GIGNAC, P.M.*; PRIETO-MARQUEZ, A.; ERICKSON, G.M.; JOSHI, S.H.; Florida State University, Tallahassee; Florida State University, Tallahassee; Florida State University, Tallahassee; Florida State University, Tallahassee: Testing the utility of osteological correlates purported to reflect gender in non-avian dinosaurs
Gender in non-avian theropod dinosaurs has been inferred using attributes in the pelvic girdles and tail skeleton that are presumed to be sexually dimorphic. In theory, wider pelvic canals and shorter, more caudally positioned first chevrons in females act to facilitate the passage of eggs through the cloaca. In contrast longer, more cranially positioned first chevrons in males afford ample attachment area for the �penile retractor� musculature. The American alligator, Alligator mississippiensis, has for the most part served as the model taxon for these sexual phenotypes. Nevertheless, little or no quantitative data has been presented showing that these phenotypes truly exist. Here we used wild-caught skeletons of A. mississippiensis and the squamate Iguana iguana to test whether gender specific morphological differences truly exist in these dinosaurian outgroups. A preliminary sampling of 17 females and 19 males of A. mississippiensis and 13 females and 7 males I. iguana were examined. Measurements of the pelvic canal area, dorsoventral height and mediolateral width of the pelvic canal, height between the dorsal edge of the ilium and the ventral border of the ischium, and lengths and positions of haemal arches 1 and 2 were made. In addition, a new method of shape analysis (Geodesic Distance Analysis) was used to test for morphological differences in the pelvic canal profile. ANCOVA was used to analyze both the data from measurements and the Geodesic Distance Analysis. No significant correlation between sex and pelvic girdle morphology, chevron length, or position was found. Assertions that the gender of dinosaurs can be assessed based upon osteological differences in the pelvic girdles and caudal axial skeleton were not supported.
