Why Small Dinosaurs Were Rare: Mammals May Have Been the Reason

Dinosaurs emerged approximately 230 million years ago and went on to dominate land ecosystems across Earth. They maintained this dominance for tens of millions of years before a mass extinction event ended their reign. An asteroid impact 66 million years ago is widely recognized as the trigger for this catastrophic die-off. Researchers have been examining why very small-bodied dinosaurs were notably absent, despite the group's enormous diversity. Mammals are now being considered as a possible factor that may have prevented tiny dinosaurs from establishing themselves in smaller size niches.