situated above the caudal ribs would have been proportionally smaller. These muscles, called the longissimus and spinalis muscle, were responsible for tail movement and stability. To maintain tail stability in spite of reduction of these muscles, the caudal ribs bear forward projecting processes interlocking the vertebrae with each other and with the pelvis, stiffening the tail. As a consequence, the ability to make tight turns would have been diminished, because the hip and tail had to be turned simultaneously, unlike in other theropods. Brain and senses Cerroni and Paulina-Carabajal, in 2019, used a CT scan to study the endocranial cavity that contained the brain. The volume of the endocranial cavity was 168.8 cm³, although the brain would only have filled a fraction of this space. The authors used two different brain size estimates, assuming a brain size of 50% and 37% of the endocranial cavity, respectively. This results in a reptile encephalization quotient (a measure of intelligence) larger than that of the related Majungasaurus but smaller than in tyrannosaurids. The pineal gland, which produces hormones, might have been smaller than in other abelisaurids, as indicated by a low dural expansion – a space on top of the forebrain in which the pineal gland is thought to have been located. The olfactory bulbs, which housed the sense of smell, were large, while the optic lobes, which were responsible for sight, were relatively small. This indicates that the sense of smell might have been better developed than the sense of sight, while the opposite is the case in modern birds. The front end of the olfactory tracts and bulbs were curved downwards, a feature only shared by Indosaurus; in other abelisaurids, these structures were oriented horizontally. As hypothesized by Cerroni and Paulina-Carabajal, this downward-curvature, together with the large size of the bulbs, might indicate that Carnotaurus relied more on the sense of smell than other abelisaurids. 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. This could indicate that these forms frequently used quick movements of the head and body. Hearing might have been poorly developed in Carnotaurus and other abelisaurids, as indicated by the short lagena of the inner ear. The hearing range was estimated to be below 3 kHz. Age and paleoenvironment Originally, the rocks in which Carnotaurus was found were assigned to