 In 1904 , American paleontologist Henry Fairfield Osborn described aetosaurs as carnivorous aquatic animals of the order Parasuchia , mentioning that " [ Parasuchia ] constitutes an independent order , probably freshwater , littoral , carnivorous , short snouted ( Aëtosaurus ) or long snouted ( Phytosaurus , Mystriosuchus ) forms , analogous in their habits to the modern Crocodilia " . Early aetosaur remains were often found in clays beside skeletons of aquatic animals such as phytosaurs and terrestrial animals such as dinosaurs and trilophosaurs . This may have led some paleontologists to believe that the animals had died in swampy environments . Because there were a large number of skeletons of animals that would not normally have inhabited swamps in these clays , some paleontologists even suggested that aetosaurs scavenged off the carcasses of animals that became trapped in the swamps and died . Doubts were later raised over this lifestyle , since aetosaur teeth show little indication of carnivory and the weight of the armor suggests that aetosaurs had " a passive mode of life . " However , aetosaurs were still regarded as partly aquatic into the mid @-@ 20th century . 
