| Carnotaurus Temporal range: Late Cretaceous, 75 Ma |
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| Mounted skeletal cast, Chlupáč Museum, Prague | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Superorder: | Dinosauria |
| Order: | Saurischia |
| Suborder: | Theropoda |
| Family: | †Abelisauridae |
| Subfamily: | †Carnotaurinae |
| clade: | †Brachyrostra |
| Tribe: | †Carnotaurini |
| Genus: | †Carnotaurus Bonaparte, 1985 |
| Species: | †C. sastrei |
| Binomial name | |
| Carnotaurus sastrei Bonaparte, 1985 |
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Carnotaurus ( /ˌkɑrnɵˈtɔrəs/; meaning "meat-eating bull", referring to its distinct bull-like horns (Latin caro [carnis] = flesh + taurus = bull) was a large predatory dinosaur. Only one species, Carnotaurus sastrei has been described so far.
Carnotaurus lived in Patagonia, Argentina (La Colonia Formation) during the Campanian or Maastrichtian stage of the Late Cretaceous. It was discovered by José Bonaparte, who has uncovered many other South American dinosaurs.[1]
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Carnotaurus was a large theropod, about 8 metres (26 ft) in length,[2] weighing between 1488 kg and 2626 kg (1.6–2.9 short tons), depending on the method of estimation.[3][4] The most distinctive features of Carnotaurus are the two thick horns above the eyes, and the extremely reduced forelimbs with four basic digits,[3] though only the middle two of these ended in finger bones, while the fourth was splint-like and may have represented an external 'spur.' The fingers themselves were fused and immobile, and lacked claws.[5] It is also characterized by its unusually long neck (compared to other abelisaurs), and its small head with box-shaped jaws. The eyes of Carnotaurus faced forward, which is unusual in a dinosaur, and may indicate binocular vision and depth perception.
There is a rather puzzling contrast between Carnotaurus’ deep, robust-looking skull and its shallow, slender lower jaw. So far no-one has worked out what this might imply about its methods of feeding.[6]
A single nearly complete skeleton has been described including impressions of skin along almost the entire right side, that show Carnotaurus lacked feathers, unlike the more advanced coelurosaurian theropods (see also feathered dinosaurs). Instead, the skin is lined with rows of bumps, which become larger toward the spine.
Carnotaurus was found in Chubut Province, Argentina in 1985 by paleontologist Joseph F. Bonaparte.[1] Its remains were in sediments of the La Colonia Formation. One mostly complete skeleton was found, missing only the distal end of the tail and the last part of the lower limbs. It was an unusual find because of its extensive skin impressions. The specimen was collected at the farm "Pocho Sastre" near Bajada Moreno, Telsen Department, Chubut, Argentina, in sediments corresponding to the lower section of the La Colonia Formation, Late Cretaceous (Campanian-Maastrichtian), about 75 million years old. The holotype of Carnotaurus sastrei is deposited in the Argentine Museum of Natural Sciences' Bernardino Rivadavia, where one can see a replica.[1]
The only species known is C. astrei. Its closest relatives include Aucasaurus (Argentina) Majungasaurus (Madagascar), and Rajasaurus (India). These dinosaurs make up the subfamily Carnotaurinae within the family Abelisauridae. Within the subfamily Carnotaurinae, Carnotaurus and Aucasaurus are more closely related and both genera are placed in the tribe Carnotaurini. Findings show that these 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. In 2008, J. I. Canale et al. proposed a cladogram with a focus on carnotaurines from South America.[7]
| Abelisauridae |
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Cladogram of Abelisauridae
| Carnotaurinae |
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La Colonia Formation is likely the deposits of an environment of estuaries, with low coasts and exchange of inland freshwater with the tidal sea, where there are shellfish and shellfish-like oysters. This portion of the sea is known as the Kawasan Sea as well as the Transgression of Schiller. The most common vertebrates collected include fish, turtles, crocodiles, plesiosaurs, dinosaurs, snakes and mammals. Some snakes found belong to in the families Boidae and Madtsoidae, such as the Alamitophis argentinus.[8] Turtles are represented by at least five taxa, four from Chelidae (Pleurodira) and one from Meiolaniidae (Cryptodira). Within the marine fossils in the area is the plesiosaur Sulcusuchus erraini of the family Polycotylidae. Among the mammals in this area is Reigitherium bunodontum which was considered first record of a South American docodonte and Argentodites coloniensis, possibly of Multituberculata.[9] Among dinosaurs, Carnotaurus was contemporary of the iguanodont Talenkauen and the neovenatorid Orkoraptor. The paleoflora was known for its aquatic components, Paleoazolla and Regnellidium. However, recent paleobotanical discoveries have revealed the presence of a more diverse range of plants associated with these water bodies, including pteridophytes, gymnosperms, and various angiosperms. Among these are the fossils of the fruits of Nelumbonaceae.
Analysis of the jaw design of Carnotaurus suggests that the animal was capable of fast-moving bites, but not strong ones. [10] It appears that the muscles that closed the jaws were important for reducing stresses on the skull during biting; the bite was weaker but faster than that of Allosaurus; Carnotaurus may have been capable of making hatchet-like attacks with its head.[11] Robert Bakker suggests that the upper jaw was used like a club. [12] The skull and lower jaws both have loose sutures between some bones which suggest a high level of cranial kinesis. It appears that Carnotaurus had more mobile joints than any other known dinosaur.[10] This suggests that Carnotaurus swallowed small prey whole.[10] Bakker suggests that the allosaur-like adaption of the skull made it capable of preying on large sauropods.[12] It is also possible that the cranial kinesis of this theropod can maintain an unchanging orientation of the eye with respect to prey. Unlike the skulls of lizards, the skull of Carnotaurus does not have the orbits located on the muzzle region. As such, the skull of Carnotaurus was well adapted for keeping visual contact with its victim. Studies of the femur of Carnotaurus suggest that it was fast and could run down prey,[10] and studies of its tail suggest it could have been the fastest non-avian dinosaur ever, with a top speed of over 50 km/h (31 mph).[13][14] It has been proposed that Carnotaurus used its horns as weapons when fighting conspecifics in a manner similar to rams. There is no evidence of interlocking structures, so it could not spar in a manner similar to deer. [10] One study suggested that the expaxial musculature of Carnotaurus could have had a shock-absorbing function as in modern butting mammals.[10] A later study found the skull could not have survived use of the horns for butting. [11] Another suggested function of the horns is to injure or kill small prey. [10]