EXTERNAL MONOMORPHISM AND ANATOMICAL DIMORPHISM IN ZAEDYUS PICHIY (XENARTHRA, DASIPODIDAE) FROM MENDOZA PROVINCE (ARGENTINA)

SEITZ, V., CASSINI, G, SUPERINA, M. VIZCAINO, S. F.

Conrad Hotel and Spa, Punta del Este, Uruguay

Congreso; 9th International Congress of Vertebrate Morphology; 2010

International Society of Vertebrate Morphologists

The pichi [Zaedyus pichiy] is an armadillo that inhabits arid and semi-arid habitats of Chile and Argentina, in sandy soils of the Patagonian steppe and Monte Desert, the northern limit of its distribution being Mendoza Province (central west Argentina). No sexual dimorphism was found in morphometric measurements of external features in 204 adult pichis from Mendoza. Nevertheless, sexual dimorphism should be reflected in bony morphology because of the biomechanical demands of partruition. In this contribution, sex-specifc characteristics were examined in a geomorphometric analysis. Three-dimensional landmarks and semi-landmarks were digitized on the ischium, pubis, and ilium of 23 pichis (12 females, 11 males). After procrustes superimposition a Principal Components Analysis was performed. Seven first components contribute to 80% of cumulative variance, 45% being explained by PC1. PC1 clearly separated specimens by sex, with negative values for females and positive for males. Results suggest that females have a greater pelvic cavity than males, indicated by differences in pubic and ischial morphology. In males the ventral joint tips of the left pubis contacts that of the right pubis and they are more anteriorly located than in females, whose tips point more posteriorly and do not contact. The caudo-lateral extremity of the ischium is more enlarged in males. No sexual dimorphism was detected in the ilium. These results indicate that the main differences in pichi pelvic morphology are due to sexual dimorphism, involving the breadth of pelvic cavity associated with the demands of parturition on females.