The theropod (meaning "beast-footed") dinosaurs are a diverse group of bipedal dinosaurs. They include the largest terrestrial carnivores ever to have lived, as well as many quite small species. Theropods typically share a number of traits, including hollow, thin-walled bones and modifications of the hands and feet (three main fingers on the hand, and three main (weight-bearing) toes on the foot). Most theropods had sharp, recurved teeth for eating flesh, and claws on the ends of all of the fingers and toes. Some of these characters were lost or modified in some groups later in theropod evolution. Theropod fossils are fairly rare and often fragmentary. Fossils of small theropods are especially rare, since small bones are harder to find and are weathered away easily.