Recent studies shed light on size and demise of the dinosaurs

Nature : Two studies in the Royal Society’s Biology Letters examine dinosaurs’ huge size and possible reasons for it. In the first study , Roland Sookias at Ludwig-Maximilians University in Munich and colleagues looked at whether body size depended on environmental factors, such as temperature, oxygen level, and amount of available dry land. They found that biological factors were more important in determining maximum body size. In the second study , Daryl Codron at the University of Zurich in Switzerland and colleagues found that dinosaurs’ size may have depended on the limitations of egg laying. Because the larger the egg, the thicker the shell and the more difficult for a developing embryo to breathe, egg size was limited. That physical limit forced dinosaurs to produce very small young. To compete with other dinosaurs for food, the successful ones grew very big, very fast. Unfortunately, dinosaurs’ vast size proved to be their downfall; the extremely large animals were mostly wiped out by an asteroid impact at the end of the Cretaceous period some 65 million years ago. Birds and small mammals fared better.