To clarify/add to Naina's answer:
As you pointed out, humans do have very different structural differences within the pelvic girdle due to childbirth. Females must have the wide and open pelvic inlet to allow the infant to pass through the birth canal. Whereas males do not bear children, and therefore do not require this structural formation.
However, this type of sexual dimorphism is generally only seen in bipedal humans/animals. Because we are bipedal, we need a short and robust pelvis to bear the weight of our body. So females need the special accommodation of a wide pelvic inlet for childbirth. Quadrapeds (those which have four legs) are oriented horizontally and both male and females have a very elongated pelvis because of this (no need for all the weight to be on the pelvis). There is no need for an additional widening of the pelvis for birth of live young.
If you want a good comparison between male/female humans and male/female animal pelvic sexual dimorphism - any quadraped or non-mammal would be a good pick.
You can probably get a zoological book from the library or just google skeletal images to help explain specific points of comparison
Let us know if you need any further clarification!
M.Sc. Anatomy and Forensic Anthropology