 Aetosaur fossil remains are known from Europe , North and South America , parts of Africa and India . Since their armoured plates are often preserved and are abundant in certain localities , aetosaurs serve as important Late Triassic tetrapod index fossils . Many aetosaurs had wide geographic ranges , but their stratigraphic ranges were relatively short . Therefore , the presence of particular aetosaurs can accurately date a site that they are found in . 
