Carnotaurus
Encyclopedia
Carnotaurus
Carnotaurus (icon; 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 America
n dinosaurs.
s), depending on the method of estimation. The most distinctive features of Carnotaurus are the two thick horn
s above the eye
s, and the extremely reduced forelimbs with four basic digits, 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. It is also characterized by its unusually long neck (compared to other abelisaur
s), 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.
A single nearly complete skeleton has been described including impressions of skin
along almost the entire right side, that show Carnotaurus lacked feather
s, 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.
, Argentina in 1985 by paleontologist Joseph F. Bonaparte. 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.
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.
Cladogram
of Abelisauridae
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
. 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
. 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.
; Carnotaurus may have been capable of making hatchet-like attacks with its head. Robert Bakker suggests that the upper jaw was used like a club. 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. This suggests that Carnotaurus swallowed small prey whole. Bakker suggests that the allosaur-like adaption of the skull made it capable of preying on large sauropods. 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, and studies of its tail suggest it could have been the fastest dinosaur ever, with a top speed of over 50 km/h (31.1 mph). 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. One study suggested that the expaxial musculature of Carnotaurus could have had a shock-absorbing function as in modern butting mammals. A later study found the skull could not have survived use of the horns for butting. Another suggested function of the horns is to injure or kill small prey.
Carnotaurus (icon; meaning "meat-eating bull", referring to its distinct bull-like horns (Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
caro [carnis] = flesh + taurus = bull) was a large predatory dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
. Only one species, Carnotaurus sastrei has been described so far.
Carnotaurus lived in Patagonia
Patagonia
Patagonia is a region located in Argentina and Chile, integrating the southernmost section of the Andes mountains to the southwest towards the Pacific ocean and from the east of the cordillera to the valleys it follows south through Colorado River towards Carmen de Patagones in the Atlantic Ocean...
, Argentina (La Colonia Formation
La Colonia Formation
The La Colonia Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation....
) during the Campanian
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
or Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
stage of the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
. It was discovered by José Bonaparte
José Bonaparte
José Fernando Bonaparte, Ph.D. , is an Argentine paleontologist who discovered a plethora of South American dinosaurs and mentored a new generation of Argentine paleontologists like Rodolfo Coria...
, who has uncovered many other South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
n dinosaurs.
Description
Carnotaurus was a large theropod, about 8 metres (26.2 ft) in length, weighing between 1488 kg and 2626 kg (1.6–2.9 short tonShort ton
The short ton is a unit of mass equal to . In the United States it is often called simply ton without distinguishing it from the metric ton or the long ton ; rather, the other two are specifically noted. There are, however, some U.S...
s), depending on the method of estimation. The most distinctive features of Carnotaurus are the two thick horn
Horn (anatomy)
A horn is a pointed projection of the skin on the head of various animals, consisting of a covering of horn surrounding a core of living bone. True horns are found mainly among the ruminant artiodactyls, in the families Antilocapridae and Bovidae...
s above the eye
Eye
Eyes are organs that detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptors in conscious vision connect light to movement...
s, and the extremely reduced forelimbs with four basic digits, 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. It is also characterized by its unusually long neck (compared to other abelisaur
Abelisaur
Abelisaurs were a group of ceratosaurian dinosaurs which lived in the Southern hemisphere during the Cretaceous period. Some well-known dinosaurs of this group include Abelisaurus, Carnotaurus, and Majungasaurus. They are known for their small arms...
s), 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
Binocular vision
Binocular vision is vision in which both eyes are used together. The word binocular comes from two Latin roots, bini for double, and oculus for eye. Having two eyes confers at least four advantages over having one. First, it gives a creature a spare eye in case one is damaged. Second, it gives a...
and depth perception
Depth perception
Depth perception is the visual ability to perceive the world in three dimensions and the distance of an object. Depth sensation is the ability to move accurately, or to respond consistently, based on the distances of objects in an environment....
.
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.
A single nearly complete skeleton has been described including impressions of skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
along almost the entire right side, that show Carnotaurus lacked feather
Feather
Feathers are one of the epidermal growths that form the distinctive outer covering, or plumage, on birds and some non-avian theropod dinosaurs. They are considered the most complex integumentary structures found in vertebrates, and indeed a premier example of a complex evolutionary novelty. They...
s, unlike the more advanced coelurosaurian theropods (see also feathered dinosaurs
Feathered dinosaurs
The realization that dinosaurs are closely related to birds raised the obvious possibility of feathered dinosaurs. Fossils of Archaeopteryx include well-preserved feathers, but it was not until the early 1990s that clearly non-avialan dinosaur fossils were discovered with preserved feathers...
). Instead, the skin is lined with rows of bumps, which become larger toward the spine.
Discovery and classifiction
Carnotaurus was found in Chubut ProvinceChubut Province
Chubut a province in the southern part of Argentina situated between the 42nd parallel south and the 46th parallel south , the Andes range separating Argentina from Chile, and the Atlantic ocean...
, Argentina in 1985 by paleontologist Joseph F. Bonaparte. Its remains were in sediments of the La Colonia Formation
La Colonia Formation
The La Colonia Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous. Dinosaur remains are among the fossils that have been recovered from the 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
Campanian
The Campanian is, in the ICS' geologic timescale, the fifth of six ages of the Late Cretaceous epoch . The Campanian spans the time from 83.5 ± 0.7 Ma to 70.6 ± 0.6 Ma ...
-Maastrichtian
Maastrichtian
The Maastrichtian is, in the ICS' geologic timescale, the latest age or upper stage of the Late Cretaceous epoch or Upper Cretaceous series, the Cretaceous period or system, and of the Mesozoic era or erathem. It spanned from 70.6 ± 0.6 Ma to 65.5 ± 0.3 Ma...
), about 75 million years old. The holotype of Carnotaurus sastrei is deposited in the Argentine Museum of Natural Sciences' Bernardino Rivadavia
Bernardino Rivadavia
Bernardino de la Trinidad Gónzalez Rivadavia y Rivadavia was the first president of Argentina, from February 8, 1826 to July 7, 1827 . He was a politician of the United Provinces of Río de la Plata, Argentina today...
, where one can see a replica.
The only species known is C. astrei. Its closest relatives include Aucasaurus
Aucasaurus
Aucasaurus was a genus of medium-sized theropod dinosaur from Argentina that lived during the Santonian stage . It was smaller than the related Carnotaurus, although more derived in some ways, such as its extremely reduced arms and almost total lack of fingers.The type skeleton is complete to the...
(Argentina) Majungasaurus
Majungasaurus
Majungasaurus is a genus of abelisaurid theropod dinosaur that lived in Madagascar from 70 to 65.5 million years ago, at the end of the Cretaceous Period. Only one species has been identified...
(Madagascar), and Rajasaurus
Rajasaurus
Rajasaurus is a genus of carnivorous abelisaurian theropod dinosaur with an unusual head crest. Between 1982 and 1984, its fossilized bones were discovered by Suresh Srivastava of the Geological Survey of India...
(India). These dinosaurs make up the subfamily Carnotaurinae
Carnotaurinae
Carnotaurinae is a subfamily of the theropod dinosaur family Abelisauridae. It includes the dinosaurs Aucasaurus , Carnotaurus , Majungasaurus , and Rajasaurus...
within the family Abelisauridae
Abelisauridae
Abelisauridae is a family of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous Period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are found on the modern continents of Africa and South America, as well as on the Indian...
. 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
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
, replacing the carcharodontosaurids
Carcharodontosauridae
Carcharodontosaurids were a group of carnivorous theropod dinosaurs. In 1931 Ernst Stromer named Carcharodontosauridae as a family, in modern paleontology this name indicates a clade within Carnosauria...
and occupying the ecological niche filled by the tyrannosaurids in the northern continents. In 2008, J. I. Canale et al. proposed a cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
with a focus on carnotaurines from South America.
Cladogram
Cladogram
A cladogram is a diagram used in cladistics which shows ancestral relations between organisms, to represent the evolutionary tree of life. Although traditionally such cladograms were generated largely on the basis of morphological characters, DNA and RNA sequencing data and computational...
of Abelisauridae
Paleoecology
Alamitophis
Alamitophis is a genus of fossil snake in the extinct family of Madtsoiidae. Its length is 80 cm and it fed on frogs, lizards, and small mammals. It is found in Australia and Argentina.-References:*...
. Turtles are represented by at least five taxa, four from Chelidae
Chelidae
The Chelidae are one of the three living families of the turtle suborder Pleurodira and are commonly called the Austro-South American Side Neck turtles. The Family is distributed in Australia, New Guinea, parts of Indonesia and throughout most of South America. It is a large family of turtles with...
(Pleurodira
Pleurodira
The Pleurodira are one of the two living suborders of turtles, the other being the Cryptodira. In many cases in the nomenclature of animals, ranks such as suborder are considered of little importance apart from nomenclatural or taxonomic reasons. However, this is not the case with the suborders of...
) and one from Meiolaniidae
Meiolaniidae
Meiolaniidae is an extinct family of large, possibly herbivorous turtles with heavily armored heads and tails. They are best known from the last surviving genus, Meiolania, which lived in the rainforests of Australia from the Oligocene until the Pleistocene, and relict populations that lived on...
(Cryptodira
Cryptodira
Cryptodira is the taxonomic suborder of Testudines that includes most living tortoises and turtles. Cryptodira differ from Pleurodira in that they lower their necks and pull the heads straight back into the shells; instead of folding their necks sideways along the body under the shells' margins...
). Within the marine fossils in the area is the plesiosaur Sulcusuchus erraini
Sulcusuchus
Sulcusuchus is a genus of polycotylid plesiosaur from the Late Cretaceous of Argentina....
of the family Polycotylidae
Polycotylidae
Polycotylidae is a family of plesiosaurs from the Cretaceous, a sister group to the Leptocleididae.With their short necks and large elongated heads, they resemble the pliosaurs, but closer phylogenetical studies indicate that they share many common features with the plesiosauridae and elasmosauridae...
. Among the mammals in this area is Reigitherium bunodontum
Reigitherium
Reigitherium bunodontum is a mammal that lived during the Late Cretaceous . Fossils of it have been found in the Los Alamitos and the La Colonia Formations of Argentina....
which was considered first record of a South American docodonte
Docodonta
Docodonta is an order of extinct proto-mammals that lived during the mid- to late-Mesozoic era. Their most distinguishing physical features were their relatively sophisticated set of molars, from which the order gets its name. In the fossil record, Docodonta is represented primarily by isolated...
and Argentodites coloniensis, possibly of Multituberculata
Multituberculata
The Multituberculata were a group of rodent-like mammals that existed for approximately one hundred and twenty million years—the longest fossil history of any mammal lineage—but were eventually outcompeted by rodents, becoming extinct during the early Oligocene. At least 200 species are...
. Among dinosaurs, Carnotaurus was contemporary of the iguanodont
Iguanodont
Iguanodonts were herbivorous dinosaurs that lived from the mid-Jurassic to Late Cretaceous. Some members include Camptosaurus, Callovosaurus, Iguanodon, Ouranosaurus, and the hadrosaurids or "duck-billed dinosaurs". Iguanodonts were one of the first groups of dinosaurs to be found...
Talenkauen
Talenkauen
Talenkauen is a genus of basal iguanodont dinosaur from the Maastrichtian-age Upper Cretaceous Pari Aike Formation of Lake Viedma, Santa Cruz, Argentina. It is based on MPM-10001, a partial articulated skeleton missing the rear part of the skull, the tail, and the hands...
and the neovenatorid
Neovenatoridae
Neovenatoridae is a family of large carnivorous dinosaurs. The group is a branch of the allosauroids, a large group of carnosaurs that also includes the sinraptorids, carcharodontosaurids, and allosaurids...
Orkoraptor
Orkoraptor
Orkoraptor is a genus of large theropod dinosaur from the late Cretaceous Period of Argentina. It is known from incomplete fossil remains including parts of the skull, teeth, tail vertebrae, and a partial tibia. The specialized teeth resemble those of some maniraptoriform theropods, namely the...
. 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.
Paleobiology
Analysis of the jaw design of Carnotaurus suggests that the animal was capable of fast-moving bites, but not strong ones. 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 AllosaurusAllosaurus
Allosaurus is a genus of large theropod dinosaur that lived 155 to 150 million years ago during the late Jurassic period . The name Allosaurus means "different lizard". It is derived from the Greek /allos and /sauros...
; Carnotaurus may have been capable of making hatchet-like attacks with its head. Robert Bakker suggests that the upper jaw was used like a club. The skull and lower jaws both have loose sutures between some bones which suggest a high level of cranial kinesis
Cranial kinesis
Cranial kinesis is the term for significant movement of skull bones relative to each other in addition to movement at the joint between the upper and lower jaw. It is usually taken to mean relative movement between the upper jaw and the braincase....
. It appears that Carnotaurus had more mobile joints than any other known dinosaur. This suggests that Carnotaurus swallowed small prey whole. Bakker suggests that the allosaur-like adaption of the skull made it capable of preying on large sauropods. 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, and studies of its tail suggest it could have been the fastest dinosaur ever, with a top speed of over 50 km/h (31.1 mph). 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. One study suggested that the expaxial musculature of Carnotaurus could have had a shock-absorbing function as in modern butting mammals. A later study found the skull could not have survived use of the horns for butting. Another suggested function of the horns is to injure or kill small prey.
External links
- The bite of Carnotaurus at Universidad Nacional de Mar del Plata.
- Gerardo V. Mazzetta, Adrián P. Cisilino & R. Ernesto Blanco.Mandible stress distribution during the bite in Carnotaurus sastrei Bonaparte, 1985 (Theropoda: Abelisauridae). (2004) Ameghiniana 41: 605-617. Buenos Aires.