A geometric morphometric study of sex differences in the scapula, humerus and ulna of Chaetophractus villosus (Xenarthra, Dasypodidae)

ACUÑA F.; SIDORKEWICJ, N.S; POPP A.I; CASANAVE E.B

IHERINGIA. SéRIE ZOOLOGIA

FUNDACAO ZOOBOTANICA RIO GRANDE SUL

Lugar: Porto Alegre; Año: 2017 vol. 107

0073-4721

ABSTRACT. Sexual differences in some of the componentsof the pectoral girdle and forelimb of Chaetophractus villosus (Desmarest,1804) were investigated by means of geometric morphometrics. A total of 15scapulae (7 males, 8 females) and 50 humeri-ulnae complexes (24 males, 26females) were examined. No size differences were detected between sexes for anyof the bones, but shape differences were found for the humerus and the ulna thatenhance the in-forces or the related in-levers. Females had a more robusthumerus, with an enlarged deltoid tuberosity, a more spherical head, higher tubercularand epicondylar widths, and more developed supracondylar crests. The ulna of the females was characterised by a more pronounced curvature along its mainaxis, a caudal displacement of the lateral fossa, a longer olecranon, and adeeper trochlear notch. For both bones, the discriminant analysis classifiedcorrectly all the specimens according to their sex. A small percentage of thevariance (5.2% for the humerus; 6.8% for the ulna) was explained by allometry.The morphological traits found for the humerus and ulna of the females suggest an increased structural strength that could result in powerful digging strokes while keeping shoulder and elbow stabilisation, suggesting a fossorial advantage over males.