Majungasaurus
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{{Taxobox
| name = ''Majungasaurus''
| fossil_range = [[Late Cretaceous]]
| image = Majungasaurus head BW.jpg
| image width = 200 pixels
| regnum = [[Animal]]ia
| phylum = [[Chordate|Chordata]]
| classis = [[Reptile|Sauropsida]]
| superordo = [[Dinosauria]]
| ordo = [[Saurischia]]
| subordo = [[Theropod]]a
| infraordo = [[Ceratosauria]]
| familia = [[Abelisaur]]idae
| genus = '''''Majungasaurus'''''
| genus_authority = [[René Lavocat|Lavocat]], 1955
| subdivision_ranks = [[Species]]
| subdivision = *'''''M. crenatissimus''''' ([[Type (zoology)|type]]) <br/><small>([[Charles Depéret|Depéret]], 1896) </small>
| synonyms =
''Majungatholus''<br/> <small>Sues and Taquet, 1979</small>
}}
'''''Majungasaurus''''' ({{pronEng|məˌdʒuːŋgəˈsɔrəs}} or mah-JOON-gah-''SAWR''-us; meaning "Mahajanga lizard") is a [[genus]] of [[abelisaurid]] [[theropod]] [[dinosaur]] that lived in [[Madagascar]] from 70 to 65 [[million years ago]], at the end of the [[Cretaceous]] [[Period (geology)|Period]]. Only one [[species]] (''M. crenatissimus'') has been identified. This dinosaur was briefly called ''Majungatholus'', a name which is now considered a [[junior synonym]] of ''Majungasaurus''.
Like other abelisaurids, ''Majungasaurus'' was a [[biped]]al [[predator]] with a short snout. Although the forelimbs are not completely known, they were very short, while the hindlimbs were longer and very stocky. It can be distinguished from other abelisaurids by its wider skull, the very rough texture and thickened bone on the top of its snout, and the single rounded horn on the roof of its [[skull]], which was originally mistaken for the dome of a [[pachycephalosaur]]. It also had more [[teeth]] in both upper and lower jaws than most abelisaurids.
Known from several well-preserved skulls and abundant skeletal material, ''Majungasaurus'' has recently become one of the best-studied theropod dinosaurs from the [[Southern Hemisphere]]. It appears to be most closely related to abelisaurids from [[India]] rather than [[South America]] or [[continent]]al [[Africa]], a fact which has important [[biogeography|biogeographical]] implications. ''Majungasaurus'' was the [[apex predator]] in its [[ecosystem]], mainly preying on [[sauropod]]s like ''[[Rapetosaurus]]'', and is also the only dinosaur for which direct evidence of [[Cannibalism (zoology)|cannibalism]] is known.
==Description==
''Majungasaurus'' was a medium-sized theropod that typically measured 6–7 [[meter]]s (20–23 [[foot (unit of length)|ft]]) in length, including its tail.<ref name=krauseetal2007>{{cite_book |last=Krause |first=David W. |coauthors=Sampson, Scott D.; Carrano, Matthew T.; & O'Connor, Patrick M. |year=2007 |chapter=Overview of the history of discovery, taxonomy, phylogeny, and biogeography of ''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar |editor=Sampson, Scott D.; & Krause, David W. (eds.) |title=''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar |series=Society of Vertebrate Paleontology Memoir '''8''' |pages=1–20 |url=http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1671%2F0272-4634%282007%2927%5B1%3AOOTHOD%5D2.0.CO%3B2}}</ref> Fragmentary remains of larger individuals indicate that some adults reached lengths of more than 8 meters (26 ft).<ref name=sampsonwitmer2007>{{cite_book |last=Sampson |first=Scott D. |coauthors=& Witmer, Lawrence M. |year=2007 |chapter=Cranofacial anatomy of ''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar|editor=Sampson, Scott D.; & Krause, David W. (eds.) |title=''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar |series=Society of Vertebrate Paleontology Memoir '''8''' |pages=32–102 |url=http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1671%2F0272-4634%282007%2927%5B32%3ACAOMCT%5D2.0.CO%3B2}}</ref> Scientists estimate that an average adult ''Majungasaurus'' weighed more than 1100 [[kilogram]]s (2400 [[Pound (mass)|lb]]), although the largest animals would have weighed more.<ref name=sampsonwitmer2007/> Its 8–9 meter (26–30 ft) relative ''[[Carnotaurus]]'' has been estimated to weigh 1500 kilograms (3300 lb).<ref name=mazettaetal1998>{{cite_journal |last=Mazzetta |first=Gerardo V. |coauthors=Fariña, Richard A.; & Vizcaíno, Sergio F. |year=1998 |title=On the paleobiology of the South American horned theropod ''Carnotaurus sastrei'' Bonaparte |journal=Gaia |volume=15 |pages=185–192 |url=http://www.mnhn.ul.pt/geologia/publicageo.htm}}</ref>
[[Image:Majungasaurus scale1.png|thumb|left|230px|''Majungasaurus crenatissimus'' compared in size to a human]]
The skull of ''Majungasaurus'' is exceptionally well-known compared to most theropods and generally similar to that of other abelisaurids. Like other abelisaurid skulls, its length was proportionally short for its height, although not as short as in ''Carnotaurus''. The skulls of large individuals measured 60–70 [[centimeter]]s (24–28 [[inch|in]]) long. The tall [[premaxilla]] (frontmost upper jaw bone), which made the tip of the snout very blunt, was also typical of the family. However, the skull of ''Majungasaurus'' was markedly wider than in other abelisaurids. All abelisaurids had a rough, sculptured texture on the outside faces of the skull bones, and ''Majungasaurus'' was no exception. This was carried to an extreme on the [[nasal bone]]s of ''Majungasaurus'', which were extremely thick and fused together, with a low central ridge running along the half of the bone closest to the nostrils. A distinctive dome-like horn protruded from the fused [[frontal bone]]s on top of the skull as well. In life, these structures would have been covered with some sort of [[integument]], possibly made of [[keratin]]. [[Computed tomography]] (CT scanning) of the skull shows that both the nasal structure and the frontal horn contained hollow [[Sinus (anatomy)|sinus]] cavities, perhaps to reduce weight.<ref name=sampsonwitmer2007/> The teeth were typical of abelisaurids in having short [[Crown (tooth)|crowns]], although ''Majungasaurus'' bore 17 teeth in both the [[maxilla]] of the upper jaw and the [[dentary]] of the lower jaw, more than in any other abelisaurid except ''[[Rugops]]''.<ref name=smith2007>{{cite_book |last=Smith |first=Joshua B. |year=2007 |chapter=Dental morphology and variation in ''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar |editor=Sampson, Scott D.; & Krause, David W. (eds.) |title=''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar |series=Society of Vertebrate Paleontology Memoir '''8''' |pages=103–126 |url=http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1671%2F0272-4634%282007%2927%5B103%3ADMAVIM%5D2.0.CO%3B2}}</ref>
[[Image:Majungasaurus BW.jpg|thumb|right|300px|''Majungasaurus crenatissimus'']]
The [[postcrania]]l skeleton of ''Majungasaurus'' closely resembles those of ''Carnotaurus'' and ''[[Aucasaurus]]'', the only other abelisaurid genera for which complete skeletal material is known. ''Majungasaurus'' was bipedal, with a long tail to balance out the head and torso, putting the [[center of gravity]] over the hips. Although the cervical ([[neck]]) [[vertebra]]e had numerous cavities and excavations (pleurocoels) to reduce their weight, they were robust, with exaggerated [[muscle]] attachment sites and [[rib]]s that interlocked for strength. [[Ossification|Ossified]] [[tendon]]s attached to the cervical ribs, giving them a forked appearance, as seen in ''Carnotaurus''. All of these features resulted in a very strong and muscular neck. Uniquely, the cervical ribs of ''Majungasaurus'' had long depressions along the sides for weight reduction.<ref name=oconnor2007>{{cite_book |last=O'Connor |first=Patrick M. |year=2007 |chapter=The postcranial axial skeleton of ''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar |editor=Sampson, Scott D.; & Krause, David W. (eds.) |title=''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar |series=Society of Vertebrate Paleontology Memoir '''8''' |pages=127–162 |url=http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1671%2F0272-4634%282007%2927%5B127%3ATPASOM%5D2.0.CO%3B2}}</ref> The [[humerus]] (upper arm bone) is the only bone of the forelimb yet described, but it was short and curved, closely resembling those of ''Aucasaurus'' and ''Carnotaurus''. This may indicate that ''Majungasaurus'' had similar very short forelimbs with four digits. Like other abelisaurids, the hindlimbs were stocky and short compared to body length. The [[tibia]] (lower leg bone) of ''Majungasaurus'' was even stockier than that of its relative ''Carnotaurus'', with a prominent crest on the knee. The [[talus bone|astragalus]] and [[calcaneum]] (ankle bones) were fused together, and the feet bore three functional digits, with a smaller first digit that did not contact the ground.<ref name=carrano2007>{{cite_book |last=Carrano |first=Matthew T. |year=2007 |chapter=The appendicular skeleton of ''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar |editor=Sampson, Scott D.; & Krause, David W. (eds.) |title=''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar |series=Society of Vertebrate Paleontology Memoir '''8''' |pages=163–179 |url=http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1671%2F0272-4634%282007%2927%5B163%3ATASOMC%5D2.0.CO%3B2}}</ref>
==Classification and systematics==
''Majungasaurus'' is classified as a member of the theropod [[clade]] Abelisauridae, which is considered a [[family (biology)|family]] in [[Linnaean taxonomy]]. Along with the family [[Noasauridae]], abelisaurids are included in the superfamily [[Abelisauroidea]], which is in turn a subdivision of the [[infraorder]] [[Ceratosauria]].<ref name=krauseetal2007/><ref name=serenoetal2004>{{cite_journal |last=Sereno |first=Paul C. |authorlink=Paul Sereno |year=2007 |title=New dinosaurs link southern landmasses in the Mid-Cretaceous |journal=Proceedings of the Royal Society of London B: Biological Sciences |volume=271 |issue=1546 |pages=1325–1330 |doi=10.1098/rspb.2004.2692}}</ref> Abelisaurids are known for their tall skulls with blunt snouts, extensive sculpturing on the outer surfaces of the facial bones ([[convergent evolution|convergent]] with [[carcharodontosaurid]]s), very reduced ([[atrophy|atrophied]]) forelimbs (convergent with [[tyrannosaurid]]s), and stocky hindlimb proportions, among other features.<ref name=tykoskirowe2004>{{cite_book |last=Tykoski |first=Ronald B. |coauthors=& Rowe, Timothy. |year=2004 |chapter=Ceratosauria |editor=[[David Weishampel|Weishampel, David B.]]; [[Peter Dodson|Dodson, Peter]]; & Osmólska, Halszka (eds.) |title=The Dinosauria |edition=Second Edition |publisher=University of California Press |location=Berkeley |pages=47–70 |isbn=0-520-24209-2}}</ref>
As with many dinosaur families, the [[systematics]] ([[evolution]]ary relationships) within the family Abelisauridae are confused. Several [[cladistic]] studies have indicated that ''Majungasaurus'' shares a close relationship with ''Carnotaurus'' from South America,<ref name=serenoetal2004/><ref name=tykoskirowe2004/> while others were unable to firmly place it in the [[phylogeny]].<ref name=coriaetal2002>{{cite_journal |last=Coria |first=Rodolfo A. |authorlink=Rodolfo Coria |coauthors=Chiappe, Luis M.; & Dingus, Lowell. |year=2002 |title=A new close relative of ''Carnotaurus sastrei'' Bonaparte 1985 (Theropoda: Abelisauridae) from the Late Cretaceous of Patagonia |journal=Journal of Vertebrate Paleontology |volume=22 |issue=2 |pages=460–465 |url=http://www.bioone.org/perlserv/?request=get-document&doi=10.1671%2F0272-4634%282002%29022%5B0460%3AANCROC%5D2.0.CO%3B2 |doi=10.1671/0272-4634(2002)022[0460:ANCROC]2.0.CO;2 |format=subscription required |doilabel=10.1671/0272-4634(2002)022[0460:ANCROC]2.0.CO;2}}</ref> The most recent analysis, using the most complete information, instead recovered ''Majungasaurus'' in a clade with ''[[Rajasaurus]]'' and ''[[Indosaurus]]'' from India, but excluding South American genera like ''Carnotaurus'', ''[[Ilokelesia]]'', ''[[Ekrixinatosaurus]]'', ''Aucasaurus'' and ''[[Abelisaurus]]'', as well as ''Rugops'' from mainland Africa. This leaves open the possibility of separate clades of abelisaurids in western and eastern [[Gondwana]].<ref name=krauseetal2007/> Detailed description of known abelisaurids like ''Aucasaurus'' as well as future discoveries and analyses may help to resolve the phylogenetic picture.
==Discovery and naming==
[[France|French]] [[paleontologist]] [[Charles Depéret]] described the first theropod remains from northwestern Madagascar in 1896. These included two teeth, a claw, and some vertebrae discovered along the [[Betsiboka River]] by a French army officer and deposited in the collection of what is now the [[Université Claude Bernard Lyon 1]]. Depéret referred these fossils to the genus ''[[Megalosaurus]]'', which at the time was a [[wastebasket taxon]] containing any number of unrelated large theropods, as the new species ''M. crenatissimus''.<ref name=deperet1896>{{cite_journal |last=Depéret |first=Charles. |year=1896 |title=Note sur les Dinosauriens Sauropodes et Théropodes du Crétacé supérieur de Madagascar |language=French |journal=Bulletin de la Société Géologique de France |volume=21 |pages=176–194}}</ref> This name is derived from the [[Latin]] word ''crenatus'' ("notched") and the [[suffix]] ''-issimus'' ("most"), in reference to the numerous serrations on both front and rear edges of the teeth.<ref name=krauseetal2007/> Depéret later reassigned the species to the North American genus ''[[Dryptosaurus]]'', another poorly-known taxon.<ref name=deperetsavornin1928>{{cite_journal |last=Depéret |first=Charles |coauthors=& Savornin, Justin. |year=1928 |title=La faune de Reptiles et de Poissons albiens de Timimoun (Sahara algérien) |journal=Bulletin de la Societé Géologique de France |volume=27 |pages=257–265}}</ref>
[[Image:P1050192 - Majungatholus.JPG|right|thumb|The [[type specimen]] of ''Majungatholus'': a ''Majungasaurus'' [[frontal bone|frontal]] horn misidentified as a [[pachycephalosaur]] dome ([[Muséum National d'Histoire Naturelle|MNHN]].MAJ 1)]]
Numerous fragmentary remains from [[Mahajanga Province]] in northwestern Madagascar were recovered by French collectors over the next 100 years, many of which were deposited in the [[Muséum National d'Histoire Naturelle]] in [[Paris]].<ref name=krauseetal2007/> In 1955, [[René Lavocat]] described a theropod dentary with teeth from the [[Maevarano Formation]] in the same region where the original material was found. The teeth matched those first described by Depéret, but the strongly curved jaw bone was very different from both ''Megalosaurus'' and ''Dryptosaurus''. Lavocat renamed the genus ''Majungasaurus'', using an older spelling of Mahajanga as well as the [[Greek language|Greek]] word ''σαυρος/sauros'' (meaning "lizard"), and made this jaw bone ([[Muséum National d'Histoire Naturelle|MNHN]].MAJ 1) the [[type specimen]].<ref name=lavocat1955>{{cite_journal |last=Lavocat |first=René |year=1955 |title=Sur une portion de mandibule de Théropode provenant du Crétacé supérieur de Madagascar |journal=Bulletin du Muséum National d’Histoire Naturelle |volume=27 |pages=256–259}}</ref> [[Hans-Dieter Sues]] and [[Philippe Taquet]] described a dome-shaped skull fragment (MNHN.MAJ 4) as a new genus of pachycephalosaur (''Majungatholus atopus'') in 1979. This was the first report of a pachycephalosaur in the Southern Hemisphere.<ref name=suestaquet1979>{{cite_journal |last=Sues |first=Hans-Dieter |coauthors=& Taquet, Phillipe. |year=1979 |title=A pachycephalosaurid dinosaur from Madagascar and a Laurasia−Gondwanaland connection in the Cretaceous |journal=Nature |volume=279 |issue=5714 |pages=633–635 |doi=10.1038/279633a0}}</ref>
In 1993, scientists from the [[State University of New York at Stony Brook]] and the [[University of Antananarivo]] began the Mahajanga Basin Project, a series of expeditions to examine the fossils and geology of the [[Late Cretaceous]] sediments near the village of Berivotra, in Mahajanga Province.<ref name=krauseetal2007/> The first expedition turned up hundreds of theropod teeth identical to those of ''Majungasaurus'', some of which were attached to an isolated premaxilla that was described in 1996.<ref name=sampsonetal1996>{{cite_journal |last=Sampson |first=Scott D. |coauthors=Krause, David W.; [[Peter Dodson|Dodson, Peter]]; & Forster, Catherine A. |year=1996 |title=The premaxilla of Majungasaurus (Dinosauria: Theropoda), with implications for Gondwanan paleobiogeography |journal=Journal of Vertebrate Paleontology |volume=16 |issue=4 |pages=601–605 |url=http://www.vertpaleo.org/publications/jvp/contents-16-4.cfm}}</ref> The following seven expeditions would turn up tens of thousands of fossils, many of which belonged to species new to science. The Mahajanga Basin Project claims credit for quintupling the known diversity of fossil taxa in the region.<ref name=krauseetal2007/>
Fieldwork in 1996 turned up a spectacularly complete theropod skull preserved in exquisite detail ([[Field Museum of Natural History|FMNH]] PR 2100). On top of this skull was a dome-shaped swelling nearly identical to the one described by Sues and Taquet as ''Majungatholus atopus''. ''Majungatholus'' was redescribed as an abelisaurid rather than a pachycephalosaur in 1998. Although the name ''Majungasaurus crenatissimus'' was older than ''Majungatholus atopus'', the authors judged the type dentary of ''Majungasaurus'' too fragmentary to confidently assign to the same species as the skull.<ref name=sampsonetal1998>{{cite_journal |last=Sampson |first=Scott D. |coauthors=Witmer, Lawrence M.; Forster, Catherine A.; Krause, David W.; O'Connor, Patrick M.; [[Peter Dodson|Dodson, Peter]]; & Ravoavy, Florent. |year=1998 |title=Predatory dinosaur remains from Madagascar: implications for the Cretaceous biogeography of Gondwana |journal=Science |volume=280 |issue=5346 |pages=1048–1081 |doi=10.1126/science.280.5366.1048}}</ref> Further fieldwork over the next decade turned up a series of less complete skulls, as well as dozens of partial skeletons of individuals ranging from juveniles to adults. Project members also collected hundreds of isolated bones and thousands of shed ''Majungasaurus'' teeth. Taken together, these remains represent nearly all the bones of the skeleton, although most of the forelimbs, most of the [[pelvis]] and the tip of the tail are still unknown.<ref name=krauseetal2007/> This fieldwork culminated in a 2007 [[monograph]] consisting of seven [[scientific paper]]s on all aspects of the animal's biology, published in the ''[[Society of Vertebrate Paleontology]] Memoirs''. The papers are in [[English language|English]], although each has an [[abstract (summary)|abstract]] written in [[Malagasy]].<ref name=majungamemoir>{{cite_book |last=Sampson |first=Scott D. |coauthors=& Krause, David W. (eds.). |year=2007 |title=''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar |series=Society of Vertebrate Paleontology Memoir '''8''' |pages=184pp |url=http://www.bioone.org/perlserv/?request=get-toc&issn=0272-4634&volume=27&issue=sp8}}</ref> In this volume, the dentary described by Lavocat was re-evaluated and determined to be diagnostic for this species. Therefore, the name ''Majungatholus'' was replaced by the older name ''Majungasaurus''.<ref name=krauseetal2007/> Although the monograph is comprehensive, the editors noted that it describes only material recovered from 1993 through 2001. A significant quantity of specimens, some very complete, were excavated in 2003 and 2005 and await preparation and description in future publications.<ref name=krauseetal2007/>
==Paleobiology==
===Skull ornamentation===
''Majungasaurus'' is perhaps most distinctive for its skull ornamentation, including the swollen and fused nasals and the frontal horn. Other ceratosaurs, including ''Carnotaurus'', ''Rajasaurus'', and ''[[Ceratosaurus]]'' itself bore crests on the head. These structures are likely to have played a role in [[intraspecific competition]], although their exact function within that context is unknown. The hollow cavity inside the frontal horn of ''Majungasaurus'' would have weakened the structure and probably precluded its use in direct physical combat, although the horn may have served a [[Display (zoology)|display]] purpose.<ref name=tykoskirowe2004/> While there is variation in the ornamentation of ''Majungasaurus'' individuals, there is no evidence for [[sexual dimorphism]].<ref name=sampsonwitmer2007/>
===Feeding behavior===
Scientists have suggested that the unique skull shape of ''Majungasaurus'' and other abelisaurids indicate different predatory habits than other theropods. Whereas most theropods were characterized by long, low skulls of narrow width, abelisaurid skulls were taller and wider, and often shorter in length as well.<ref name=sampsonwitmer2007/> The narrow skulls of other theropods were well-equipped to withstand the vertical stress of a powerful bite, but not as good at withstanding [[Torsion (mechanics)|torsion]] (twisting).<ref name=rayfieldetal2001>{{cite_journal |last=Rayfield |first=Emily |coauthors=[[David B. Norman|Norman, David B.]]; Horner, Celeste C.; [[Jack Horner (paleontologist)|Horner, John R.]]; Smith, Paula M.; Thomason, Jeffrey J.; & Upchurch, Paul. |year=2001 |title=Cranial design and function in a large theropod dinosaur |journal=Nature |volume=409 |issue=6823 |pages=1033–1037 |doi=10.1038/35059070}}</ref> In comparison to modern [[carnivora|mammalian predators]], most theropods may have used a strategy similar in some ways to that of long- and narrow-snouted [[canid]]s, with the delivery of many bites weakening the prey animal.<ref name=vanvalkenburghmolnar2002>{{cite_journal |last=Van Valkenburgh |first=Blaire |coauthors=& [[Ralph Molnar|Molnar, Ralph E.]] |year=2002 |title=Dinosaurian and mammalian predators compared |journal=Paleobiology |volume=28 |issue=4 |pages=527–543 |url=http://paleobiol.geoscienceworld.org/cgi/content/abstract/28/4/527 |doi=10.1666/0094-8373(2002)028<0527:DAMPC>2.0.CO;2 |doilabel=10.1666/0094-8373(2002)028<0527:DAMPC>2.0.CO;2}}</ref>
[[Image:Majungasaurus DB.jpg|thumb|right|''Majungasaurus crenatissimus'']]
Abelisaurids, especially ''Majungasaurus'', may instead have been adapted for a feeding strategy more similar to modern [[felid]]s, with short and broad snouts, that bite once and hold on until the prey is subdued. ''Majungasaurus'' had an even broader snout than other abelisaurids, and other aspects of its anatomy may also support the bite-and-hold hypothesis. The neck was strengthened, with robust vertebrae, interlocking ribs and ossified tendons, as well as reinforced muscle attachment sites on the vertebrae and the back of the skull. These muscles would have been able to hold the head steady despite the struggles of its prey. Abelisaurid skulls were also strengthened in many areas by bone [[mineralization (biology)|mineralized]] out of the [[skin]], creating the characteristic rough texture of the bones. This is particularly true of ''Majungasaurus'', where the nasal bones were fused and thickened for strength. On the other hand, the lower jaw of ''Majungasaurus'' sported a large [[fenestra]] (opening) on each side, as seen in other ceratosaurs, as well as [[synovial joint]]s between certain bones that allowed a high degree of flexibility in the lower jaw, although not to the extent seen in [[snake]]s. This may have been an adaptation to prevent the fracture of the lower jaw when holding onto a struggling prey animal. The front teeth of the upper jaw were more robust than the rest, to provide an anchor point for the bite, while the low crown height of ''Majungasaurus'' teeth prevented them from breaking off during a struggle. Finally, unlike the teeth of ''[[Allosaurus]]'' and most other theropods, which were curved on both the front and back, abelisaurids like ''Majungasaurus'' had teeth curved on the front edge but straighter on the back (cutting) edge. This structure may have served to prevent slicing, and instead holding the teeth in place when biting.<ref name=sampsonwitmer2007/>
''Majungasaurus'' was the largest predator in its environment, while the only known large herbivores at the time were sauropods like ''Rapetosaurus''. Scientists have suggested that ''Majungasaurus'', and perhaps other abelisaurids, specialized on hunting sauropods. Adaptations to strengthen the head and neck for a bite-and-hold type of attack might have been very useful against sauropods, which would have been tremendously powerful animals. This hypothesis may also be supported by the hindlegs of ''Majungasaurus'', which were short and stocky, as opposed to the longer and more slender legs of most other theropods. While ''Majungasaurus'' would not have moved as fast as other similar-sized theropods, it would have had no trouble keeping up with slow-moving sauropods. The robust hindlimb bones suggest very powerful legs, and their shorter length would have lowered the animal's center of gravity. Thus ''Majungasaurus'' may have sacrificed speed for power.<ref name=sampsonwitmer2007/> ''Majungasaurus'' tooth marks on ''Rapetosaurus'' bones confirm that it at least fed on these sauropods, whether or not it actually killed them.<ref name=rogersetal2003>{{cite_journal |last=Rogers |first=Raymond R. |coauthors=Krause, David W.; & [[Kristina Curry Rogers|Curry Rogers, Kristina]]. |year=2007 |title=Cannibalism in the Madagascan dinosaur ''Majungatholus atopus'' |journal=Nature |volume=422 |issue=6931 |pages=515–518 |doi=10.1038/nature01532}}</ref>
===Cannibalism===
Although sauropods may have been the prey of choice for ''Majungasaurus'', recent discoveries in Madagascar indicate another surprising component of its diet: other ''Majungasaurus''. Numerous bones of ''Majungasaurus'' have been discovered bearing tooth marks identical to those found on sauropod bones from the same localities. These marks have the same spacing as teeth in ''Majungasaurus'' jaws, are of the same size as ''Majungasaurus'' teeth, and contain smaller notches consistent with the serrations on those teeth. As ''Majungasaurus'' is the only large theropod known from the area, the simplest explanation is that it was feeding on other members of its own species.<ref name=rogersetal2003/> Suggestions that the [[Triassic]] ''[[Coelophysis]]'' was a cannibal have been recently disproven, leaving ''Majungasaurus'' as the only non-avian theropod with confirmed cannibalistic tendencies,<ref name="nesbittetal2006">{{cite_journal |last=Nesbitt |first=Sterling J. |coauthors=Turner, Alan H.; Erickson, Gregory M.; & Norell, Mark A. |year=2006 |title=Prey choice and cannibalistic behavior in the theropod ''Coelophysis'' |journal=Biology Letters |volume=2 |issue=4 |pages=611–614 |doi=10.1098/rsbl.2006.0524}}</ref> although there is some evidence that cannibalism may have occurred in other species as well.<ref name=roachbrinkman2007>{{cite_journal |last=Roach |first=Brian T. |coauthors=& Brinkman, Daniel T. |year=2007 |title=A reevaluation of cooperative pack hunting and gregariousness in ''Deinonychus antirrhopus'' and other non-avian theropod dinosaurs |journal=Bulletin of the Peabody Museum of Natural History |volume=48 |issue=1 |pages=103–138 |url=http://web.archive.org/web/20070810172000/http://www.peabody.yale.edu/scipubs/abstracts/abs_b48-1b.html |doi=10.3374/0079-032X(2007)48[103:AROCPH]2.0.CO;2|doilabel=10.3374/0079-032X(2007)48[103:AROCPH]2.0.CO;2}}</ref>
It is unknown if ''Majungasaurus'' actively hunted their own kind or only [[scavenger|scavenged]] their carcasses.<ref name=rogersetal2003/> However, some researchers have noted that modern [[Komodo monitor]]s sometimes kill each other when competing for access to carcasses. The [[lizard]]s will then proceed to cannibalize the remains of their rivals, which may suggest similar behavior in ''Majungasaurus'' and other theropods.<ref name=roachbrinkman2007/>
===Respiratory system===
Scientists have reconstructed the [[respiratory system]] of ''Majungasaurus'' based on a superbly-preserved series of vertebrae ([[University of Antananarivo|UA]] 8678) recovered from the Maevarano Formation. Most of these vertebrae and some of the ribs contained cavities (pneumatic [[Foramen|foramina]]) that may have resulted from the infiltration of [[Bird|avian]]-style [[Bird anatomy#Respiratory system|lungs and air sacs]]. In birds, the neck vertebrae and ribs are hollowed out by the cervical air sac, the upper back vertebrae by the [[lung]], and the lower back and [[sacrum|sacral]] (hip) vertebrae by the abdominal air sac. Similar features in ''Majungasaurus'' vertebrae imply the presence of these air sacs. These air sacs may have allowed for a basic form of avian-style 'flow-through ventilation,' where air flow through the lungs is one-way, so that [[oxygen]]-rich air inhaled from outside the body is never mixed with exhaled air laden with [[carbon dioxide]]. This method of respiration, while complicated, is highly efficient.<ref name=oconnorclaessens2006>{{cite_journal |last=O'Connor |first=Patrick M. |coauthors=& Claessens, Leon P.A.M. |year=2006 |title=Basic avian pulmonary design and flow-through ventilation in non-avian theropod dinosaurs |journal=Nature |volume=436 |issue=7048 |pages=253–256 |doi=10.1038/nature03716}}</ref>
The recognition of pneumatic foramina in ''Majungasaurus'', besides providing an understanding of its respiratory biology, also has larger-scale implications for evolutionary biology. The split between the ceratosaur line, which led to ''Majungasaurus'', and the [[tetanurae|tetanuran]] line, to which birds belong, occurred very early in the history of theropods. The avian respiratory system, present in both lines, must therefore have evolved before the split, and well before the evolution of birds themselves. This provides further evidence of the dinosaurian [[origin of birds]].<ref name=oconnorclaessens2006/>
===Brain and inner ear structure===
[[Computed tomography]], also known as CT scanning, of a complete ''Majungasaurus'' skull (FMNH PR 2100) allowed a rough reconstruction of its [[brain]] and [[inner ear]] structure. Overall, the brain was very small relative to body size, but otherwise similar to many other non-[[coelurosauria]]n theropods, with a very conservative form closer to modern [[crocodilia]]ns than to birds. One difference between ''Majungasaurus'' and other theropods was its smaller [[Flocculus (cerebellar)|flocculus]], a region of the [[cerebellum]] that helps to coordinate movements of the [[eye]] with movements of the head. This suggests that ''Majungasaurus'' and other abelisaurids like ''[[Indosaurus]]'', which also had a small flocculus, did not rely on quick head movements to sight and capture prey.<ref name=sampsonwitmer2007/>
Inferences about behavior can also be drawn from examination of the inner ear. The [[semicircular canal]]s within the inner ear aid in balance, and the [[lateral semicircular canal]] is usually parallel to the ground when the animal holds its head in an alert posture. When the skull of ''Majungasaurus'' is rotated so that its lateral canal is parallel to the ground, the entire skull is nearly horizontal. This contrasts with many other theropods, where the head was more strongly downturned when in the alert position. The lateral canal is also significantly longer in ''Majungasaurus'' than in its more [[basal (phylogenetics)|basal]] relative ''[[Ceratosaurus]]'', indicating a greater sensitivity to side-to-side motions of the head.<ref name=sampsonwitmer2007/>
===Pathology===
A 2007 report described [[pathology|pathologies]] in the bones of ''Majungasaurus''. Scientists examined the remains of at least 21 individuals and discovered four with noticeable pathologies.<ref name=farkeoconnor2007>{{cite_book |last=Farke |first=Andrew A. |coauthors=& O'Connor, Patrick M. |year=2007 |chapter=Pathology in ''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar |editor=Sampson, Scott D.; & Krause, David W. (eds.) |title=''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar |series=Society of Vertebrate Paleontology Memoir '''8''' |pages=180–184 |url=http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1671%2F0272-4634%282007%2927%5B180%3APIMCTA%5D2.0.CO%3B2}}</ref> While pathology had been studied in large [[tetanurae|tetanuran]] theropods like [[allosaurid]]s and [[tyrannosaurid]]s,<ref name=rothschildtanke2005>{{cite_book |last=Rothschild |first=Bruce |coauthors=& [[Darren Tanke|Tanke, Darren H.]] |year=2005 |chapter=Theropod paleopathology: state-of-the-art review |editor=[[Ken Carpenter|Carpenter, K.]] (ed.) |title=The Carnivorous Dinosaurs |location=Bloomington |publisher=Indiana University Press |pages=351–365 |isbn=978-0253345394}}</ref> this was the first time an abelisauroid had been examined in this manner. No wounds were found on any skull elements, in contrast to tyrannosaurids where sometimes gruesome facial bites were common. One of the specimens was a [[Phalanx bones|phalanx]] (toe bone) of the foot, which had apparently been broken and subsequently healed.<ref name=farkeoconnor2007/>
Most of the pathologies occurred on the vertebrae. For example, a dorsal (back) vertebra from a juvenile animal showed an [[exostosis]] (bony growth) on its underside. The growth probably resulted from the conversion of [[endochondral ossification|cartilage]] or a [[ligament]] to bone during development, but the cause of the ossification was not determined. [[Hypervitaminosis A]] and [[bone spur]]s were ruled out, and an [[osteoma]] (benign bone tumor) was deemed unlikely. Another specimen, a small caudal (tail) vertebra, was also found to have an abnormal growth, this time on the top of its [[spinous process|neural spine]], which projects upwards from the vertebrae, allowing muscle attachment.<ref name=farkeoconnor2007/> Similar growths from the neural spine have been found in specimens of ''Allosaurus''<ref name=hanna2002>{{cite_journal |last=Hanna |first=Rebecca R. |year=2002 |title=Multiple injury and infection in a sub-adult theropod dinosaur ''Allosaurus fragilis'' with comparisons to allosaur pathology in the Cleveland-Lloyd Dinosaur Quarry collection |journal=Journal of Vertebrate Paleontology |volume=22 |issue=1 |pages=76–90 |url=http://www.vertpaleo.org/publications/jvp/22-076-090.cfm |doi=10.1671/0272-4634(2002)022[0076:MIAIIA]2.0.CO;2 |doilabel=10.1671/0272-4634(2002)022[0076:MIAIIA]2.0.CO;2}}</ref> and ''Masiakasaurus'', probably resulting from the ossification of a ligament running either between the neural spines ([[interspinal ligament]]) or along their tops ([[supraspinal ligament]]).<ref name=farkeoconnor2007/>
The most serious pathology discovered was in a series of five large tail vertebrae. The first two vertebrae showed only minor abnormalities with the exception of a large groove that extended along the left side of both bones. However, the next three vertebrae were completely fused together at many different points, forming a solid bony mass. There is no sign of any other vertebrae after the fifth in the series, indicating that the tail ended there prematurely. From the size of the last vertebrae, scientists judged that about ten vertebrae were lost. One explanation for this pathology is severe [[physical trauma]] resulting in the loss of the tail tip, followed by [[osteomyelitis]] (infection) of the last remaining vertebrae. Alternatively, the infection may have come first and led to the end of the tail becoming [[necrosis|necrotic]] and falling off. This is the first example of tail truncation known in a non-avian theropod dinosaur.<ref name=farkeoconnor2007/>
==Paleoecology==
[[Image:MG-Mahajanga.png|right|125px|thumb|All ''Majungasaurus'' fossils have been found in the [[Mahajanga Province]] of [[Madagascar]], most within 50 kilometers (30 miles) to the southeast of the provincial capital, [[Mahajanga]] (marked with a red dot on the map).]]
All specimens of ''Majungasaurus'' have been recovered from the Maevarano Formation in the [[Mahajanga Province]] in northwestern Madagascar. Most of these, including all of the most complete material, came from the Anembalemba Member, although ''Majungasaurus'' teeth have also been found in the underlying Masorobe Member and the overlying Miadana Member. While these sediments have not been dated [[radiometric dating|radiometrically]], evidence from [[biostratigraphy]] and [[paleomagnetism]] suggest that they were deposited during the [[Maastrichtian]] [[faunal stage|stage]], which lasted from 70 to 65 Ma (million years ago). ''Majungasaurus'' teeth are found up until the very end of the Maastrichtian, when all non-avian dinosaurs [[Cretaceous–Tertiary extinction event|went extinct]].<ref name=rogersetal2007>{{cite_book |last=Rogers |first=Raymond R. |coauthors=Krause, David W.; [[Kristina Curry Rogers|Curry Rogers, Kristina]]; Rasoamiaramanana, Armand H.; & Rahantarisoa, Lydia. |year=2007 |chapter=Paleoenvironment and Paleoecology of ''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar |editor=Sampson, Scott D.; & Krause, David W. (eds.) |title=''Majungasaurus crenatissimus'' (Theropoda: Abelisauridae) from the Late Cretaceous of Madagascar |series=Society of Vertebrate Paleontology Memoir '''8''' |pages=21–31 |url=http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1671%2F0272-4634%282007%2927%5B21%3APAPOMC%5D2.0.CO%3B2}}</ref>
Then as now, Madagascar was an island, having [[plate tectonics|separated]] from the [[Indian subcontinent]] less than 20 million years earlier. It was drifting northwards but still 10–15[[Degree (angle)|°]] more southerly in [[latitude]] than it is today. The prevailing [[climate]] of the time was semi-arid, with pronounced [[season]]ality in temperature and rainfall. ''Majungasaurus'' inhabited a coastal [[flood plain]] cut by many sandy [[river]] [[Channel (geography)|channels]].<ref name=rogersetal2007/> Strong geological evidence suggests the occurrence of periodic [[debris flow]]s through these channels at the beginning of the wet season, burying the carcasses of organisms killed during the preceding dry season and providing for their exceptional preservation as fossils.<ref name=rogers2005>{{cite_journal |last=Rogers |first=Raymond R. |year=2005 |title=Fine-grained debris flows and extraordinary vertebrate burials in the Late Cretaceous of Madagascar |journal=Geology |volume=33 |issue=4 |pages=297–300 |doi=10.1130/G21036.1}}</ref> Sea levels in the area were rising throughout the Maastrichtian, and would continue to do so into the [[Paleocene Epoch]], so ''Majungasaurus'' may have roamed coastal environments like [[tidal flats]] as well. The neighboring [[Berivotra Formation]] represents the contemporaneous [[Marine (ocean)|marine]] environment.<ref name=rogersetal2007/>
Besides ''Majungasaurus'', fossil taxa recovered from the Maevarano include [[fish]], [[frog]]s, lizards, snakes,<ref name=rogersetal2007/> seven distinct species of [[crocodylomorph]]s,<ref name=krauseetal2006>{{cite_journal |last=Krause |first=David W. |coauthors=O'Connor, Patrick M.; [[Kristina Curry Rogers|Curry Rogers, Kristina]]; Sampson, Scott D.; Buckley, Gregory A.; & Rogers, Raymond R. |year=2006 |title=Late Cretaceous terrestrial vertebrates from Madagascar: implications for Latin American biogeography |journal=Annals of the Missouri Botanical Gardens |volume=93 |issue=2 |pages=178–208 |url=http://www.mbgpress.info/index.php?task=id&id=11002 |doi=10.3417/0026-6493(2006)93[178:LCTVFM]2.0.CO;2 |doilabel=10.3417/0026-6493(2006)93[178:LCTVFM]2.0.CO;2}}</ref> five or six species of [[mammal]]s,<ref name=krauseetal2006/> ''[[Vorona]]''<ref name=forsteretal1996>{{cite_journal |last=Forster |first=Catherine A. |coauthors=Chiappe, Luis M.; Krause, David W.; & Sampson, Scott D. |title=The first Cretaceous bird from Madagascar |journal=Nature |volume=382 |issue=6591 |pages=532–534 |doi=10.1038/382532a0 |year=1996}}</ref> and several other birds,<ref name=rogersetal2007/> the possibly flighted [[dromaeosaurid]] ''[[Rahonavis]]'',<ref name=forsteretal1998>{{cite_journal |last=Forster |first=Catherine |coauthors=Sampson, Scott D.; Chiappe, Luis M.; & Krause, David W. |year=1998 |title=The theropod ancestry of birds: new evidence from the Late Cretaceous of Madagascar |journal=Science |volume=279 |issue=5358 |pages=1915–1919 |doi=10.1126/science.279.5358.1915}}</ref><ref name=makovickyetal2005>{{cite_journal |last=Makovicky |first=Peter J. |coauthors=Apesteguía, Sebastian; & Agnolín, Federico L. |year=2005 |title=The earliest dromaeosaurid theropod from South America |journal=Nature |volume=437 |issue=7061 |pages=1007–1011 |doi=10.1038/nature03996}}</ref> the noasaurid ''Masiakasaurus''<ref name=sampsonetal2001>{{cite_journal |last=Sampson |first=Scott D. |coauthors=Carrano, Matthew T.; & Forster, Catherine A. |year=2001 |title=A bizarre predatory dinosaur from the Late Cretaceous of Madagascar |journal=Nature |volume=409 |issue=6819 |pages=504–506 |doi=10.1038/35054046}}</ref> and two [[titanosauria]]n sauropods, including ''Rapetosaurus''.<ref name=curryrogersforster2001>{{cite_journal |last=Curry Rogers |first=Kristina |authorlink=Kristina Curry Rogers |coauthors=& Forster, Catherine A. |year=2001 |title=The last of the dinosaur titans: a new sauropod from Madagascar |journal=Nature |volume=412 |issue=6846 |pages=530–534 |doi=10.1038/35087566}}</ref> ''Majungasaurus'' was by far the largest carnivore and probably the dominant predator on land, although large crocodylomorphs like ''[[Mahajangasuchus]]'' and ''[[Trematochampsa]]'' might have competed with it closer to water.<ref name=rogersetal2007/>
==References==
{{reflist|2}}
==External links==
{{portalpar|Dinosaurs}}
*''Majungasaurus'' [http://web.archive.org/web/20060715234157/http://students.washington.edu/eoraptor/Ceratosauria.htm#Majungasauruscrenatissimus entry] in [http://web.archive.org/web/20061021204603/http://students.washington.edu/eoraptor/Home.html The Theropod Database].
<!--*''Majungasaurus'' [http://www.paleograveyard.com/majungatholus.html skull images] at The Grave Yard.-->
*[http://commcgi.cc.stonybrook.edu/artman/publish/article_1090.shtml Press release] about the ''Majungasaurus'' mount erected in 2006 at SUNY - Stony Brook.
{{featured article}}
[[Category:Ceratosaurs]]
[[Category:Cretaceous dinosaurs]]
[[Category:Dinosaurs of India and Madagascar]]
[[Category:Maevarano fauna]]
[[cs:Majungasaurus]]
[[es:Majungasaurus]]
[[it:Majungasaurus crenatissimus]]
[[ja:マジュンガトルス]]
[[pl:Majungazaur]]
[[ru:Майюнгазавр]]
[[zh:瑪君龍]]