 The thumb spike is one of the best @-@ known features of Iguanodon . Although it was originally placed on the animal 's nose by Mantell , the complete Bernissart specimens allowed Dollo to place it correctly on the hand , as a modified thumb . ( This would not be the last time a dinosaur 's modified thumb claw would be <unk> ; <unk> , <unk> , and <unk> are examples since the 1980s where an enlarged thumb claw was first put on the foot , as in <unk> . ) 
