| Abelisaurus | |
|---|---|
 | |
| Reconstruction of theAbelisaurus skull with original bones of the holotype. Scale = 10 cm | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | Theropoda |
| Family: | †Abelisauridae |
| Clade: | †Furileusauria |
| Tribe: | †Carnotaurini |
| Genus: | †Abelisaurus Bonaparte &Novas, 1985 |
| Type species | |
| †Abelisaurus comahuensis Bonaparte & Novas, 1985 | |
| Synonyms | |
| |
Abelisaurus (/əˌbɛlɪˈsɔːrəs/; "Abel's lizard") is agenus of predatoryabelisauridtheropoddinosaur which lived during the LateCretaceousPeriod (Campanian) of what is nowSouth America. It was abipedalcarnivore that probably reached about 7.4 metres (24 ft 3 in) in length, although this is uncertain as it is known from only one partialskull.
Coining thetype speciesAbelisaurus comahuensis, both genus and species were named and described byArgentinepaleontologistsJosé Bonaparte andFernando Emilio Novas in 1985. The generic name recognizes Roberto Abel as the discoverer of thetype specimen, and also as the former director of the provincial Museum ofCipolletti inArgentina, where the specimen is housed. It also incorporates theGreekσαυρος (sauros), meaning 'lizard'. Thespecific namecomahuensis honors theComahue region of Argentina, where the fossil was found.[2]
Theholotype, MC 11098, was in 1983 uncovered at the "Cantera de la Pala Mécanica"-site in the Lago Pellegrini quarries exploited by Abel since 1975. This single knownfossil ofAbelisaurus consists of a skull, lacking the lower jaws, that is incomplete, especially on the right side. Most of the connections between the snout and the back of the skull are absent. It is also missing most of thepalate (roof of the mouth). Despite the missing pieces, it could be estimated at over 85 centimetres (33 in) long.[2]
Abelisaurus is one of the many dinosaurs that have been discovered inPatagonia. It was originally described as coming from theAllen Formation but subsequent research proved the remains were actually found in the olderAnacleto Formation (part of theNeuquén Group) ofRío Negro Province, Argentina. However, locallyAbelisaurus is known to have come from the Sr. Fernandez field, which is in theCampanianAllen Formation, which makes its stratigraphic position unclear.[3] The Anacleto is ageologic formation in South America, dating from the earlyCampanian stage of theLate Cretaceous Period, between 83 and 80million years ago.[4]
In 2009, Novas suggested thatAucasaurus garridoi might be ajunior synonym ofAbelisaurus comahuensis.[5] In 2010,Gregory S. Paul renamedAucasaurus garridoi intoAbelisaurus garridoi.[6] This has found no acceptance.[citation needed]
As only the skull is known, it has proven difficult to provide a reliable size estimate ofAbelisaurus. It has transpired that abelisaurids have relatively short heads. In 2010,Gregory S. Paul estimated its body length at ten metres (32 ft 10 in), its weight at 3 tonnes (3 long tons; 3 short tons).[6] In 2012Thomas Holtz gave a possible length of 11 metres (36.3 feet).[7] In 2016, its length was estimated to be 7.4 metres (24 ft 3 in) in a comprehensive analysis of abelisaur size.[8] Others authors gave a similar size at 7.2 metres (23.6 feet) and 1.65 tonnes (1.82 short tons).[9]
Skull length was estimated at 85 centimetres (33+1⁄2 in) in 1985. The skull is relatively deep. Although there are no bony crests or horns, like those found in some other abelisaurids, such asCarnotaurus, rough ridges on the snout and above the eyes might have supported some kind of crest made out ofkeratin, which would not have become fossilized. The skull roof is thickened. There are also very largefenestrae (window-like openings) in the skull, which are found in many dinosaurs and reduce skull weight. One of these is a large triangularantorbital fenestra in the side of the snout. The eye socket behind it is rather high. It is constricted in the middle by bony projections of thelacrimal bone in the front and thepostorbital bone at the rear. The eye was located above the constriction. Behind the eye socket a large triangularinfratemporal fenestra is present. Its form reflects a strong forward inclination of the back of the skull.[2]
The front snout bone, thepremaxilla, bore four relatively small teeth. Themaxilla behind it had at least seven, but perhaps as many as thirteen, larger teeth.[2]
Bonaparte and Novas placedAbelisaurus in the newly createdfamilyAbelisauridae in 1985. They thought it was a member of theCarnosauria.[2]Abelisaurus was the first abelisaurid named.[5]
Many other abelisaurids have since been discovered, including much more complete specimens ofAucasaurus,Carnotaurus andMajungasaurus. They showed that abelisaurids were not carnosaurs in the modern sense, but belonged to theNeoceratosauria instead. Some scientists placeAbelisaurus as abasal abelisaurid, outside the subfamilyCarnotaurinae.[10][11] Others are less certain of its position.[12][13]Abelisaurus shares some skull features, such as a relative elongation, with thecarcharodontosaurids, a group unrelated to other species assigned to the Abelisauridae, and, since it is known only from a skull, it has been suggested that future discoveries may show thatAbelisaurus was in fact a carcharodontosaurid.[14] However, this is thought unlikely.[13]
In their description of theabelisauridLlukalkan, Federico Gianechini and colleagues performed a phylogenetic analysis to test the affinities of the new taxon. The simplified strict consensus tree of the analysis is shown below.[15]
As the skull ofAbelisaurus was relatively broad at the back, Bonaparte and Novas drew a comparison between the newly described species and the also wide-skulledTyrannosauridae. They assumed that, just as tyrannosaurids,Abelisaurus were theapex predators of theirecosystem.[2]
In 2010, Paul proposed thatAbelisaurus huntedtitanosauriansauropods, such asAntarctosaurus,Pellegrinisaurus,Barrosasaurus andNeuquensaurus.[6]
.png)
.png)
.jpg)
.jpg)
.png)
.jpg)
