Majungasaurinae (after ''Majungasaurus'', itself named after the city of
Mahajanga
Mahajanga (French: Majunga) is a city and an administrative district on the northwest coast of Madagascar. The city of Mahajanga (Mahajanga I) is the capital of the Boeny Region. The district (identical to the city) had a population of 220,629 i ...
in
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 ...
) is a subfamily of large carnivorous
theropods
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 ...
from the Upper
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 ...
, found in Madagascar,
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 ...
, and
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 ...
. It is a subgroup within the theropod family
Abelisauridae
Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are found ...
, a
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 ...
n clade known for their thick and often horned skulls and vestigial arms. The two subfamilies of Abelisauridae are
Carnotaurinae
Carnotaurinae is a subfamily of the theropod dinosaur family Abelisauridae. It includes the dinosaurs ''Aucasaurus'' (from Argentina), ''Carnotaurus'' (from Argentina). The group was first proposed by American paleontologist Paul Sereno in 1998 ...
, best known from the
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 ...
n ''
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 ...
'', and Majungasaurinae, consisting of Madagascar’s ''
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 its closest relatives. Their ancestors emerged in 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 ...
, and the clade lasted until the Upper Cretaceous.
The majungasaurines were mid-sized, bipedal predators, but relatively slow moving. Their stout legs were built for striding, not running. They had tall, deep heads with powerful jaws, but small forearms without carpals in the wrists. Because of their slow gait and small arms, they likely preyed upon the larger, slower sauropods rather than the smaller, faster
ornithopod
Ornithopoda () is a clade of ornithischian dinosaurs, called ornithopods (), that started out as small, bipedal running grazers and grew in size and numbers until they became one of the most successful groups of herbivores in the Cretaceous world ...
s. Their ancestors lived on a unified southern continent, Gondwana, in the Early Cretaceous, but as the land mass divided they became distinct from their South American cousins, and eventually from each other.
Anatomical identification
The abelisaurids all possess distinct, vestigial, and immobile forelimbs, with highly reduced manual
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.
...
. ''Carnotaurus'' and ''Majungasaurus'' are closely related but distinguish by several skeletal features. ''Carnotaurus'' has eleven dorsal vertebrae but ''Majungasaurus'' has thirteen. ''Carnotaurus'' has short
dentary
In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower tooth, teeth in place. The mandible sits beneath the maxilla. It is the only movabl ...
bones and an almost vertical
ramus Ramus can refer to:
* A branch (botany)
* A portion of a bone (from Latin ''ramus'', "branch"), as in the Ramus of the mandible or Superior pubic ramus
* A nerve ramus such as the Dorsal ramus of spinal nerve
* A taxonomic rank ("branch" in English ...
, while that of ''Majungasaurus'' curved backward and had notable caudal projections. Majungasaurines also have low, wide
antorbital fenestra
An antorbital fenestra (plural: fenestrae) is an opening in the skull that is in front of the eye sockets. This skull character is largely associated with archosauriforms, first appearing during the Triassic Period. Among extant archosaurs, birds ...
e, a wide triangular plate posterior to the
parietal, two holes for a cerebral vein by the
sagittal crest
A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are exceptiona ...
, and a wide groove on the
occipital condyle
The occipital condyles are undersurface protuberances of the occipital bone in vertebrates, which function in articulation with the superior facets of the atlas vertebra.
The condyles are oval or reniform (kidney-shaped) in shape, and their anteri ...
. These differences are important because derived abelisaurids are classed as either majungasaurines or carnotaurines based on their synapomorphies.
History of study
The first majungasaurine to be uncovered was ''
Indosaurus
''Indosaurus'' () is a genus of carnivorous theropod dinosaur that lived in what is now India, about 69 to 66 million years ago during the Maastrichtian division of the Late Cretaceous. The species I. matleyi weighed roughly 700 kg (1540&nbs ...
'', discovered in India in 1933 by
Charles Alfred Matley
Charles Alfred Matley (1866–1947) was a British paleontologist and geologist in India, the British West Indies and Wales.
Matley was educated at Birmingham University, and earned a doctorate in geology (D.Sc.) from the University of London in J ...
and
Friedrich von Huene
Friedrich von Huene, born Friedrich Richard von Hoinigen, (March 22, 1875 – April 4, 1969) was a German paleontologist who renamed more dinosaurs in the early 20th century than anyone else in Europe. He also made key contributions about v ...
, and ''Majungasaurus'', discovered in Madagascar in 1955 by
René Lavocat
René Lavocat (August 24, 1909-August 9, 2007) was a French paleontologist who described several genera of African dinosaurs including the sauropod ''Rebbachisaurus'', as well as several extinct mammals such as the family Kenyamyidae. The mammal ...
. Both species were misidentified at the time of their discoveries as they were known from only partial remains: ''Indosaurus'' was believed to be an
allosaurid
Allosauridae is a family of medium to large bipedal, carnivorous allosauroid theropod dinosaurs from the Late Jurassic. Allosauridae is a fairly old taxonomic group, having been first named by the American paleontologist Othniel Charles Marsh in ...
, and ''Majungasaurus'' was believed to be a
pachycephalosaurid
Pachycephalosauria (; from Greek παχυκεφαλόσαυρος for 'thick headed lizards') is a clade of ornithischian dinosaurs. Along with Ceratopsia, it makes up the clade Marginocephalia. With the exception of two species, most pachycephal ...
. It was not until 1991 that paleontologist
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 ...
theorized that these and many other theropods belonged to the same family, the abelisaurids.
Classification
Taxonomy
* Family
Abelisauridae
Abelisauridae (meaning "Abel's lizards") is a family (or clade) of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are found ...
** Subfamily Majungasaurinae
*** ''
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 ...
''
*** ''
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 ...
''
*** ''
Indosaurus
''Indosaurus'' () is a genus of carnivorous theropod dinosaur that lived in what is now India, about 69 to 66 million years ago during the Maastrichtian division of the Late Cretaceous. The species I. matleyi weighed roughly 700 kg (1540&nbs ...
''
*** ''
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 ...
''
*** ''
Rahiolisaurus''
*** ''
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 the ...
''
Phylogeny
The clade Majungasaurinae is relatively new, proposed in March 2014 by paleontologist Thierry Tortosa. It is defined as all abelisaurids more closely related to ''Majungasaurus'' than to ''Carnotaurus''.
Paleobiology
Geographic range
The majungasaurines and their carnotaurine sister group emerged in what is now South America. From there they spread to the rest of Gondwana: modern Africa and India, and presumably
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
and
Antarctica
Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest contine ...
as well. Fragmentary evidence of abelisaurs in southern France indicates they may have spread into Europe as well, but the relationship of these species to the rest of Majungasaurinae is not well established.
Feeding habits
Like all abelisaurs, the majungasaurines were carnivorous and had bulbous teeth, short heads, and strong necks. This meant that their wide jaws were very powerful, and could crush their prey’s trachea or vertebrae once they bit down. ''Majungasaurus'' is known to have preyed upon medium-sized
sauropods
Sauropoda (), whose members are known as sauropods (; from '' sauro-'' + '' -pod'', 'lizard-footed'), is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads (relative to the rest of their bo ...
such as ''
Rapetosaurus
''Rapetosaurus'' ( ) is a genus of titanosaurian sauropod dinosaur that lived in Madagascar from 70 to 66 million years ago, at the end of the Cretaceous Period. Only one species, ''Rapetosaurus krausei'', has been identified.
Like other sauropod ...
'', and its teeth marks have been found on the ribs of other ''Majungasaurus''. Whether it actively hunted members of its own species or merely cannibalized their scavenged remains is unknown. This behavior has not been observed in any other majungasaurines.
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
{{Taxonbar, from=Q15304835
Abelisaurids