You probably didn't know this - here are 9 Birds That Are Secretly Living Dinosaurs Among Us. Many thought dinosaurs were gigantic, slow-moving, cold-blooded reptiles. Dinosaurs can be quick, smart and birdlike. It has been discovered that modern birds did in fact descend from two-legged dinosaurs known as theropods (a group that included feathered velociraptors and tyrannosaurs). Almost all modern-day birds can be traced back to prehistoric creatures. See which birds are most like dinosaurs.