Dinosaurs, the body fossils, are classified into two general groups:  Ornithischians (bird-hip) and Saurischians (lizard-hip).  For dinosaur tracks, however, a different classification scheme is needed since they are trace fossils.  The two dinosaur groups can make similar tracks, therefore, the hip structure is not used as the distinguishing feature.  Instead, the foot prints themselves are used.  The dinosaurs can be divided into those which travel on two feet (bipedal) and those which travel on four feet (quadrupedal).