Aetosauria

Aetosauria is an extinct group of armored crurotarsan reptiles that lived during the Triassic period. They are characterized by their extensive bony armor, or osteoderms, which covered their bodies in a mosaic of scutes, plates, and spines. These herbivores were relatively small to medium-sized, typically ranging from 1 to 6 meters in length. Their armor was their primary defense against predators, with thick plates along their backs and flanks, and often more elaborate spikes or projections on their tails and heads.

Aetosaurs were widespread, with fossils found on most continents. They are known from various Late Triassic deposits, suggesting they were a successful component of Triassic ecosystems. Their diet consisted of plants, and their anatomy, including their relatively small heads and beaks, indicates they were likely low-browsing herbivores. Different aetosaur families and genera are distinguished by variations in the shape, arrangement, and ornamentation of their osteoderms, as well as differences in their skeletal structure.

Fossil evidence suggests they may have lived in terrestrial environments, possibly near freshwater sources. The diversity of aetosaur armor indicates a range of defensive strategies and possibly intraspecific display. Despite their impressive armor, aetosaurs eventually went extinct by the end of the Triassic period, likely succumbing to the major extinction event that marked the transition to the Jurassic. Their lineage represents a significant branch of archosaur evolution that ultimately did not survive into the Mesozoic Era.