 The ages of individual aetosaurs can be determined by examining their osteoderms . Some isolated osteoderms have been claimed to belong to juvenile aetosaurs based on their size and shape but these hypotheses have often been questioned . For example , juvenile osteoderms of <unk> were later identified as those of the small @-@ bodied pseudosuchian Revueltosaurus ( which is not an aetosaur ) , and juvenile osteoderms of Desmatosuchus have been reinterpreted as those of aetosaur <unk> , which had a relatively small body size at maturity . Studies of the bone structure of paramedian osteoderms indicate that new bone was deposited along the edges of each plate over the course of an aetosaur 's lifetime . This means that lines of arrested growth on the undersides of paramedian osteoderms can be used to determine an individual 's age . Comparing the ages of individual specimens with their total body lengths indicates that aetosaurs increased in length at relatively constant rates , but increased in body mass at different rates depending on whether they had wide bodies like Typothorax or narrow bodies like <unk> . Aetosaurs also seem to have grown more slowly than modern crocodilians . Analysis of the limb bones of aetosaurs indicates that they grew quickly when young and more slowly when adults . This pattern of growth is seen in most other pseudosuchians . 
