During the Mesozoic Era, dinosaurs lived in a climate that was much milder and less changing than the climate today. Areas near the seas, and along rivers and lakes, may have had mild, moist weather all year round. Inland regions were drier and in some cases, desert like. Toward the end of the Reptile Age, the climate grew cooler and the change of seasons became more distinct. It was during these changes that the continents began to break apart into individual land masses.
Plant and animal life also changed during the Mesozoic Era. During the first half of the era, primitive conifers (cone bearing trees) and cycads (palm like trees) were the most common plants. Other land animals inhabiting the earth during this time were crocodilians, frogs, insects, lizards, turtles, and a few other small species. .
During the second half of this period flowering plants started to appear. Scientist believe that birds were developed from small carnivorous dinosaurs. During this entire period, dinosaurs ruled the earth.
People once believed that dinosaurs were clumsy, slow moving, unintelligent creatures that lived much like reptiles. Fossil evidence suggest that some dinosaurs were much more active and intelligent than previously thought. In addition, scientists can learn much about the life of the dinosaurs by studying birds, turtles, and other modern animals that have similarities to dinosaurs. How dinosaurs lived depends greatly on whether they were cold or warm blooded.
Traditionally dinosaurs were considered endothermic, or warm blooded. They point out that many dinosaurs were more active and therefore maintained a more constant body temperature. Other dinosaur features, such as the internal bone structure, and the chemistry of the bone, also suggest that some dinosaurs were warm blooded. .
Scientist are unaware of how all dinosaurs reproduced. Fossil dinosaur eggs suggest that at least some dinosaurs laid hard shelled eggs.