Sinosauropteryx
"Sinosauropteryx" was a small theropod with an unusually long tail and short arms. The longest known specimen reaches up to in length, with an estimated weight of It was a close relative of the similar but older genus "Compsognathus", both genera belonging to the family Compsognathidae. Only one species of "Sinosauropteryx" has been named: "S. prima", meaning "first" in reference to its status as the first feathered non-avialian dinosaur species discovered. Three specimens have been described. The third specimen previously assigned to this genus represents either a second, as-yet unnamed species or a distinct, related genus.
Giganotosaurus
"Giganotosaurus" is thought to have been one of the largest theropod dinosaurs, but the incompleteness of its remains have made it difficult to estimate its size reliably. It is therefore impossible to determine with certainty whether it was larger than "Tyrannosaurus", for example, which has been considered the largest theropod historically. Different size estimates have been reached by several researchers, based on various methods, and depending on how the missing parts of the skeleton have been reconstructed. Length estimates for the holotype specimen have varied between , with a skull between long, a femur (thigh bone) between long, and a weight between . Fusion of sutures (joints) in the braincase indicates the holotype specimen was a mature individual. A second specimen, consisting of a dentary bone (part of the lower jaw) from a supposedly larger individual, has been used to extrapolate a length of , a skull long, and a weight of . Some writers have considered the largest size estimates for both specimens exaggerated. "Giganotosaurus" has been compared to an oversized version of the well-known genus "Allosaurus".