Tyrannosaurus is a genus of coelurosaurian theropod dinosaur. Coelophysidae is a family of primitive carnivorous theropod dinosaurs. Nearly all palaeontologists regard birds as coelurosaurian theropod dinosaurs. Dromaeosauridae is a family of feathered theropod dinosaurs. It is a "nomen dubium", perhaps a theropod or some indeterminate predatory archosaur. The original Carnosauria was a polyphyletic group including any large carnivorous theropod. Many anatomical features are shared by birds and theropod dinosaurs. All early finds of theropod fossils showed them to be primarily carnivorous. This is the first example of tail truncation known in a non-avian theropod dinosaur. Birds themselves are thought to be descendants of theropod dinosaurs. Birds are now recognized as being the sole surviving lineage of theropod dinosaurs. Compsognathidae is a family of coelurosaurian theropod dinosaurs. Troodontidae is a family of bird-like theropod dinosaurs. Noasauridae was a family of diverse theropod dinosaurs from the group Ceratosauria. It is classified as an allosaurid, a type of carnosaurian theropod dinosaur.