the distal limb segments and so account for the hypertrophy of th e sagittal diameters of the ulna and tibia.