Tony: due to their size and nutrient requirements, Dinosaurs would have been incompatible with the advancement of life. Further, the oxygen rich new atmosphere likely would have been toxic to the early flora and fauna. So, after they completed their purpose, they were destroyed to make way for the next step.-You have defined very well some of the aspects of a "balance of nature" that IS required. Animals: oxygen in, CO2 out. Plans: CO2 in, O2 and water out. Perfect, must be present.