'meat bull') is a genus of theropod dinosaur that lived in South America during the Late Cretaceous period, probably sometime between 72 and 69 million years ago.

It had two thick horns above the eyes, a unique feature unseen in all other carnivorous dinosaurs, and a very deep skull sitting on a muscular neck.

The skeleton is preserved with extensive skin impressions, showing a mosaic of small, non-overlapping scales approximately 5 mm in diameter.

According to separate studies, rivaling individuals may have combated each other with quick head blows, by slow pushes with the upper sides of their skulls, or by ramming each other head-on, using their horns as shock absorbers.

[3] It was the eighth expedition within the project named "Jurassic and Cretaceous Terrestrial Vertebrates of South America", which started in 1976 and was sponsored by the National Geographic Society.

[3][B] The skeleton is well-preserved and articulated (still connected together), with only the posterior two thirds of the tail, much of the lower leg, and the hind feet being destroyed by weathering.

[D] In view of the significance of these impressions, a second expedition was started to reinvestigate the original excavation site, leading to the recovery of several additional skin patches.

[13][14] It was not until the 21st century that similar well-preserved abelisaurids were described, including Aucasaurus, Majungasaurus and Skorpiovenator, allowing scientists to re-evaluate certain aspects of the anatomy of Carnotaurus.

[15] Sculptors Stephen and Sylvia Czerkas manufactured a life-sized sculpture of Carnotaurus that was previously on display at the Natural History Museum of Los Angeles County.

These horns, formed by the frontal bones,[V] were thick and cone-shaped, internally solid, somewhat vertically flattened in cross-section, and measured 15 cm (5.9 in) in length.

The frontmost of these openings, the external naris (bony nostril), was subrectangular and directed sidewards and forwards, but was not sloping in side view as in some other ceratosaurs such as Ceratosaurus.

The lower front corner of the antorbital fossa contained a smaller opening, the promaxillary fenestra, which led into an air-filled cavity within the maxilla.

[AD][26][1] In Carnotaurus, three hyoid bones are preserved: a pair of curved, rod-like ceratobranchials that articulate with a single, trapezoidal element, the basihyal.

[1] The vertebral column consisted of ten cervical (neck), twelve dorsal, six fused sacral[AE] and an unknown number of caudal (tail) vertebrae.

[29] The hand showed four basic digits,[4] though apparently only the middle two of these ended in finger bones, while the fourth consisted of a single splint-like metacarpal that may have represented an external 'spur'.

[7] These impressions, found beneath the skeleton's right side, come from different body parts, including the lower jaw,[7] the front of the neck, the shoulder girdle, and the rib cage.

A hummocky surface with grooves, pits, and small openings is found on the sides and front of the snout and indicates a scaly covering, possibly with flat scales as in today's crocodilians.

The top of the snout was sculptured with numerous small holes and spikes – this texture can probably be correlated with a cornified pad (horny covering).

A row of large scales did probably surround the eye, as indicated by a hummocky surface with longitudinal grooves on the lacrimal and postorbital bones.

The bumps probably represent feature scales – clusters of condensed scutes – similar to those seen on the soft frill running along the body midline in hadrosaurid ("duck-billed") dinosaurs.

The basement scales of Carnotaurus were by comparison highly variable, ranging in size from small and elongated, to large and polygonal, and from circular-to-lenticular in the thoracic, scapular, and tail regions, respectively.

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.

[17] 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.

[AQ] Juan Canale and colleagues, in 2009, erected the new clade Brachyrostra to include Carnotaurus but not Majungasaurus; this classification has been followed by a number of studies since.

[AT] Other studies suggest that rivaling Carnotaurus did not deliver rapid head blows, but pushed slowly against each other with the upper sides of their skulls.

As he noted, several adaptations of the skull—the short snout, the relatively small teeth and the strong back of the skull (occiput)—had independently evolved in Allosaurus.

The flocculus, a brain lobe thought to be correlated with gaze stabilization (coordination between eyes and body), was large in Carnotaurus and other South American abelisaurids.

[24] Originally, the rocks in which Carnotaurus was found were assigned to the upper part of the Gorro Frigio Formation, which was considered to be approximately 100 million years old (Albian or Cenomanian stage).

[5][AV] Later, they were realized to pertain to the much younger La Colonia Formation,[13] dating to the Campanian and Maastrichtian stages (83.6 to 66 million years ago).

[59][60] Mammals are represented by Reigitherium bunodontum and Coloniatherium cilinskii, the former of which was considered the first record of a South American docodont,[54][61] and the possible gondwanatherians or multituberculates Argentodites coloniensis and Ferugliotherium windhauseni.