Abelisauridae
Encyclopedia
Abelisauridae is a family
(or clade
) of ceratosauria
n theropod dinosaur
s. Abelisaurids thrived during the Cretaceous
Period, on the ancient southern supercontinent
of Gondwana
, and today their fossil
remains are found on the modern continent
s of Africa
and South America
, as well as on the India
n subcontinent
and the island of Madagascar
. Abelisaurids first appear in the fossil record of the early Cretaceous
period (though bones from the middle Jurassic
may belong to abelisaurids), and at least one species (Majungasaurus crenatissimus) survived until the end of the Mesozoic
era 65 million years ago.
Like most theropods, abelisaurids were carnivorous
biped
s. They were characterized by stocky hindlimbs and extensive ornamentation of the skull
bones, with grooves and pits. In many abelisaurids, like Carnotaurus
, the forelimbs are vestigial, the skull is shorter and bony crests grows above the eyes. Most of the known abelisaurids would have been between 5 to 9 meters (17 to 30 ft) in length, from snout to tip of tail. Before becoming well known, fragmentary abelisaurid remains were occasionally misidentified as possible South American tyrannosaurids.
Although skull proportions varied, abelisaurid skulls were generally very tall and often very short. In Carnotaurus, for example, the skull was nearly as tall as it was long. The premaxilla
in abelisaurids was very tall, so the front of the snout was blunt, not tapered as seen in many other theropods.
Two skull bones, the lacrimal
and postorbital
bones, projected into the eye socket
from the front and back, nearly dividing it into two compartments. The eye would have been located in the upper compartment, which was tilted slightly outwards in Carnotaurus, perhaps providing some degree of binocular vision
. The lacrimal and postorbital also met above the eye socket, to form a ridge or brow above the eye.
Sculpturing is seen on many of the skull bones, in the form of long grooves, pits and protrusions. Like other ceratosaurs, the frontal bone
s of the skull roof were fused together. Carnotaurines commonly had bony projections from the skull. Carnotaurus had two pronounced horns, projecting outward above the eyes, while its close relative Aucasaurus had smaller projections in the same area. Majungasaurus
and Rajasaurus
had a single bony horn or dome, projecting upwards from the skull. These projections, like the horns of many modern animals, might have been display
ed for species recognition or intimidation.
and ulna
) were extremely short, only 25% of the length of the upper arm (humerus
) in Carnotaurus and 33% in Aucasaurus. The entire arm was held straight, and the elbow joint was immobile.
As is typical for ceratosaurs, the carnotaurine hand
contained four basic digits. However, it is there that any similarity ends. No wrist bones existed, with the four palm bones (metacarpals) attaching directly to the forearm. There were no finger bones on the first or fourth digits, only one on the second digit and two on the third digit. These two external fingers were extremely short and immobile, and lacked claws.
It is unknown if this peculiar forelimb structure
applies to abelisaurids other than carnotaurines, as their forelimbs have not been discovered. More primitive relatives such as Noasaurus
and Ceratosaurus
had longer, mobile arms with fingers and claws.
and calcaneum (upper ankle bones) fused to each other and to the tibia
, forming a tibiotarsus. The tibia was shorter than the femur
, giving the hindlimb stocky proportions. There were three functional digits on the foot (the second, third, and fourth), while the first digit, or hallux
, did not contact the ground.
and Fernando Novas
coined the name Abelisauridae in 1985 when they described the eponymous Abelisaurus. The name is formed from the family name of Roberto Abel, who discovered Abelisaurus, as well as from the Greek
word σαυρος/sauros meaning 'lizard'. The very common suffix -idae is usually applied to zoological
family names and is derived from the Greek suffix -ιδαι/-idai, which indicates a plural noun.
Abelisauridae is a family in rank-based Linnaean taxonomy
, within the infraorder Ceratosauria and the superfamily Abelisauroidea, which also contains the family Noasauridae
. It has had several definitions in phylogenetic taxonomy. It was originally defined as a node-based taxon
including Abelisaurus, Carnotaurus, their common ancestor and all of its descendants.
Later it was redefined as a stem-based taxon, including all animals more closely related to Abelisaurus (or the more complete Carnotaurus) than to Noasaurus. The node-based definition would not include animals like Rugops
or Ilokelesia
, which are thought to be more basal
than Abelisaurus and would be included by a stem-based definition. Within Abelisauridae is the subgroup Carnotaurinae, and among carnotaurines, Aucasaurus and Carnotaurus are united in Carnotaurini.
), making it difficult to establish defining features
of the skeleton for the family as a whole. However, most are known from at least some skull bones, so known shared features come mainly from the skull.
Many abelisaurid skull features are shared with carcharodontosaurids. These shared features, along with the fact that abelisaurids seem to have replaced carcharodontosaurids in South America, have led to suggestions that the two groups were related. However, no cladistic analysis has ever found such a relationship and, aside from the skull, abelisaurids and carcharodontosaurids are very different, more similar to ceratosaurs and allosauroids
, respectively.
Following is a list of abelisaurid genera by classification and location, assuming a stem-based definition:
FAMILY ABELISAURIDAE
Indosaurus may be a junior synonym of Indosuchus. Some scientists include Xenotarsosaurus
from Argentina and Compsosuchus
from India as basal abelisaurids, while others consider them to be outside Abelisauroidea. The French
Genusaurus
and Tarascosaurus
have also been called abelisaurids but both are fragmentary and may be more basal ceratosaurians.
of the University of Chicago
and several colleagues, obtained the following results:
Ilokelesia was originally described as a sister group to Abelisauroidea. However, Sereno tentatively places it closer to Abelisaurus than to noasaurids, a result which agrees with several other recent analyses. If a stem-based definition is used, Ilokelesia and Rugops are therefore basal abelisaurids. However, as they are more basal than Abelisaurus, they are outside of Abelisauridae if the node-based definition is adopted. Ekrixinatosaurus was also published in 2004, so it was not included in Sereno's analysis. However, an independent analysis, performed by Jorge Calvo and colleagues, shows it to be an abelisaurid.
With the description of Skorpiovenator
in 2008, Canale et al. published another phylogenetic analysis focusing on the South American abelisaurids. In their results, they found that all South American forms (including Ilokelesia) grouped together as a sub-clade of carnotaurines, which they named Brachyrostra.
of Madagascar. Abelisaurid remains have only been found in the southern continents, which once made up the supercontinent
of Gondwana
. When first described in 1985, only Carnotaurus and Abelisaurus were known, both from the Late Cretaceous
of South America
. Abelisaurids were then located in Late Cretaceous
India
(Indosuchus and Rajasaurus) and Madagascar
(Majungasaurus), which were closely connected for much of the Cretaceous. It was thought that the absence of abelisaurids from continental Africa
indicated that the group evolved
after the separation of Africa from Gondwana, around 100 million years ago. However, the discovery of Rugops and other abelisaurid material from the middle of the Cretaceous in northern Africa disproved this hypothesis. Mid-Cretaceous abelisaurids are now known from South America as well, showing that the group existed prior to the breakup of Gondwana.
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
(or clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
) of ceratosauria
Ceratosauria
Ceratosaurs are members of a group of theropod dinosaurs defined as all theropods sharing a more recent common ancestry with Ceratosaurus than with birds. There is presently no universally agreed upon listing of species or diagnostic characters of Ceratosauria, though they were less derived...
n theropod 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...
s. Abelisaurids thrived during the Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
Period, on the ancient southern supercontinent
Supercontinent
In geology, a supercontinent is a landmass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today.-History:...
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,...
, and today their fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
remains are found on the modern continent
Continent
A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...
s of Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
and 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...
, as well as on the India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
n subcontinent
Subcontinent
A subcontinent is a large, relatively self-contained landmass forming a subdivision of a continent. By dictionary entries, the term subcontinent signifies "having a certain geographical or political independence" from the rest of the continent, or "a vast and more or less self-contained subdivision...
and the island of Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
. Abelisaurids first appear in the fossil record of the early Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
period (though bones from the middle Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
may belong to abelisaurids), and at least one species (Majungasaurus crenatissimus) survived until the end of the Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
era 65 million years ago.
Like most theropods, abelisaurids were carnivorous
Carnivore
A carnivore meaning 'meat eater' is an organism that derives its energy and nutrient requirements from a diet consisting mainly or exclusively of animal tissue, whether through predation or scavenging...
biped
Biped
Bipedalism is a form of terrestrial locomotion where an organism moves by means of its two rear limbs, or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning "two feet"...
s. They were characterized by stocky hindlimbs and extensive ornamentation of the skull
Skull
The skull is a bony structure in the head of many animals that supports the structures of the face and forms a cavity for the brain.The skull is composed of two parts: the cranium and the mandible. A skull without a mandible is only a cranium. Animals that have skulls are called craniates...
bones, with grooves and pits. In many abelisaurids, like Carnotaurus
Carnotaurus
Carnotaurus was a large predatory dinosaur. Only one species, Carnotaurus sastrei has been described so far.Carnotaurus lived in Patagonia, Argentina during the Campanian or Maastrichtian stage of the Late Cretaceous...
, the forelimbs are vestigial, the skull is shorter and bony crests grows above the eyes. Most of the known abelisaurids would have been between 5 to 9 meters (17 to 30 ft) in length, from snout to tip of tail. Before becoming well known, fragmentary abelisaurid remains were occasionally misidentified as possible South American tyrannosaurids.
Skull
Premaxilla
The incisive bone is the portion of the maxilla adjacent to the incisors. It is a pair of small cranial bones at the very tip of the jaws of many animals, usually bearing teeth, but not always. They are connected to the maxilla and the nasals....
in abelisaurids was very tall, so the front of the snout was blunt, not tapered as seen in many other theropods.
Two skull bones, the lacrimal
Lacrimal bone
The lacrimal bone, the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders.-Lateral or orbital surface:...
and postorbital
Postorbital
The postorbital is one of the bones in vertebrate skulls which forms a portion of the dermal skull roof and, sometimes, a ring about the orbit. Generally, it is located behind the postfrontal and posteriorly to the orbital fenestra. In some vertebrates, the postorbital is fused with the postfrontal...
bones, projected into the eye socket
Orbit (anatomy)
In anatomy, the orbit is the cavity or socket of the skull in which the eye and its appendages are situated. "Orbit" can refer to the bony socket, or it can also be used to imply the contents...
from the front and back, nearly dividing it into two compartments. The eye would have been located in the upper compartment, which was tilted slightly outwards in Carnotaurus, perhaps providing some degree of 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...
. The lacrimal and postorbital also met above the eye socket, to form a ridge or brow above the eye.
Sculpturing is seen on many of the skull bones, in the form of long grooves, pits and protrusions. Like other ceratosaurs, the frontal bone
Frontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
s of the skull roof were fused together. Carnotaurines commonly had bony projections from the skull. Carnotaurus had two pronounced horns, projecting outward above the eyes, while its close relative Aucasaurus had smaller projections in the same area. 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...
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...
had a single bony horn or dome, projecting upwards from the skull. These projections, like the horns of many modern animals, might have been display
Display (zoology)
Display is a form of animal behaviour, linked to survival of the species in various ways. One example of display used by some species can be found in the form of courtship, with the male usually having a striking feature that is distinguished by colour, shape or size, used to attract a female...
ed for species recognition or intimidation.
Forelimbs and hands
The forelimbs are known only in the carnotaurine abelisaurids Aucasaurus, Carnotaurus, and Majungasaurus. All had forelimbs which were vestigial. The bones of the forearm (radiusRadius (bone)
The radius is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna, which exceeds it in length and size. It is a long bone, prism-shaped and slightly curved longitudinally...
and ulna
Ulna
The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form and runs parallel to the radius, which is shorter and smaller. In anatomical position The ulna is one of the two long bones in the forearm, the other being the radius. It is prismatic in form...
) were extremely short, only 25% of the length of the upper arm (humerus
Humerus
The humerus is a long bone in the arm or forelimb that runs from the shoulder to the elbow....
) in Carnotaurus and 33% in Aucasaurus. The entire arm was held straight, and the elbow joint was immobile.
As is typical for ceratosaurs, the carnotaurine hand
Manus (zoology)
The manus is the zoological term for the distal portion of the fore limb of an animal. In tetrapods, it is the part of the pentadactyl limb that includes the metacarpals and digits . During evolution, it has taken many forms and served a variety of functions...
contained four basic digits. However, it is there that any similarity ends. No wrist bones existed, with the four palm bones (metacarpals) attaching directly to the forearm. There were no finger bones on the first or fourth digits, only one on the second digit and two on the third digit. These two external fingers were extremely short and immobile, and lacked claws.
It is unknown if this peculiar forelimb structure
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
applies to abelisaurids other than carnotaurines, as their forelimbs have not been discovered. More primitive relatives such as Noasaurus
Noasaurus
Noasaurus is the name given to a carnivorous dinosaur genus of the late Campanian-Maastrichtian...
and Ceratosaurus
Ceratosaurus
Ceratosaurus meaning "horned lizard", in reference to the horn on its nose , was a large predatory theropod dinosaur from the Late Jurassic Period , found in the Morrison Formation of North America, in Tanzania and Portugal...
had longer, mobile arms with fingers and claws.
Hind limbs
Abelisaurid hindlimbs were more typical of ceratosaurs, with the astragalusTalus bone
-External links:* *...
and calcaneum (upper ankle bones) fused to each other and to the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
, forming a tibiotarsus. The tibia was shorter than the femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
, giving the hindlimb stocky proportions. There were three functional digits on the foot (the second, third, and fourth), while the first digit, or hallux
Hallux
In tetrapods, the hallux is the innermost toe of the foot. Despite its name it may not be the longest toe on the foot of some individuals...
, did not contact the ground.
Classification
Paleontologists Jose BonaparteJosé 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...
and Fernando Novas
Fernando Novas
Fernando Emilio Novas is an Argentine paleontologist working for the Comparative Anatomy Department of the Bernardino Rivadavia Natural History Argentine Museum in Buenos Aires...
coined the name Abelisauridae in 1985 when they described the eponymous Abelisaurus. The name is formed from the family name of Roberto Abel, who discovered Abelisaurus, as well as from the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
word σαυρος/sauros meaning 'lizard'. The very common suffix -idae is usually applied to zoological
Zoology
Zoology |zoölogy]]), is the branch of biology that relates to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct...
family names and is derived from the Greek suffix -ιδαι/-idai, which indicates a plural noun.
Linnaean taxonomy
Linnaean taxonomy can mean either of two related concepts:# the particular form of biological classification set up by Carl Linnaeus, as set forth in his Systema Naturæ and subsequent works...
, within the infraorder Ceratosauria and the superfamily Abelisauroidea, which also contains the family Noasauridae
Noasauridae
Noasaurids were a group of theropod dinosaurs from the Cretaceous Period . They were generally small in size...
. It has had several definitions in phylogenetic taxonomy. It was originally defined as a node-based taxon
Taxon
|thumb|270px|[[African elephants]] form a widely-accepted taxon, the [[genus]] LoxodontaA taxon is a group of organisms, which a taxonomist adjudges to be a unit. Usually a taxon is given a name and a rank, although neither is a requirement...
including Abelisaurus, Carnotaurus, their common ancestor and all of its descendants.
Later it was redefined as a stem-based taxon, including all animals more closely related to Abelisaurus (or the more complete Carnotaurus) than to Noasaurus. The node-based definition would not include animals like Rugops
Rugops
Rugops is a genus of theropod dinosaur which inhabited what is now Africa approximately 95 million years ago...
or Ilokelesia
Ilokelesia
Ilokelesia is a primitive abelisaur found in 1991, preserved in the layers of the earliest Late Cretaceous of the Río Limay Formation, Neuquén Group, located near Plaza Huincul, Neuquén Province, Argentina. The specimen, consisting of very fragmentary elements of the skull, the axial and the...
, which are thought to be more basal
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
than Abelisaurus and would be included by a stem-based definition. Within Abelisauridae is the subgroup Carnotaurinae, and among carnotaurines, Aucasaurus and Carnotaurus are united in Carnotaurini.
Shared characteristics
Complete skeletons have been described only for the most advanced abelisaurids (such as Carnotaurus and AucasaurusAucasaurus
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...
), making it difficult to establish defining features
Synapomorphy
In cladistics, a synapomorphy or synapomorphic character is a trait that is shared by two or more taxa and their most recent common ancestor, whose ancestor in turn does not possess the trait. A synapomorphy is thus an apomorphy visible in multiple taxa, where the trait in question originates in...
of the skeleton for the family as a whole. However, most are known from at least some skull bones, so known shared features come mainly from the skull.
Many abelisaurid skull features are shared with carcharodontosaurids. These shared features, along with the fact that abelisaurids seem to have replaced carcharodontosaurids in South America, have led to suggestions that the two groups were related. However, no cladistic analysis has ever found such a relationship and, aside from the skull, abelisaurids and carcharodontosaurids are very different, more similar to ceratosaurs and allosauroids
Allosauroidea
Allosauroidea is a superfamily or clade of theropod dinosaurs which contains four families — the Sinraptoridae, Allosauridae, Carcharodontosauridae, and Neovenatoridae...
, respectively.
Taxonomy
FAMILY ABELISAURIDAE
- AbelisaurusAbelisaurusAbelisaurus is a genus of abelisaurid theropod dinosaur from the Late Cretaceous Period of what is now South America. It was a bipedal carnivore that probably reached 7 to 9 meters in length, although it is known from only one partial skull.The generic name recognizes Roberto Abel as the...
(ArgentinaArgentinaArgentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
) - IndosaurusIndosaurusIndosaurus is a genus of theropod dinosaur once living in what is now India. It lived approximately 69 million years ago, in the Maastrichtian division of the Late Cretaceous...
(India) - IndosuchusIndosuchusIndosuchus is a genus of abelisaurid dinosaur from the Late Cretaceous Period , a theropod related to Abelisaurus. Like most theropods, Indosuchus was a bipedal carnivore...
(India) - KryptopsKryptopsKryptops is a genus of abelisaurid theropod dinosaur from the Early Cretaceous of Niger. It is known from a partial skeleton found at the Gadoufaoua locality in the western Ténéré Desert, in rocks of the Aptian-Albian age Elrhaz Formation...
(NigerNigerNiger , officially named the Republic of Niger, is a landlocked country in Western Africa, named after the Niger River. It borders Nigeria and Benin to the south, Burkina Faso and Mali to the west, Algeria and Libya to the north and Chad to the east...
) - PycnonemosaurusPycnonemosaurusPycnonemosaurus is a genus of carnivorous theropod dinosaur that belonged to the family Abelisauridae. It was found in the Upper Cretaceous Bauru-type red conglomerate sandstone, in the Mato Grosso, in Brazil and lived about 70 million years ago, during the Late Cretaceous .Thus far, fossil...
(BrazilBrazilBrazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
) - RugopsRugopsRugops is a genus of theropod dinosaur which inhabited what is now Africa approximately 95 million years ago...
(Niger) - VitakridrindaVitakridrindaVitakridrinda is a genus of abelisaurid theropod dinosaur from the Late Cretaceous of Balochistan, western Pakistan. The type species is V. sulaimani. The discovery was made near Vitariki by a team of palaeontologists from the Geological Survey of Pakistan,in rocks from the Maastrichtian-age...
(PakistanPakistanPakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
) - XenotarsosaurusXenotarsosaurusXenotarsosaurus is a genus of abelisaurid theropod dinosaur that lived during the Late Cretaceous of Argentina.In 1980 geologist Juan Carlos Sciutto discovered a rich fossil site six kilometres north of the Ocho Hermanos ranch in Chubut province. Among the fossils found there were some theropod...
(Argentina) - Subfamily CarnotaurinaeCarnotaurinaeCarnotaurinae is a subfamily of the theropod dinosaur family Abelisauridae. It includes the dinosaurs Aucasaurus , Carnotaurus , Majungasaurus , and Rajasaurus...
Indosaurus may be a junior synonym of Indosuchus. Some scientists include Xenotarsosaurus
Xenotarsosaurus
Xenotarsosaurus is a genus of abelisaurid theropod dinosaur that lived during the Late Cretaceous of Argentina.In 1980 geologist Juan Carlos Sciutto discovered a rich fossil site six kilometres north of the Ocho Hermanos ranch in Chubut province. Among the fossils found there were some theropod...
from Argentina and Compsosuchus
Compsosuchus
Compsosuchus is an extinct genus of abelisaurian dinosaur. It lived during the Late Cretaceous. It lived in India. Compsosuchus was described in 1933 by von Huene and Matley. The type species is C. solus. The genus is often considered a nomen dubium.-References:* at Dino Russ's Lair...
from India as basal abelisaurids, while others consider them to be outside Abelisauroidea. The French
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
Genusaurus
Genusaurus
Genusaurus is a genus of dinosaur from the Early Cretaceous. Its fossils were found in France. Scientists have estimated the length of Genusaurus to have been 3 m and its weight 50 kg...
and Tarascosaurus
Tarascosaurus
Tarascosaurus is a genus of, perhaps abelisaurid, theropod dinosaur from Late Cretaceous of France.After having in 1988 identified an upper jaw bone found near Pourcieux as belonging to a member of the Abelisauridae, French paleontologist Eric Buffetaut reviewed the known remains of larger...
have also been called abelisaurids but both are fragmentary and may be more basal ceratosaurians.
Phylogeny
A 2004 phylogenetic analysis, performed by Paul SerenoPaul Sereno
Paul Callistus Sereno is an American paleontologist from the University of Chicago who discovered several new dinosaur species on several continents. He has conducted excavations at sites as varied as Inner Mongolia, Argentina, Morocco, and Niger...
of the University of Chicago
University of Chicago
The University of Chicago is a private research university in Chicago, Illinois, USA. It was founded by the American Baptist Education Society with a donation from oil magnate and philanthropist John D. Rockefeller and incorporated in 1890...
and several colleagues, obtained the following results:
Ilokelesia was originally described as a sister group to Abelisauroidea. However, Sereno tentatively places it closer to Abelisaurus than to noasaurids, a result which agrees with several other recent analyses. If a stem-based definition is used, Ilokelesia and Rugops are therefore basal abelisaurids. However, as they are more basal than Abelisaurus, they are outside of Abelisauridae if the node-based definition is adopted. Ekrixinatosaurus was also published in 2004, so it was not included in Sereno's analysis. However, an independent analysis, performed by Jorge Calvo and colleagues, shows it to be an abelisaurid.
With the description of Skorpiovenator
Skorpiovenator
Skorpiovenator is a genus of abelisaurid theropod dinosaur from the late Cretaceous period of Argentina.The type species, Skorpiovenator bustingorryi, is known from a single, nearly complete skeleton missing only most of the forelimbs and parts of the tail...
in 2008, Canale et al. published another phylogenetic analysis focusing on the South American abelisaurids. In their results, they found that all South American forms (including Ilokelesia) grouped together as a sub-clade of carnotaurines, which they named Brachyrostra.
Distribution
Abelisauroids are typically regarded as a Cretaceous group, although possible abelisauroid remains are known from the Middle JurassicJurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
of Madagascar. Abelisaurid remains have only been found in the southern continents, which once made up the supercontinent
Supercontinent
In geology, a supercontinent is a landmass comprising more than one continental core, or craton. The assembly of cratons and accreted terranes that form Eurasia qualifies as a supercontinent today.-History:...
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,...
. When first described in 1985, only Carnotaurus and Abelisaurus were known, both from 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...
of 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...
. Abelisaurids were then located in Late Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
(Indosuchus and Rajasaurus) and Madagascar
Madagascar
The Republic of Madagascar is an island country located in the Indian Ocean off the southeastern coast of Africa...
(Majungasaurus), which were closely connected for much of the Cretaceous. It was thought that the absence of abelisaurids from continental Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
indicated that the group evolved
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
after the separation of Africa from Gondwana, around 100 million years ago. However, the discovery of Rugops and other abelisaurid material from the middle of the Cretaceous in northern Africa disproved this hypothesis. Mid-Cretaceous abelisaurids are now known from South America as well, showing that the group existed prior to the breakup of Gondwana.