Carnotaurus

Carnotaurus dinosaur used to be a theropod dinosaur genus. It is known to have lived in South America during the Late Cretaceous period during 72 to 69.9 million years ago. Carnotaurus sastrei is the only species. It is one of the best-known theropods from the Southern Hemisphere, based on a single well-preserved skeleton. The skeleton was discovered in 1984 in Argentina's Chubut Province, made of rocks from the La Colonia Formation. During the late Cretaceous time period, Carnotaurus was a derivative member of the Abelisauridae, which is a family of large theropods that have occupied a large predatory niche in the southern landmasses of Gondwana. This genus is usually considered as a member of the Brachyrostra, which is a clade of short-snouted forms restricted to South America, within the Abelisauridae.

Brief Introduction Of Carnotaurus

Carnotaurus dinosaur was a bipedal predator that measured 7.5 to 9 metres in length and weighed at least 1.35 tonnes. Carnotaurus was a highly specialised and unusual theropod. It is considered to have had strong horns above the eyes, a peculiar characteristic which is not found in any other carnivorous dinosaur, as well as a very deep skull resting on a powerful neck. Small, vestigial forelimbs and long, thin hind limbs were also characteristics of Carnotaurus. Extensive skin impressions have been preserved on the bones, revealing a mosaic of small, non-overlapping scales of around 5 mm in diameter. Large lumps ran along the animal's sides, interrupting the mosaic, and there were no signs of feathers.

It's possible that the prominent horns and powerful neck were utilised to battle conspecifics. Rival individuals may have fought each other with fast head blows, slow pushes with the upper sides of their skulls, or slamming each other head-on, using their horns as shock absorbers, according to separate studies. Carnotaurus' feeding habits are unknown: some research say it was capable of hunting down very huge food such as sauropods, while others suggest it preyed primarily on tiny creatures. Its brain cavity shows that it has a keen sense of smell, although hearing and vision are less developed. Carnotaurus was likely one of the quickest giant theropods and had well-developed running abilities.

How Were They Found?

An expedition directed by Argentinian palaeontologist José Bonaparte uncovered the lone skeleton (holotype MACN-CH 894) in 1984. The unusual spiny sauropod Amargasaurus was also discovered during this expedition. It was the seventh expedition of the National Geographic Society-sponsored "Jurassic and Cretaceous Terrestrial Vertebrates of South America" project, which began in 1976. Only the posterior two-thirds of the tail, much of the lower leg, and the hind feet have been weathered away, so the skeleton is highly preserved and articulated (still attached). The fused sutures in the braincase revealed that the skeleton belonged to an adult. It was discovered resting on its right side, with the neck bent back over the torso, in a classic death attitude. Surprisingly, it has substantial skin imprints maintained. Because of the importance of these impressions, a second expedition was launched to study the original excavation site, which resulted in the discovery of numerous more skin patches. The left side's snout bones were moved forwards relative to the right side's, the nasal bones were forced upwards, and the premaxilla was pushed rearward onto the nasal bones during fossilisation. The upward curve of the upper jaw was also exacerbated by the deformation. Deformation of the nose was more severe than that of the back of the skull, probably due to the latter's higher stiffness. The upper jaws were less U-shaped than the lower jaws in top or bottom view, resulting in an apparent mismatch. This misalignment is the result of side-to-side deformation that impacted the upper jaws but not the lower jaws, presumably due to the lower jaws' greater joint flexibility.

The skeleton was discovered in Bajada Moreno in the Telsen Department of Chubut Province, Argentina, on a property known as "Pocho Sastre." Preparation was tough and time-consuming since it was embedded in a massive hematite concretion, a particularly hard type of rock. Bonaparte issued a note in 1985 that introduced Carnotaurus sastrei as a new genus and species, as well as a brief description of the skull and lower jaw. Carnotaurus is a generic name derived from the Latin words carno ("flesh") and taurus ("bull"), which means "meat-eating bull" in reference to the animal's bull-like horns. Angel Sastre, the owner of the ranch where the skeleton was discovered, is honoured by the particular name sastrei. In 1990, a thorough description of the entire skeleton was published. Carnotaurus was the second member of the Abelisauridae family to be discovered after Abelisaurus. It was for many years the best-known member of its family, as well as the best-known theropod from the Southern Hemisphere. Similar well-preserved abelisaurids, including as Aucasaurus, Majungasaurus, and Skorpiovenator, were not reported until the twenty-first century, allowing scientists to re-evaluate key features of Carnotaurus' morphology. The holotype skeleton is on exhibit at the Bernardino Rivadavia Museum of Natural Sciences in Argentina, and reproductions can be found in other museums throughout the world. Stephen and Sylvia Czerkas, sculptors, created a life-size Carnotaurus sculpture that was originally on exhibit at the Natural History Museum of Los Angeles County. The museum commissioned this sculpture in the mid-1980s, and it is perhaps the first life restoration of a theropod with correct skin.

When & Where Did They Live?

Carnotaurus was discovered in rocks that were originally ascribed to the upper section of the Gorro Frigio Formation, which was thought to be around 100 million years old (Albian or Cenomanian stage). They were later discovered to belong to the considerably younger La Colonia Formation, which dates from the Campanian and Maastrichtian periods (83.6 to 66 million years ago). Novas gave a smaller time window of 72 to 69.9 million years ago in a 2009 book (lower Maastrichtian stage). As a result, Carnotaurus was the most recent South American abelisaurid discovered. South America was already isolated from both Africa and North America by the Late Cretaceous.

The La Colonia Formation is exposed on the North Patagonian Massif's southern slope. The formation's middle portion contains the majority of vertebrate fossils, including Carnotaurus (called the middle facies association). This section most likely reflects the deposits of an estuarine, tidal flat, or coastal plain environment. The weather would have been seasonal, with periods of dryness and humidity. Ceratodon lungfish, turtles, crocodiles, plesiosaurs, dinosaurs, lizards, snakes, and mammals are among the most commonly collected animals. Alamitophis argentinus is one of the snakes discovered, and it belongs to the Boidae and Madtsoiidae families. At least five taxa of turtles are represented, four from the Chelidae (Pleurodira) family and one from the Meio Laniidae family (Cryptodira). The plesiosaur Sulcusuchus errani of the Polycotylid family is a marine reptile. Reigitherium bunodont, the first record of a South American docodont, and Argentodites coloniensis, probably of Multituberculata, are the only mammals present. It was announced in 2011 that a new enantiornithine bird had been discovered in the La Colonia Formation.

Structural Characteristics of Carnotaurus

The only known carnivorous bipedal animal with horns on the frontal bone is Carnotaurus. The exact purpose of these horns is not known. Several interpretations have centred on its usage in fighting conspecifics or killing prey, while it could also be used in courtship or recognition of members of the same species.

Greg Paul (1988) hypothesised that the horns were butting weapons, and that the small orbita would have reduced the risk of eye injury during combat. Carnotaurus, according to Gerardo Mazzetta and colleagues (1998), used its horns in a similar way to rams. They determined that the neck musculature could absorb the force of two people colliding frontally with their heads at a speed of 5.7 m/s apiece. Several bone traits were considered by Fernando Novas (2009) as adaptations for delivering head knocks. He speculated that the skull's shortness may have sped up head motions by lowering the moment of inertia, while the muscular neck would have allowed for powerful head hits. He also noticed increased rigidity and strength in the spinal column, which he believes evolved to withstand head and neck shocks.

According to other research, rival Carnotaurus did not throw quick head strikes, but instead pushed against each other with the upper edges of their skulls. In 2009, Mazzetta and colleagues proposed that the horns were a technique for distributing compression forces without causing brain injury. The flattened upper edges of the horns, the firmly fused bones of the top of the skull, and the skull's incapacity to withstand fast head strikes all support this theory. The horns could have been utilised in slow headbutting and shoving, as seen in the current marine iguana, or in strikes to the opponent's neck and flanks, as shown in the modern giraffe, according to Rafael Delcourt in 2018. In a 2011 conference paper, the latter scenario was advocated for the related Majungasaurus.

The horns may have also been employed to hurt or kill small prey, according to Gerardo Mazzetta and colleagues (1998). Though horn cores are blunt, if a keratinous covering was present, they may have had a comparable shape to modern bovid horns. However, this is the only known instance of animals' horns being used as hunting weapons.

Mazzetta and colleagues' analyses of Carnotaurus' jaw shape in 1998, 2004, and 2009 reveal that the animal was capable of fast bites but not forceful ones. Studies of modern-day crocodiles reveal that quick bites are more crucial than forceful bites when grabbing small prey. These researchers also discovered that the skull, particularly the lower jaw, had a great degree of flexibility (kinesis), similar to that of modern snakes. Carnotaurus' jaw's elasticity would have allowed it to swallow small prey items whole. The front section of the lower jaw was also hinged, allowing it to move up and down. The teeth would have projected forward when pressed downwards, allowing Carnotaurus to spike small prey items; when curled upwards, the now backward projecting teeth would have prevented the captured prey from fleeing. Mazzetta and colleagues also discovered that the skull can endure stresses similar to those experienced when pulling on huge prey objects. Carnotaurus may have preyed primarily on tiny prey, but was also capable of hunting huge dinosaurs. Mazzetta and colleagues calculated a biting force of 3,341 newtons in 2009.

François Therrien and colleagues (2005) questioned this view, finding that Carnotaurus' biting force was double that of the American alligator, which may have the strongest bite of any living tetrapod. The flexural strength of the lower jaw declines linearly towards the tip in modern Komodo dragons, showing that the jaws were not adapted for high precision capture of small prey but for inflicting slashing wounds to weaken large animals. As a result, Carnotaurus must have mostly preyed on huge animals, possibly by ambush, according to this study. Cerroni and colleagues stated in 2020 that the lower jaw's flexibility was limited, and that the thicker skull roof and ossification of multiple cranial joints indicate that the skull had no or little kinesis.

Carnotaurus, according to Robert Bakker (1998), ate mostly very huge prey, particularly sauropods. As he pointed out, various skull adaptations—the short nose, small teeth, and robust back of the skull (occiput)—had developed independently in Allosaurus. These characteristics show that the upper jaw was employed as a serrated club to inflict wounds; repeated blows would have crippled large sauropods.

Cerroni and Paulina-Carabajal studied the endocranial cavity, which included the brain, using a CT scan in 2019. The endocranial cavity had a volume of 168.8 cm3, yet the brain would have only occupied a small portion of it. The researchers employed two different brain size estimates, assuming that the brain occupies 50% and 37% of the endocranial cavity, respectively. This results in a reptile encephalization quotient (intelligence measure) that is higher than that of the closely related Majungasaurus but lower than that of tyrannosaurids. A modest dural expansion – an area on top of the forebrain where the pineal gland is supposed to have been placed – suggests that the pineal gland, which generates hormones, was smaller than in other abelisaurids.

The olfactory bulbs, which housed the sense of smell, were enormous, and the optic lobes, which handled vision, were small. This suggests that in ancient birds, the sense of smell was more developed than the sense of sight, whereas in modern birds, the converse is true. The front end of the olfactory tracts and bulbs were bent downwards, a trait shared exclusively by Indosaurus; similar organs were positioned horizontally in other abelisaurids. This downward-curvature, combined with the huge size of the bulbs, may imply that Carnotaurus relied more on the sense of smell than other abelisaurids, as Cerroni and Paulina-Carabajal hypothesised. Carnotaurus and other South American abelisaurids have a big flocculus, a brain region hypothesised to be linked to gaze stability (eye-body coordination). This could indicate that these forms required a lot of fast head and body movements. The small lagena of the inner ear suggests that Carnotaurus and other abelisaurids' hearing was underdeveloped. It was believed that the hearing range was below 3 kHz.