The carnosaurs (Carnosauria, Greek for “meat-eating lizards”) first appeared in the Middle Jurassic (some say the Late Jurassic) period and lasted until the end of the Cretaceous period. They included the families of Sinraptoridae, Allosauridae, and Carcharodontosauridae, and currently encompass only the allosaurs and their closest kin.

The dinosaurs that made up the carnosaurs were large, heavy predators. In addition to being large in size, these dinosaurs shared other unique characteristics, such as a large cavity in the lacrimal bone of the skull; this cavity, located in front of and above the orbit (eye opening in skull), may have held a gland. Other characteristics included large eye openings in a long, narrow skull, femurs (thigh bones) larger than the tibia (shin bone), and neck vertebrae with a ball joint on the front and a socket on the back. Carnosaurs also had fairly large forelimbs. Some very large carnosaurs in the carcharodontosaurid family (a clade [class] within the Carnisauria), such as Giganotosaurus and Tyrannotitan, are among the largest known predatory dinosaurs ever known.