Abelisauridae (meaning "Abel's lizards") is a
family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
(or
clade
In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
) of
ceratosauria
Ceratosaurs are members of the clade Ceratosauria, a group of dinosaurs defined as all theropods sharing a more recent common ancestor with '' Ceratosaurus'' than with birds. The oldest known ceratosaur, '' Saltriovenator'', dates to the earlies ...
n
theropod
Theropoda (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
s. Abelisaurids thrived during the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
period, on the ancient southern
supercontinent
In geology, a supercontinent is the assembly of most or all of Earth's continent, continental blocks or cratons to form a single large landmass. However, some geologists use a different definition, "a grouping of formerly dispersed continents", ...
of
Gondwana
Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
, and today their
fossil
A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...
remains are found on the modern
continent
A continent is any of several large geographical regions. Continents are generally identified by convention (norm), convention rather than any strict criteria. A continent could be a single large landmass, a part of a very large landmass, as ...
s of
Africa
Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...
and
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
, as well as on the
Indian subcontinent
The Indian subcontinent is a physiographic region of Asia below the Himalayas which projects into the Indian Ocean between the Bay of Bengal to the east and the Arabian Sea to the west. It is now divided between Bangladesh, India, and Pakista ...
and the island of
Madagascar
Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...
. Isolated teeth were found in the Late Jurassic of Portugal, and the Late Cretaceous genera ''
Tarascosaurus'', ''
Arcovenator'' and ''
Caletodraco'' have been described in
France
France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
.
Abelisaurids possibly first appeared during the
Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...
period based on fossil records, and some genera survived until the end of the
Mesozoic
The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...
era, around .
Like most theropods, abelisaurids were
carnivorous
A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose nutrition and energy requirements are met by consumption of animal tissues (mainly mu ...
biped
Bipedalism is a form of terrestrial locomotion where an animal moves by means of its two rear (or lower) limbs or legs. An animal or machine that usually moves in a bipedal manner is known as a biped , meaning 'two feet' (from Latin ''bis'' ' ...
s. They were characterized by stocky hind limbs and extensive ornamentation of the
skull
The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate.
In the human, the skull comprises two prominent ...
bones, with grooves and pits. In many abelisaurids, such as ''
Carnotaurus
''Carnotaurus'' (; ) is a genus of Theropoda, theropod dinosaur that lived in South America during the Late Cretaceous period, probably sometime between 72 and 69 million years ago. The only species is ''Carnotaurus sastrei''. Known from a si ...
'', the forelimbs are
vestigial
Vestigiality is the retention, during the process of evolution, of genetically determined structures or attributes that have lost some or all of the ancestral function in a given species. Assessment of the vestigiality must generally rely on co ...
, the skull is shorter, and bony crests grow above the eyes. Most of the known abelisaurids would have been between 5 and 9 m (17 to 30 ft) in length, from snout to tip of tail, with a new and as yet unnamed specimen from northwestern Turkana in Kenya, Africa reaching a possible length of 11–12 m (36 to 39 ft).
Before becoming well known, fragmentary abelisaurid remains were occasionally misidentified as possible South American
tyrannosaurid
Tyrannosauridae (or tyrannosaurids, meaning "tyrant lizards") is a family of coelurosaurian theropod dinosaurs that comprises two subfamilies containing up to fifteen genera, including the eponymous ''Tyrannosaurus''. The exact number of genera ...
s.
["Abelisaurus." In: Dodson, Peter & Britt, Brooks & Carpenter, Kenneth & Forster, Catherine A. & Gillette, David D. & Norell, Mark A. & Olshevsky, George & Parrish, J. Michael & Weishampel, David B. ''The Age of Dinosaurs''. Publications International, LTD. p. 105. .]
Description

Abelisaurid hind limbs were more typical of ceratosaurs, with the
astragalus
Astragalus may refer to:
* ''Astragalus'' (plant), a large genus of herbs and small shrubs
*Astragalus (bone)
The talus (; Latin for ankle or ankle bone; : tali), talus bone, astragalus (), or ankle bone is one of the group of foot bones known ...
and
calcaneum
In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel; : calcanei or calcanea) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is t ...
(upper ankle bones) fused to each other and to the
tibia
The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...
, forming a tibiotarsus. The tibia was shorter than the
femur
The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg.
The Femo ...
, giving the hind limb stocky proportions. Three functional digits were on the foot (the second, third, and fourth), while the first digit, or
hallux
Toes are the digits of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being ''digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being ''plantigrade''; ...
, did not contact the ground.
Skull

Although skull proportions varied, abelisaurid skulls were generally very tall and very short in length. In ''Carnotaurus'', for example, the skull was nearly as tall as it was long. The
premaxilla
The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammals h ...
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
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 ve ...
bones, projected into the eye socket
In anatomy, the orbit is the cavity or socket/hole 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. In the adult human, the volume of the orbit is ...
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 is seeing with two eyes. The Field_of_view, field of view that can be surveyed with two eyes is greater than with one eye. To the extent that the visual fields of the two eyes overlap, #Depth, binocular depth can be perceived. Th ...
. 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
In the human skull, the frontal bone or sincipital bone is an unpaired bone which consists of two portions.'' Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bo ...
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 displayed for species recognition or intimidation. In '' Arcovenator'', the dorsal margin of the postorbital (and probably also the lacrimal) is thickened dorsolaterally, forming a strong and rugose bony brow ridge rising above the level of the skull roof. Possibly, this rugose brow ridge supported a keratinous or scaly structure for displays.
Fore limbs and hands
Data for the abelisaurid fore limbs are known from ''Eoabelisaurus
''Eoabelisaurus'' () is a genus of abelisauroid theropod dinosaur from the Lower Jurassic Cañadón Asfalto Formation of the Cañadón Asfalto Basin in Argentina, South America. The generic name combines a Greek ἠώς, (''eos''), "dawn", with t ...
'' and the carnotaurines ''Aucasaurus'', ''Carnotaurus'', and ''Majungasaurus''. All had small fore limbs, which seem to have been vestigial. The bones of the forearm (radius
In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...
and ulna
The ulna or ulnar bone (: ulnae or ulnas) is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the Radius (bone), radius, the forearm's other long ...
) were extremely short, only 25% of the length of the upper arm (humerus
The humerus (; : humeri) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius (bone), radius and ulna, and consists of three sections. The humeral upper extrem ...
) in ''Carnotaurus'' and 33% in ''Aucasaurus''. The entire arm was held straight, and the elbow joint was immobile.[
As is typical for ceratosaurs, the abelisaurid ]hand
A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the Koala#Characteristics, koala (which has two thumb#O ...
had four basic digits, but any similarity ends there. No wrist
In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carpal ...
bones existed, with the four palm bones (metacarpal
In human anatomy, the metacarpal bones or metacarpus, also known as the "palm bones", are the appendicular bones that form the intermediate part of the hand between the phalanges (fingers) and the carpal bones ( wrist bones), which articulate ...
s) attaching directly to the forearm. No phalanges
The phalanges (: phalanx ) are digit (anatomy), digital bones in the hands and foot, feet of most vertebrates. In primates, the Thumb, thumbs and Hallux, big toes have two phalanges while the other Digit (anatomy), digits have three phalanges. ...
(finger bones) were 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. Manual claws were very small in ''Eoabelisaurus'', and totally absent in carnotaurines.[
More primitive relatives such as '' Noasaurus'' and ''Ceratosaurus'' had longer, mobile arms with fingers and claws.] Paleobiologist Alexander O. Vargas suggested a major reason for the evolution towards vestigial fore limbs in the group was because of a genetic defect; the loss of function in'' HOXA11'' and ''HOXD11'', two genes that regulate the fore limbs' development.
Distribution
Abelisaurids are typically regarded as a Cretaceous period group. The earliest possible abelisaurid taxon is '' Eoabelisaurus mefi'' from the Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...
period of Argentina, though other researchers either consider it as a ceratosaurid, an abelisauroid or its sister taxon outside abelisaurids. Indeterminate remains are also known from the Jurassic
The Jurassic ( ) is a Geological period, geologic period and System (stratigraphy), stratigraphic system that spanned from the end of the Triassic Period million years ago (Mya) to the beginning of the Cretaceous Period, approximately 143.1 Mya. ...
period of Madagascar and Tanzania
Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...
. Abelisaurid remains are mainly known in the southern continents, which once made up the supercontinent
In geology, a supercontinent is the assembly of most or all of Earth's continent, continental blocks or cratons to form a single large landmass. However, some geologists use a different definition, "a grouping of formerly dispersed continents", ...
of Gondwana
Gondwana ( ; ) was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia (continent), Australia, Zea ...
. When first described in 1985, only ''Carnotaurus'' and ''Abelisaurus'' were known, both from the Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...
of South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
. Abelisaurids were then located in Late Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
India
India, officially the Republic of India, is a country in South Asia. It is the List of countries and dependencies by area, seventh-largest country by area; the List of countries by population (United Nations), most populous country since ...
(''Indosuchus'' and ''Rajasaurus'') and Madagascar
Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...
(''Majungasaurus''), which were closely connected for much of the Cretaceous. It was thought that the absence of abelisaurids from continental Africa
Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...
indicated that the group evolved
Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, re ...
after the separation of Africa from Gondwana, around 100 million years ago
Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to (i.e. years), or approximately 31.6 teraseconds.
Usage
Myr is in common use in fields such as Earth science and cosmology. Myr is also used w ...
. 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. In 2014, the description of '' Arcovenator escotae'' from southern France
France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
provided the first indisputable evidence of the presence of Abelisaurids in Europe
Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
. ''Arcovenator'' presents strong similarities with the Madagascan ''Majungasaurus'' and Indian abelisaurids, but not with the South American forms. ''Arcovenator'', ''Majungasaurus'', and Indian forms are united in the new clade Majungasaurinae.
Classification
Paleontologist
Paleontology, also spelled as palaeontology or palæontology, is the scientific study of the life of the past, mainly but not exclusively through the study of fossils. Paleontologists use fossils as a means to classify organisms, measure geolo ...
s Jose Bonaparte 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'', and from the Greek
Greek may refer to:
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group
*Greek language, a branch of the Indo-European language family
**Proto-Greek language, the assumed last common ancestor of all kno ...
word (') meaning lizard. The very common suffix ''-idae'' is usually applied to zoological
Zoology ( , ) is the scientific study of animals. Its studies include the anatomy, structure, embryology, Biological classification, classification, Ethology, habits, and distribution of all animals, both living and extinction, extinct, and ...
family
Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...
names and is derived from the Greek suffix -ιδαι (''-'') meaning 'descendants'.[Bonaparte, J.F. & Novas, F.E. (1985). Abelisaurus comahuensis, n.g., n.sp., Carnosauria of the Late Cretaceous of Patagonia".''Ameghiniana''. 21: 259–265. n Spanish/ref>
Abelisauridae is a family in rank-based ]Linnaean taxonomy
Linnaean taxonomy can mean either of two related concepts:
# The particular form of biological classification (taxonomy) set up by Carl Linnaeus, as set forth in his ''Systema Naturae'' (1735) and subsequent works. In the taxonomy of Linnaeus th ...
, within the infraorder
Order () is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between Family_(biology), family and Class_(biology), class. In biological classification, the order is a taxonomic rank used in the classific ...
Ceratosauria and the superfamily Abelisauroidea
Ceratosaurs are members of the clade Ceratosauria, a group of dinosaurs defined as all theropods sharing a more recent common ancestor with ''Ceratosaurus'' than with birds. The oldest known ceratosaur, ''Saltriovenator'', dates to the earliest ...
, which also contains the family Noasauridae
Noasauridae is an extinct family of theropod dinosaurs belonging to the group Ceratosauria. They were closely related to the short-armed Abelisauridae, abelisaurids, although most noasaurids had much more traditional body types generally simila ...
. It has had several definitions in phylogenetic taxonomy. It was originally defined as a node-based taxon
In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...
including ''Abelisaurus'', ''Carnotaurus'', their common ancestor, and all of its descendants.[Novas, F.E. (1997). "Abelisauridae". In: Currie, P.J. & Padian, K.P. ''Encyclopedia of Dinosaurs''. San Diego: Academic Press. Pp. 1–2 .]
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 such as '' Rugops'' or '' Ilokelesia'', which are thought to be more basal than ''Abelisaurus'' and would be included by a stem-based definition.[Sereno, P.C. (2005)]
Abelisauridae
. TaxonSearch. 7 November 2005. Retrieved 19 September 2006. Within the 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 '' Aucasaurus''), making establishment of defining features of the skeleton for the family as a whole more difficult. However, most are known from at least some skull bones, so known shared features come mainly from the skull.[Tykoski, R.S. & Rowe, T. (2004). "Ceratosauria". In: Weishampel, D.B., Dodson, P., & Osmolska, H. (Eds.) ''The Dinosauria'' (2nd edition). Berkeley: University of California Press. Pp. 47–70 ] 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
Cladistics ( ; from Ancient Greek 'branch') is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is ...
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.
Phylogeny
Below is a cladogram generated by Tortosa ''et al.'' (2014) in the description of '' Arcovenator'' and creation of a new subfamily Majungasaurinae.
''Ilokelesia'' was originally described as a sister group to the Abelisauroidea.[Coria, R.A. & Salgado, L. "A basal Abelisauria Novas 1992 (Theropoda-
Ceratosauria) from the Cretaceous Period of Patagonia, Argentina". In: Perez-Moreno, B, Holtz, T.R., Sanz, J.L., & Moratalla, J. (Eds.). ''Aspects of Theropod Paleobiology''. ''Gaia'' 15:89–102. ot printed until 2000/ref> 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 the 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.
Some scientists include '' Xenotarsosaurus'' from Argentina and '' Compsosuchus'' from India as basal abelisaurids, while others consider them to be outside the Abelisauroidea.[Martínez, R.D. and Novas, F.E. (2006). "''Aniksosaurus darwini gen. et sp. nov''., a new coelurosaurian theropod from the early Late Cretaceous of central Patagonia, Argentina". ''Revista del Museo Argentino de Ciencias Naturales'', nuevo serie 8(2):243-259] The French '' Genusaurus'' and '' Tarascosaurus'' have also been called abelisaurids but both are fragmentary and may be more basal ceratosaurians, though Tortosa ''et al.'' (2014) considered both to be distinct abelisaurids. Subsequent phylogenetic analyses recover ''Xenotarsosaurus'' and ''Tarascosaurus'' as an abelisaurid, but ''Genusaurus'' as either a noasaurid or 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'' (except ''Abelisaurus''), grouped together as a subclade of carnotaurines, which they named the Brachyrostra. In the same year Matthew T. Carrano and Scott D. Sampson published new large phylogenetic analysis of ceratosaurian. With the description of ''Eoabelisaurus
''Eoabelisaurus'' () is a genus of abelisauroid theropod dinosaur from the Lower Jurassic Cañadón Asfalto Formation of the Cañadón Asfalto Basin in Argentina, South America. The generic name combines a Greek ἠώς, (''eos''), "dawn", with t ...
'', Diego Pol and Oliver W. M. Rauhut (2012) combined these analyses and added 10n new characters. The following cladogram
A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
follows their analysis.
In the 2021 description of '' Llukalkan'', the following consensus tree was recovered.
Paleobiology
Feeding
Fossil teeth found amid the bones of a titanosaur from the Allen Formation
The Allen Formation is a geological formation in Argentina whose strata date back to the Late Cretaceous (middle Campanian to early Maastrichtian.Salgado et al., 2007 Dinosaur remains are among the fossils that have been recovered from the forma ...
of Argentina suggest that abelisaurids preyed upon or at least scavenged titanosaurs.
Ontogeny and growth
Studies of the abelisaurid ''Majungasaurus'' indicate that it was a much slower-growing dinosaur than other theropods, taking nearly 20 years to reach adult size. However, other mature abelisaurid specimens indicate that they generally reached a faster rate of maturation. The holotype of '' Aucasaurus'' had a minimum age of 11 years, the holotype of '' Niebla'' had a minimum age of 9 years, and MMCh-PV 69 had a minimum age of 14 years.
See also
* Timeline of ceratosaur research
References
External links
Abelisauridae at The Theropod Database
{{Taxonbar, from=Q134184
*
Dinosaur families
Cretaceous dinosaurs