broadly, their skeleton was similar to earlier sauropods, but with a few key differences. the pelvis (hip area) was slimmer than some sauropods, but the pectoral (chest area) was much wider. this them a uniquely 'wide-gauged' stance: their front legs were wider apart, and usually longer than their hind legs. this can be seen very clearly in the "argentinosaurus". as a result, the fossilised trackways of titanosaurs are broader than other sauropods. their vertebrae (back bones) were solid (not hollowed-out). their spinal column was more flexible, so they were probably more agile than their cousins and better at rearing up.