External monomorphism and anatomical dimorphism in Zaedyus pichiy (Xenarthra, Dasipodidae) from Mendoza Province (Argentina)

SEITZ, VIVIANA PAOLA; CASSINI, GUILLERMO HERNÁN; SUPERINA, MARIELLA; VIZCAÍNO, SERGIO FABIÁN

Punta del Este -Uruguay

Congreso; 9th International Congress of Vertebrate Morphology; 2010

Universidad de La República - International Society of Vetebrate Morphologyst

The pichi (Zaedyus pichiy) inhabit in arid and semi-arid habitats of Chile and Argentina, in sandy soils of Patagonian steppe and Monte Desert, being Mendoza Province (central west Argentina) the northern limit of its distribution. We measured 204 adult pichis from Mendoza and no external sexual dimorphism was found in morphometric measurements. Functionally, different biomechanical demands on parturient females should be reflected in bones morphology. Sexual differences were assigned performing a morphogeometric analysis. Three-dimensional landmarks and semi landmarks were digitalized on ischium, pubis and ilium bones on twenty-three pichis (12 females, 11 males). After a procrustean superposition a Principal Component Analysis was achieved. Seven first components contribute with eighty percent of cumulative variance, being 45% explained by the first component. PC1 presented a clear distribution of specimens by sex, showing negative values for females and positive for males. Results suggest that females have a greater cavum pelvis than males, indicated by differences on pubis and ischium morphology. Males ventral joint-tips of both pubis (left and right) get in contact and are placed more anteriorly than in females, whose tips pointed more posteriorly and do not get in contact. Concerning to the ischium, males have caudo-lateral extremity more enlarged. No differences due to sexual dimorphism were detected in ilium morphology. These results indicate that main differences in pelvis morphology of pichis are attributed to differences between sexes, involving the breadth of pelvic cavity associated to parturiency demands on females.