Why were dinosaurs so successful?

During the Triassic period, over 200 million years ago, dinosaurs established their domination globally even though environmental conditions were exceptionally harsh. Indeed, in resource-poor habitats (i. e. only composed of pine trees and ferns) the foraging success of animal species is minimized due to competition for resources. Moreover, oxygen level was up to 15% (vs. 21% currently). Thanks to comparative anatomy studies, scientists may have found why dinosaurs were so successful during this period. They have compared the anatomy of birds’ respiratory system (i. e. closest relatives to dinosaurs) to dinosaurs’ fossil records, and have found many similar traits: immobile lungs, forked ribs and vertebral pneumaticity (i. e. air spaces within bones). The presence of these structures may indicate that dinosaurs had a thin blood-gas barrier (i. e. membrane over which oxygen is passing through the bloodstream) which facilitated the oxygen diffusion. This implies that dinosaurs had specialized lungs which allowed them to breath in low oxygen environment. To conclude, these specialized lungs conferred to dinosaurs a great adaptive advantage over other animal species which could explain their domination.