This is an accepted version of this page
| Majungasaurinae | |
|---|---|
 | |
| Majungasaurus crenatissimus mounted skeleton,Stony Brook University | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Abelisauridae |
| Subfamily: | †Majungasaurinae Tortosaet al., 2014 |
| Type species | |
| †Majungasaurus crenatissimus | |
| Subgroups | |
| Synonyms | |
MajungasauriniTortosa et al., 2014 vide Delcourt, 2018 | |
Majungasaurinae (afterMajungasaurus, itself named after the city ofMahajanga inMadagascar) is a subfamily of large carnivoroustheropods from the UpperCretaceous, found in Madagascar,India,Spain, andFrance. It is a subgroup within the theropod familyAbelisauridae, aGondwanan clade known for their thick and often horned skulls and vestigial arms. The two subfamilies of Abelisauridae areCarnotaurinae, best known from theSouth AmericanCarnotaurus, and Majungasaurinae, consisting of Madagascar’sMajungasaurus and its closest relatives. Their ancestors emerged in the MiddleJurassic, 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, fasterornithopods. 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.
The abelisaurids all possess distinct, vestigial, and immobile forelimbs, with highly reduced manualphalanges.[2]Carnotaurus andMajungasaurus are closely related but distinguish by several skeletal features.Carnotaurus has eleven dorsal vertebrae butMajungasaurus has thirteen.[3]Carnotaurus has shortdentary bones and an almost verticalramus, while that ofMajungasaurus curved backward and had notable caudal projections.[citation needed] Majungasaurines also have low, wideantorbital fenestrae, a wide triangular plate posterior to theparietal, two holes for a cerebral vein by thesagittal crest, and a wide groove on theoccipital condyle.[4] These differences are important because derived abelisaurids are classed as either majungasaurines or carnotaurines based on their synapomorphies.
The first majungasaurine to be uncovered wasMajungasaurus, discovered in Madagascar in 1896, however was named as a species ofMegalosaurus.[5]Indosaurus andIndosuchus were both discovered in India and described in 1933 byCharles Alfred Matley andFriedrich von Huene asallosaurids. The nameMajungasaurus was erected byRené Lavocat in 1955 for some teeth and a dentary which showed that the animal was distinct fromMegalosaurus. In 1996, a species,Majungatholus was erected for a supposedpachycephalosaurid from Madagascar, however this turned out to belong to a specimen ofMajungasaurus. in 1991 that paleontologistJose Bonaparte theorized that these and many other theropods belonged to the same family, the abelisaurids.[6] Tortosa et al., 2014 created a new subfamily of abelisaurids, the Majungasaurinae, which unified abelisaurids from Europe, Madagascar and India into a single clade.[4]
Source:[7]
The clade Majungasaurinae is relatively new, proposed in March 2014 by paleontologist Thierry Tortosa and colleagues in the description ofArcovenator. It is defined as all abelisaurids more closely related toMajungasaurus than toCarnotaurus. The cladogram below shows the result of the study's phylogenetic analysis.[8]
| Abelisauridae |
| ||||||||||||||||||||||||
The following cladogram is a consensus tree primarily based on a paper describing ontogeny inLimusaurus. Only the phylogeny for Abelisauridae is depicted here.[9]
In the 2021 description ofLlukalkan, bothRahiolisaurus andDahalokely were placed outside of Majungasaurinae as basalbrachyrostrans. It agreed with the existence of a clade comprisingMajungasaurus,Indosaurus andRajasaurus but also foundArcovenator andGenusaurus to form asister taxon relationship.[10]
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 presumablyAustralia andAntarctica as well.[11] 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.[12]
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.[13]Majungasaurus is known to have preyed upon medium-sizedsauropods such asRapetosaurus, and its teeth marks have been found on the ribs of otherMajungasaurus. 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.[14]
.jpg)
.jpg)
.png)
.png)
.jpg)
.jpg)
.png)
.jpg)
