The pelvis girdle was present in early vertebrates.

http://en.wikipedia.org/wiki/Pelvis

The pelvis girdle was present in early vertebrates, and can be tracked back to the paired fins of fish that were some of the earliest chordates.The shape of the pelvis, most notably the orientation of the iliac crests and shape and depth of the acetabula, reflects the style of locomotion and body mass of an animal.