,  Mapusaurus ,  Tyrannosaurus rex  and  Carcharodontosaurus . Not including modern birds, the smallest dinosaurs known were about the size of a  crow  or a  chicken . The theropods  Microraptor  and Parvicursor  were both under 0.6 meters (2 ft) in length. Behavior A nesting ground of  Maiasaura  was discovered in 1978. Interpretations of