The theropods (Theropoda) had many general characteristics. Because they were carnivores, their teeth tended to be blade-like, with serrated ridges. Their claws, especially on the hands, were often recurved and tapered to sharp points. The outer fingers of the hand were either reduced in size or were completely lost. Most theropods were long-legged, bipedal, slender, and quick—all characteristics that enabled the animals to more easily catch their prey. They also had three walking toes on the hind feet.

Theropods had hollow limb bones; some went one step further and had air-filled (pneumatic) bones in certain parts of their body. For example, in some dinosaurs, pneumatic bones were found in the middle of the tail; in others, the air-filled bones were present at the back of the skull.

There is a good deal of evidence that larger theropods attacked other animals. For example, sauropod bones found in Colorado show the bite marks from a large theropod—and sometimes the bones indicate that the prey survived the attack. At other sites, trackways show the footprints of theropods chasing or stalking smaller sauropods.