Aetosaurus by Kahless28

Aetosaurus ("eagle lizard") is an extinct genus of archosaur reptile belonging to the order Aetosauria. It is generally considered to be the most primitive aetosaur.[1] Three species are currently recognized: A. ferratus, the type species from Germany and Italy;[2] A. crassicauda from Germany;[3] and A. arcuatus from eastern North America. Additional specimens referred to Aetosaurus have been found from South Africa,[4] the Chinle Group of the southwestern United States,[5][6] and the Fleming Fjord Formation of Greenland.[7] Specimens of Aetosaurus occur in Norian-age strata. It was a late Triassic herbivore. It used to make nests to lay its eggs. Aetosaurs ranged from less than 1 to 4 or 5 meters in length and usually were between 2.5 and 3 meters in length. For archosaurs they were very heavily armored. The armored plates were rectangular shape and appeared flat. Many Aetosaurs are seen with heavy and large bony plates and sometimes they are outfitted with spikes but it depends on the species. For example, The Aetosaurus arcuatus appears to be lacking the large spikes, therefore it has a well protected back but no spikes. This may have made some species of Aetosaurs (arcuatus included) rely a little bit more on speed while others with spikes and heavier scutes relied more on body armor then speed. This is useful in regions (such as Northeastern america) because there were ambush predators such as the Phytosaur Rutiodon and pack predators like Podokesaurus, and speed would likely have helped select Aetosaurs escape predation. Different ecosystems (but mostly wildlife) certainly influenced the evolution of different Aetosaurs. 

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