 During his re @-@ examination of Iguanodon , David Norman was able to show that this posture was unlikely , because the long tail was stiffened with ossified tendons . To get the tripodal pose , the tail would literally have to be broken . Putting the animal in a horizontal posture makes many aspects of the arms and pectoral girdle more understandable . For example , the hand is relatively immobile , with the three central fingers grouped together , bearing hoof @-@ like phalanges , and able to hyperextend . This would have allowed them to bear weight . The wrist is also relatively immobile , and the arms and shoulder bones robust . These features all suggest that the animal spent time on all fours . 
 During his re @-@ examination of Iguanodon , David Norman was able to show that this posture was unlikely , because the long tail was stiffened with ossified tendons . To get the tripodal pose , the tail would literally have to be broken . Putting the animal in a horizontal posture <a href='uninflect' title='1'><mark>makes</mark></a> many aspects of the arms and pectoral girdle more understandable . For example , the hand <a href='drop_aux' title='2'><mark>is</mark></a>relatively immobile , with the three central fingers grouped together , bearing hoof @-@ like phalanges , and able to hyperextend . This would <a href='been_done' title='3'><mark>have</mark></a> allowed them to bear weight . The wrist <a href='drop_aux' title='4'><mark>is</mark></a>also relatively immobile , and the arms and shoulder bones robust . These features all suggest that the animal spent time on all fours . 
During his re @-@ examination of Iguanodon , David Norman was able to show that dis posture was unlikely , because the long tail was stiffened with ossified tendons . To get the tripodal pose , da tail would literally gotta be broken . Putting the animal in a horizontal posture make many aspects of the arms and pectoral girdle more understandable . For example , tdahand relatively immobile , w/ thdahree central fingers grouped together , bearing hoof @-@ like phalanges , and able to hyperextend . This would done allowed them to bear weight . Thedaist also relatively immobile , and the arms and shoulder bones robust . dese features all suggest that the animal spent time on all fours .