Theropods 1:An enormously successful subgroup of the Saurischia, the bipedal (two-footed) theropods (“beast feet”) emerged 230 million years ago in Late Triassic times; the oldest known example comes from South America. Theropods spanned the age of most dinosaurs (230–65 million years ago) and beyond, and included most of the known predatory dinosaurs. The typical theropod had smallish arms with sharp, clawed fingers; powerful jaws lined with sharp teeth; an S-shaped neck; long, muscular hind limbs; and clawed, usually four-toed feet. Many theropods may have been warm-blooded; most were exclusively carnivorous. Theropods ranged from animals no larger than
a chicken to huge creatures, such as Tyrannosaurus and Baryonyx. The group also included ostrichlike omnivores and herbivores with toothless beaks, such as Struthiomimus and Gallimimus. Birds are dinosaurs and evolved from within a group of tetanuran theropods called maniraptorans.
Archaeopteryx, small and feathered, was the first known bird and lived alongside other dinosaurs.
