Abelisauridae (meaning "Abel's lizards") is a
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
(or
clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
) 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 earliest ...
n
theropod
Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...
dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...
s. Abelisaurids thrived during the
Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
period
Period may refer to:
Common uses
* Era, a length or span of time
* Full stop (or period), a punctuation mark
Arts, entertainment, and media
* Period (music), a concept in musical composition
* Periodic sentence (or rhetorical period), a concept ...
, 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, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...
, 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 preserved ...
remains are found on the modern
continent
A continent is any of several large landmasses. Generally identified by convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. Ordered from largest in area to smallest, these seven ...
s of
Africa
Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
and
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...
, as well as on the
India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
n
subcontinent
A continent is any of several large landmasses. Generally identified by convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. Ordered from largest in area to smallest, these seven ...
and the island of
Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
. Isolated teeth were found in the Late Jurassic of Portugal, and the Late Cretaceous genera ''
Tarascosaurus'' and ''
Arcovenator
''Arcovenator'' ("Arc hunter") is an extinct genus of abelisaurid theropod dinosaurs hailing from the Late Cretaceous of France. The type and only described species is ''Arcovenator escotae''.
Description
Though shallower, the nearly complet ...
'' have been described in
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
.
Abelisaurids first appear in the fossil record of the early middle
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 Mya. The J ...
period, and at least two genera (the Moroccan ''
Chenanisaurus
''Chenanisaurus'' is a genus of predatory abelisaurid dinosaur, with a single known species ''C. barbaricus''. It comes from the upper Maastrichtian phosphates of the Ouled Abdoun Basin in Morocco, North Africa. The animal is known from a holo ...
'' and the Madagascan ''
Majungasaurus
''Majungasaurus'' (; ) is a genus of abelisaurid theropod dinosaur that lived in Madagascar from 70 to 66 million years ago, at the end of the Cretaceous Period (geology), Period, making it one of the last known non-avian dinosaurs that went ex ...
'') survived until the end of the
Mesozoic
The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...
era 66 million years ago.
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 food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...
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' (from Latin ''bis'' 'double' a ...
s. They were characterized by stocky hind limbs and extensive ornamentation of the
skull
The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...
bones, with grooves and pits. In many abelisaurids, such as ''
Carnotaurus
''Carnotaurus'' (; ) is a genus of theropod dinosaur that lived in South America during the Late Cretaceous period, probably sometime between 71 and 69 million years ago. The only species is ''Carnotaurus sastrei''. Known from a single well-p ...
'', 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 thirteen 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
![Abelisauridae_Scale](https://upload.wikimedia.org/wikipedia/commons/2/22/Abelisauridae_Scale.svg)
Abelisaurid hind limbs were more typical of ceratosaurs, with the
astragalus
''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to tempe ...
and
calcaneum
In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is the point of the hock.
...
(upper ankle bones) fused to each other and to the
tibia
The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...
, forming a tibiotarsus. The tibia was shorter than the
femur
The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with ...
, 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 (fingers) 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 '' pl ...
, did not contact the ground.
Skull
![Abelisaurus comahuensis](https://upload.wikimedia.org/wikipedia/commons/e/e9/Abelisaurus_comahuensis.JPG)
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 mammal has b ...
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 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 , of ...
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
In biology, binocular vision is a type of vision in which an animal has two eyes capable of facing the same direction to perceive a single three-dimensional image of its surroundings. Binocular vision does not typically refer to vision where an ...
. 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
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 ...
, the frontal bone
The frontal bone is a bone in the human skull. The bone consists of two portions.''Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bony part of the forehead, par ...
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'' (; ) is a genus of abelisaurid theropod dinosaur that lived in Madagascar from 70 to 66 million years ago, at the end of the Cretaceous Period (geology), Period, making it one of the last known non-avian dinosaurs that went ex ...
'' and ''Rajasaurus
''Rajasaurus'' (meaning "princely lizard") is a genus of carnivorous abelisaurid theropod dinosaur from the Late Cretaceous of India, containing one species: ''Rajasaurus narmadensis''. The bones were excavated from the Lameta Formation in th ...
'' 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 may refer to:
Technology
* Display device, output device for presenting information, including:
** Cathode ray tube, video display that provides a quality picture, but can be very heavy and deep
** Electronic visual display, output devi ...
ed for species recognition or intimidation. In ''Arcovenator
''Arcovenator'' ("Arc hunter") is an extinct genus of abelisaurid theropod dinosaurs hailing from the Late Cretaceous of France. The type and only described species is ''Arcovenator escotae''.
Description
Though shallower, the nearly complet ...
'', 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 abelisaurid 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) of a circle or sphere is any of the line segments from its center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', meaning ray but also the ...
and ulna
The ulna (''pl''. ulnae or ulnas) is a long bone found in the forearm that stretches from the elbow to the smallest finger, and when in anatomical position, is found on the medial side of the forearm. That is, the ulna is on the same side of t ...
) were extremely short, only 25% of the length of the upper arm (humerus
The humerus (; ) 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 and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...
) 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 (which has two opposable thumbs on each "h ...
had four basic digits, but any similarity ends there. No wrist
In human anatomy, the wrist is variously defined as (1) the Carpal bones, 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 ...
bones existed, with the four palm bones (metacarpal
In human anatomy, the metacarpal bones or metacarpus form the intermediate part of the skeletal hand located between the phalanges of the fingers and the carpal bones of the wrist, which forms the connection to the forearm. The metacarpal bones ...
s) attaching directly to the forearm. No phalanges
The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones.
...
(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
''Noasaurus'' ("Northwestern Argentina lizard") is a genus of ceratosaurian theropod dinosaur genus from the late Campanian-Maastrichtian (Late Cretaceous) of Argentina. The type and only species is ''N. leali''.
Discovery and naming
In the m ...
'' 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
Abelisauroids are typically regarded as a Cretaceous group, though the earliest abelisaurid remains are known from the Middle 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 Mya. The J ...
of Argentina (classified as the species '' Eoabelisaurus mefi'') and possibly Madagascar (fragmentary remains of an unnamed species); possible abelisaurid remains (an isolated left tibia, right femur and right tibia) were also discovered in Late Jurassic Tendaguru Beds in Tanzania
Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands and ...
. 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, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...
. 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 younger 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 ''creta'', the ...
of South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...
. Abelisaurids were then located in Late Cretaceous
The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of th ...
India
India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
(''Indosuchus'' and ''Rajasaurus'') and Madagascar
Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...
(''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 in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...
indicated that the group evolved
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation ...
after the separation of Africa from Gondwana, around 100 million years ago
The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds.
Usage
Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (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. In 2014, the description of '' Arcovenator escotae'' from southern France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
provided the first indisputable evidence of the presence of Abelisaurids in Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
. ''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
Majungasaurinae (after ''Majungasaurus'', itself named after the city of Mahajanga in Madagascar) is a subfamily of large carnivorous theropods from the Upper Cretaceous, found in Madagascar, India, and France. It is a subgroup within the thero ...
.
Classification
Paleontologist
Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...
s Jose Bonaparte
Jose is the English transliteration of the Hebrew and Aramaic name ''Yose'', which is etymologically linked to ''Yosef'' or Joseph. The name was popular during the Mishnaic and Talmudic periods.
* Jose ben Abin
* Jose ben Akabya
*Jose the Galile ...
and Fernando Novas Fernando Emilio Novas (born 1960) is an Argentine paleontologist working for the Comparative Anatomy Department of the Bernardino Rivadavia Natural Sciences Museum in Buenos Aires, Argentina. 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:
Greece
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 ...
word (') meaning lizard. The very common suffix ''-idae'' is usually applied to zoological
Zoology ()The pronunciation of zoology as is usually regarded as nonstandard, though it is not uncommon. is the branch of biology that studies the animal kingdom, including the structure, embryology, evolution, classification, habits, and dis ...
family
Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...
names and is derived from the Greek suffix -ιδαι (''-''), which indicates a plural noun.[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
N, or n, is the fourteenth Letter (alphabet), letter in the Latin alphabet, used in the English alphabet, modern English alphabet, the alphabets of other western European languages and others worldwide. Its name in English is English alphabet# ...
/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 t ...
, within the infraorder
Order ( la, ordo) is one of the eight major hierarchical taxonomic ranks in Linnaean taxonomy. It is classified between family and class. In biological classification, the order is a taxonomic rank used in the classification of organisms and ...
Ceratosauria and the superfamily Abelisauroidea
Abelisauroidea is typically regarded as a Cretaceous group, though the earliest abelisauridae remains are known from the Middle Jurassic of Argentina (classified as the species Eoabelisaurus mefi) and possibly Madagascar (fragmentary remains of ...
, 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 abelisaurids, although most noasaurids had much more traditional body types generally similar to other th ...
. It has had several definitions in phylogenetic taxonomy
Phylogenetic nomenclature is a method of nomenclature for taxa in biology that uses phylogenetic definitions for taxon names as explained below. This contrasts with the traditional approach, in which taxon names are defined by a '' type'', which ...
. It was originally defined as a node-based taxon
In biology, a taxon (back-formation from ''taxonomy''; plural 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 nam ...
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
''Rugops'' (meaning ‘wrinkle face’) is a monospecific genus of basal abelisaurid theropod dinosaur from Niger that lived during the Late Cretaceous period (Cenomanian stage, ~95 Ma) in what is now the Echkar Formation. The type and only spec ...
'' 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
''Aucasaurus'' is a genus of medium-sized abelisaurid theropod dinosaur from Argentina that lived during the Late Cretaceous (Santonian to Campanian stage) of the Anacleto Formation. It was smaller than the related ''Carnotaurus'', although more ...
''), 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 carcharodontosaurid
Carcharodontosauridae (carcharodontosaurids; from the Greek καρχαροδοντόσαυρος, ''carcharodontósauros'': "shark-toothed lizards") is a group of carnivorous theropod dinosaurs. In 1931, Ernst Stromer named Carcharodontosauridae ...
s. 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 (; ) 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 typically shared derived char ...
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
''Arcovenator'' ("Arc hunter") is an extinct genus of abelisaurid theropod dinosaurs hailing from the Late Cretaceous of France. The type and only described species is ''Arcovenator escotae''.
Description
Though shallower, the nearly complet ...
'' 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
''Xenotarsosaurus'' is a genus of abelisaurid theropod dinosaur that lived during the Late Cretaceous of Argentina.
Discovery
In 1980 geologist Juan Carlos Sciutto discovered a rich fossil site six kilometres north of the Ocho Hermanos ranch in ...
'' from Argentina and ''Compsosuchus
''Compsosuchus'' (meaning "elegant crocodile") is an extinct genus of abelisauroid dinosaur. It lived during the Late Cretaceous in India.
Discovery and naming
''Compsosuchus'' was described in 1933 by von Huene and Matley. The type species ...
'' 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
''Genusaurus'' ( ; meaning "knee lizard") is a genus of abelisauroid dinosaur from the Early Cretaceous. Its fossils were found in France. ''Genusaurus'' is believed to have lived during the Albian stage, around 112-100 million years ago.
D ...
'' and '' Tarascosaurus'' have also been called abelisaurids but both are fragmentary and may be more basal ceratosaurians.
With the description of ''Skorpiovenator
''Skorpiovenator'' ("scorpion hunter") is a genus of abelisaurid theropod dinosaur from the Late Cretaceous (Cenomanian to Turonian) Huincul Formation of Argentina. It is one of the most complete and informative abelisaurids yet known, describe ...
'' 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 abelisaurid 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 ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...
follows their analysis.
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 formati ...
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. Similar studies on other abelisaurid genera indicate that this slow maturation may have been a common trait to the whole of the Abelisauridae.
See also
* Timeline of ceratosaur research
This timeline of ceratosaur research is a chronological listing of events in the history of paleontology focused on the ceratosaurs, a group of relatively primitive, often horned, predatory theropod dinosaurs that became the apex predators of ...
References
External links
Abelisauridae at The Theropod Database
{{Taxonbar, from=Q134184
*
Prehistoric dinosaur families