Why were there no tiny dinosaurs? Mammals may hold the answer

The absence of tiny dinosaurs may be just as interesting as the existence of giant ones. Around 75% of living mammals and 90% of living birds are smaller than the smallest non-avian dinosaurs. “If we want to understand how today’s biodiversity evolved, we need to understand why tiny dinosaurs appear to have been missing.” The fossil record suggests that tiny non-avian dinosaurs would have been extremely rare, or may not have existed. Instead, ecological factors such as predation and competition would have played a large role in how small non-avian dinosaurs could become.