Carnotaurus is one of the best-understood genera of the Abelisauridae, a family of large theropods restricted to the ancient southern supercontinent Gondwana.
Abelisaurids were the dominant predators in the Late Cretaceous of Gondwana, replacing the carcharodontosaurids and occupying the ecological niche filled by the tyrannosaurids in the northern continents.
Several notable traits that evolved within this family, including shortening of the skull and arms as well as peculiarities in the cervical and caudal vertebrae, were more pronounced in Carnotaurus than in any other abelisaurid.

Though relationships within the Abelisauridae are debated, Carnotaurus is consistently shown to be one of the most derived members of the family by cladistical analyses.
Its nearest relative might have been either Aucasaurus or Majungasaurus; this ambiguity is largely due to the incompleteness of the Aucasaurus skull material.
A recent review suggests that Carnotaurus was not closely related to either Aucasaurus or Majungasaurus, and instead proposed Ilokelesia as its sister taxon.

Carnotaurus is eponymous for two subgroups of the Abelisauridae: the Carnotaurinae and the Carnotaurini.
Paleontologists do not universally accept these groups.
The Carnotaurinae was defined to include all derived abelisaurids with the exclusion of Abelisaurus, which is considered a basal member in most studies.
However, a 2008 review suggested that Abelisaurus was a derived abelisaurid instead.
Carnotaurini was proposed to name the clade formed by Carnotaurus and Aucasaurus; only those paleontologists who consider Aucasaurus as the nearest relative of Carnotaurus use this group.

Below is a cladogram published by Canale and colleagues in 2009.
Carnotaurus is one of the best-understood genera of the Abelisauridae, a family of large theropods restricted to the ancient southern supercontinent Gondwana. Abelisaurids were the dominant predators in the Late Cretaceous of Gondwana, replacing the carcharodontosaurids and occupying the ecological niche filled by the tyrannosaurids in the northern continents. Several notable traits that evolved within this family, including shortening of the skull and arms as well as peculiarities in the cervical and caudal vertebrae, were more pronounced in Carnotaurus than in any other abelisaurid.
Though relationships within the Abelisauridae are debated, Carnotaurus is consistently shown to be one of the most derived members of the family by cladistical analyses. Its nearest relative might have been either Aucasaurus or Majungasaurus; this ambiguity is largely due to the incompleteness of the Aucasaurus skull material. A recent review suggests that Carnotaurus was not closely related to either Aucasaurus or Majungasaurus, and instead proposed Ilokelesia as its sister taxon.
Carnotaurus is eponymous for two subgroups of the Abelisauridae: the Carnotaurinae and the Carnotaurini. Paleontologists do not universally accept these groups. The Carnotaurinae was defined to include all derived abelisaurids with the exclusion of Abelisaurus, which is considered a basal member in most studies. However, a 2008 review suggested that Abelisaurus was a derived abelisaurid instead. Carnotaurini was proposed to name the clade formed by Carnotaurus and Aucasaurus; only those paleontologists who consider Aucasaurus as the nearest relative of Carnotaurus use this group.
Below is a cladogram published by Canale and colleagues in 2009.
Carnotaurus