Radiographic Measurements of the Skull in Mantled Howler Monkeys (Alouatta palliata Gray, 1849)

This study evaluated the development of skull components in sanctuary-housed mantled howler monkeys (Alouatta palliata) across age groups, using measurements taken from plain radiographs (lateral view). Thirteen females and 14 males were evaluated (5 infants [ ≤ 14 months], 15 juveniles [15-28 months], 7 subadults/adults [ ≥ 29 months]). Radiographic measurements of length (L) and height (H) were taken of the masticatory (M) component, respiratory (R) component, craniofacial (CF) complex, facial (F) region, and neurocranium (N). Measurements for infants were significantly smaller than for juveniles, which, in turn, were smaller than for subadults/adults. No significant differences were observed between male and female juvenile mantled howler monkeys, except for facial length (p = 0.0253), which was greater in males. A positive correlation was found between age groups and ML, MH, RL, RH, CFL, NH, NL, FL, and FH measurements, but not between age and NH. Moderate (r = from 0.68 to 0.77) or strong (r ≥ 0.80) correlation was documented between NL and masticatory components, respiratory components, and the facial region. Weak correlation (r = from 0.32 to 0.34) was found between NH and ML, RL, and FL, and no correlation between NH and MH, RH, and FH. In conclusion, the present study provides data that contribute to the characterization of the cranial development in mantled howler monkeys. It also aids clinical monitoring of normal growth, detection of potential nutritional deficiencies, and contributes data for forensic analysis to distinguish ages and sex based on skull measurements.