|Fossil Range|| Late Jurassic - |
Late Cretaceous (Ceratosauridae: 155-80 mya, Abelisauridae: 170-65 mya, Noasauridae: 110-65 mya)
The Ceratosauria group is defined as a grouping of all theropoda dinosaurs who share a more recent common ancestry with ceratosaurs, rather than with birds. As this definition is rather loose, there is no universally agreed upon listing of species under ceratosauria, nor are there true diagnostic characteristics of the group. The only typical identification marker used in identifying species as ceratosaurids are that the classified species are less evolved anatomically, than the more diverse Tetanurae.
The latest, and most accepted, theory identifies ceratosaurian members as Late Jurassic to Late Cretaceous theropods found primarily, although not exclusively, in the Southern Hemisphere, such as Ceratosaurus, Elaphrosaurus and Abelisaurus. Originally, in addition to the afore-mentioned dinosaurs, ceratosauria also included the Coelophysoidea, such as the Coelophysis and Dilophosaurus, which implied a much earlier divergence of the ceratosauria group from other theropods. However, recent studies have shown that coelophysoids do not share enough common characteristics with ceratosaurs to form a clade with them, and hence should be excluded from the ceratosauria group. Such analysis also implies that the ceratosaurids are a sister clade to the Tetanurae, who share common traits but feature more advanced evolutionary traits, and hence likely share a common ancestor.