Majungasaurus (Mahajanga Lizard) is a genus of abelisaurid theropod dinosaur that served as the apex predator of the Maevarano Formation in the Mahajanga Province (known as "Majunga" in French) of northwest Madagascar, 70 - 66 million years ago, during the Maastrichtian stage of the Late Cretaceous Period. It is often recognized for being one of the few confirmed cannibal dinosaurs, though they may not have engaged in such behavior in normal conditions.[7]
Majungasaurus was not a fast hunter, so it more likely relied on ambushing and cornering its prey
Majungasaurus is a medium-sized, heavily-built abelisaurid that stood 2 meters (6 feet, 7 inches) tall and 5.6 - 7 meters (18 - 23 feet) in length,[2] with some fragmentary remains indicating that some specimens can exceed 8 meters (26 feet), rivaling Carnotaurus in length. It weighed around 750 - 1,100 kilograms (1,650 - 2,430 pounds).[1] Unlike Carnotaurus, which had long, gracile legs that gave it a top speed of around 48 - 56 kilometers (30 - 35 miles) per hour,[8]Majungasaurus and its Indian relative Rajasaurus have short legs that indicated that they were slower predators that relied more on ambush, though they may still have been able to accelerate quickly to pursue prey.[9]
Unlike their noasaurid cousins, which retained long forelimbs with well-developed claws, abelisaurids had robust but short arms with immobile elbow joints, no carpalia (wrist bones), metacarpals (palm bones) attached directly to the forearm, and four fused fingers which bear evidence of neither ungual bones nor the grooves and pits of tendon attachments,[10][11] hence, all three of the abelisaurids featured on Prehistoric Planet are portrayed without claws on all four of their immobile fingers. It has been suggested that, at some point in their evolutionary history, the abelisaurid family suffered a genetic defect that caused their HOXA11 and HOXD11 genes (both of which regulate the development of forelimbs) to lose functionality, which resulted in their arms eventually being reduced to stubs, with the entire forelimb past the elbow possibly being vestigial in nature, as the nerve fibers responsible for the transmission of stimuli in these limbs are as reduced as those of emus and kiwis, which bear vestigial wings.[12][10][11][13]
Growth[]
To survive the arid conditions of Madagascar, Majungasaurus grew slowly, reaching its maximum size in 20 years
Animals found in impoverished environments tend to grow slower in order to reduce the cost of maintaining and nourishing themselves. Having lived in the semi-arid and seasonally stressful environment of the Maevarano Formation (which can, in turn, result in a scarcity of food, water, and various other resources, which can push an animal to turn to cannibalism), Majungasaurus likely evolved slow growth to ensure better chances of survival, as it took 20 years to reach maturity.[6] For similar reasons, Masiakasaurus, a small theropod that lived in the same area, took 8 - 10 years to fully grow, a rate 40% slower than other non-avian theropod dinosaurs of similar size, but 40% faster than crocodylians.[14] As indicated by several well-preserved specimens of different ages, when a Majungasaurus grows, its skull becomes taller and more robust as the bones fused together to form stronger connections, while its eye sockets gradually decrease in size, indicating that, like T. rex, there was a significant gap between juveniles and adults in terms of the skull's biomechanical properties and the individual's feeding preferences.[15] Both apex predators also only coexisted with significantly smaller theropods that have no chance of competing against the adults. It is therefore reasonable to assume that, similar to T. rex, young Majungasaurus occupied the mesopredator role of their respective ecosystems, taking up the otherwise empty niche between the apex predator role of adult Majungasaurus and the niche occupied by the smaller theropods.
Brain, Senses, and Vocalizations[]
Majungasaurus growls in frustration after the Simosuchus she cornered successfully got in a hole
A 2007 CT scan of the complete skull of Majungasaurus specimen FMNH PR 2100 revealed that Majungasaurus has a braincase volume of 106.4 cubic centimeters (6.5 cubic inches), with the brain assumed to take up 50% of that space. Unlike Carnotaurus and South American abelisaurs, which have large flocculi (the brain lobe responsible for gaze stabilization), Majungasaurus and relatives like Indosaurus of India have small flocculi.[16] The diminished size of the flocculus indicates poor coordination of eye movement with head, neck, and body movement, meaning that Majungasaurus did not rely on quick head and body movements to pinpoint prey or other matters of interest. The anatomy of the inner ear of Majungasaurus also implies certain behavioral traits. When an animal holds its head in an alert posture, its lateral semicircular canals (which help aid in balance) would be parallel to the ground. Given this, many theropods have their heads turned down when they are in an alert position. This makes Majungasaurus unusual among theropods, since it assumes its alert posture when its head is held in an almost-horizontal position, with the theory being that it elevated its snout and held its head in this way so that the rough features on its nose would not significantly obstruct its binocular field of view. And while Majungasaurus is not reliant on quickly moving its head and body to help locate and focus on targets, its lateral canal is still significantly longer than that of its more basal relative Ceratosaurus, indicating that it might be more sensitive to lateral head motion.[4]
Abelisaurs also possess a poor sense of hearing due to their short lagena (upper extremity of the cochlear duct),[16] hence, Majungasaurus would have had to rely more on detecting low-frequency sounds, and thus likely communicated with low vocalizations. As with Carnotaurus and Rajasaurus, Prehistoric Planet portrays Majungasaurus making guttural crocodile-like sounds and emu-esque vocalizations, producing low, rumbling growls and resonant, raspy huffs. Much like birds, crocodiles, and other reptiles, Majungasaurus does not need to open its mouth in order to vocalize, as vibrating and amplifying the sound of air within the body is sufficient.
Jaws and Dentition[]
Majungasaurus had a wider skull compared to other abelisaurs, fit for gripping prey, but not for prying through burrows, crevices, or other narrow openings
The skull of Majungasaurus is short, measuring approximately 60 - 70 centimeters (2 feet - 2 feet, 4 inches) in length, yet tall and robust. like the heads of other abelisaurs. However, it is not as short as the skull of Carnotaurus, and it is wider compared to those of other abelisaurs.[3] According to a study in 2018, abelisaurs may have had a bite force similar to that of Allosaurus, with one abelisaur, Carnotaurus, having an estimated bite force of around 3,341 newtons or 340 kilograms (750 pounds). It is believed that, as with Allosaurus, abelisaurs used their weak bites with their reinforced skulls and strong, muscular necks to be able to withstand the stresses of repeatedly grabbing and pulling on large prey like the sauropods they coexisted with.[9] Conversely, estimates made in 2022, based off of phylogenetically predicted physiological cross-sectional areas of jaw adductor muscles, suggest higher bite forces for both Allosaurus and abelisaurids; a Majungasaurus with a skull width of 30 centimeters (12 inches) likely exerted around 3,140 newtons or 320 kilograms (706 pounds) in the front of its jaws, and 7,845 newtons or 800 kilograms (1,764 pounds) in the back of its jaws. By comparison, the same study suggests that a Carnotaurus with a skull width of 30 centimeters (12 inches) likely exerted around 3,400 newtons or 350 kilograms (764 pounds) in the front of its jaws, and 7,172 newtons or 732 kilograms (1,612 pounds) in the back of its jaws.[5]
Rugged Features[]
Majungasaurus observes prey from a distance
As an abelisaur, Majungasaurus had rough skin, made even more rugged by protuberances randomly scattered and distributed all over the body. These subconical bumps and studs, fitting the definition of what is known as "feature scales" (specifically of the shield type), lack bony cores or any sort of ossification, and thus cannot be considered as osteoderms.[17][18][19][20] It is believed that the rough skin of abelisaurs may have helped these large, highly-active, warm-blooded predators to shed excess heat from their bodies, similar to the integument of living reptiles and mammals.[19]
Atop the theropod's skull, compact and robust like those of other abelisaurs, is a single thick, rounded horn. Originally, this horn was mistaken for a pachycephalosaur dome in 1979,[21] and was thus considered a new pachycephalosaur called "Majungatholus atopus". However, its true origin was eventually discovered in 1998, leading to a reversion to its older name, "Majungasaurus crenatissimus", which was set in 1955, around 24 years prior to "Majungatholus",[22] and thus takes precedence. It is now believed that this rounded horn was likely a display feature (since the horn has a hollow sinus cavity within it, making it not ideal for use in physical headbutting). This single horn, along with other shared features, shows that Majungasaurus is more closely related to Rajasaurus of India rather than Carnotaurus of Argentina, reinforcing the belief that the abelisaurs of Africa, Europe, and India diverged into forms distinct from their isolated South American cousins. Unlike Rajasaurus, however, the horn of Majungasaurus is made of frontal bone more than nasal bone, with the inverse is true for Rajasaurus.[4]
Prehistoric Planet's Portrayal[]
Majungasaurus concept art by Gabriel N. Ugueto
“ This particular female is blind in one eye. So she finds it hard to make a kill, and is now very hungry. ”
Prehistoric Planet depicts Majungasaurus with an earthly-brown color scheme and a body that appears to be lower and more heavily-built than Carnotaurus and Rajasaurus. The only individual seen on the show is a female with wounds on her neck and flank as well as a blind left eye. Dr. Darren Naish, lead consultant of Prehistoric Planet, confirms that this is based on a nearly complete Majungasaurus described in 2020, specimen FMNH PR 2836, which suffered injuries to the face, lower jaw, spine, arm, ribs and belly, likely due to one injury leading to another, which in turn resulted in - and got exacerbated by - infections that compromised the animal's immune system.[23][DN 1] The original plan was to show that these injuries were the result of an attack by a Mahajangasuchus, a crocodyliform that also lived in the Maevarano Formation, though such a scene was ultimately scrapped.[DN 2] Concept art by Gabriel Ugueto also shows that Majungasaurus was, at one point, planned to have more striking skin patterns.[PhP 1]
Majungasaurus abandons the failed hunt for Simosuchus
“ The island of Madagascar has been separated from the African mainland for 80 million years, so long that most of its animals are now very different from any to be found elsewhere. ”
Majungasaurus lived 70 - 66 million years ago in the Maevarano Formation in the Mahajanga Province of Madagascar as the apex predator of the region. The Maevarano Formation is recognized as an alluvial plain where the discharge of rivers fluctuate. The area is also believed to have had reddish soil, with floodplains that supported vegetation able to grow in the relatively dry climate. The region, at times semi-arid (like it is today), at times undergoing strong dry and wet seasons, was eventually claimed by rising sea levels that pushed the shoreline back. This may or may not have been the result of the Cretaceous-Paleogene Extinction Event, a catastrophe that wiped out three-quarters of life on Earth, including all non-avian dinosaurs like Majungasaurus.
Hunting Tactics and Feeding Preferences[]
The wounded face and blind left eye of the female Majungasaurus, based on FMNH PR 2836, a heavily-injured Majungasaurus specimen described in 2020
The female seen on Prehistoric Planet is shown to have dried blood and wounds on her neck and flank, along with a blinded left eye. This implies that she's gotten into an accident or has been involved in conflict (the original plan was to show that these injuries were inflicted by a Mahajangasuchus).[DN 2] Such conflicts can also be the result of the most known trait of the animal as indicated by evidence and popularized in modern media, hostility between members that results in cannibalism.[7] Whatever the case, these wounds and the loss of vision in one eye prove detrimental for the Majungasaurus, who is forced to rely more on ambush for her hunts. Despite being very hungry and thus more motivated and driven to acquire a meal, she is still put off by the bluffs of a Simosuchus, which is able to confuse and deter her long enough to escape into a burrow.
This same female is later seen wandering around at night, likely still unsuccessful in finding a meal. It is unknown if this implies that Majungasaurus is nocturnal, cathemeral (active in irregular intervals during day and night), or is not behaving normally and is just forced to hunt at night due to desperation.
Filming Location Lower Zambezi National Park, Lusaka Province, southeast Zambia[PhP 2]
Majungasaurus observing a group of Simosuchus from afar
In the third segment of Islands, on Madagascar, a Simosuchus navigates through an area of plants. It is then shown that they live in a group. One Simosuchus reaches up to grab leaves that are out of reach by rearing up and standing on top of another, while some members of the group are shown simply basking under the sun, or sleeping in the shade, not too wary of predators given how their heavily-armored bodies make them feel more secure, unaware that, from afar, a female Majungasaurus is observing them. She appears to have dried blood and various wounds on her, and it is revealed that her left eye has gone blind. Due to her disability, she has found it difficult to hunt, and has thus gone very hungry. She finally decides to charge at the group of Simosuchus, causing them to run for the burrows they set up beforehand to escape from predators. One male Simosuchus ends up unable to find an unoccupied burrow, and is left to face the Majungasaurus.
Unable to escape, the Simosuchus stands his ground and tries to make himself appear more threatening to the Majungasaurus with aggressive sounds and actions
“ This little male is unlucky. But he's not helpless. Reverse charges, tail swipes, and aggressive kicks. ”
With nowhere to run, the Simosuchus resorts to bluffing his way out of the situation, with reverse charges, kicks, hisses, and tail swipes, confusing and deterring the Majungasaurus long enough for the male to find a vacant burrow to rush for and hide in. The hunter tries to reach into the burrow, but it proves too narrow for her broad snout to fit in. As a safety precaution, the Simosuchus digs himself even deeper, getting dirt all over the hunter's face.
The Simosuchus digs himself deeper into his burrow, kicking dust into the abelisaur's face
“ The hunter's snout is too broad to reach very far inside. But just to be on the safe side, the Simosuchus digs even deeper. For the Majungasaurus, yet another hunt has ended in failure. ”
Dejected and left growling in frustration due to the failure to secure a meal, the Majungasaurus walks off, with the Simosuchus emerging from his burrow only when he is sure that the hunter has really left the area.
Filming Location Lower Zambezi National Park, Lusaka Province, southeast Zambia[PhP 2]
In the fourth segment of Islands, as an Adalatherium goes out at night to look for food, she comes across the same Majungasaurus from earlier (as indicated by the individual's wounds and blinded left eye). The mammal, possessing poor vision herself, senses the threat with her ears and stays still to avoid getting noticed. Fortunately for the mammal, the theropod remained unaware of her presence, the Majungasaurus briefly sniffing the air before wandering off to continue looking for prey.
Trivia[]
Majungasaurus is the only abelisauroid on Prehistoric Planet not shown interacting with others of its kind, as, unlike Masiakasaurus, Carnotaurus, and Rajasaurus, only one individual, the wounded, half-blind female, is present in the entire series.
Gallery[]
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↑Vargas, A. 2002. "La extrema reducción del radio y la ulna en la evolución de Carnotaurus sastrei: Posible pérdida de función de los genes HOXA11 y HOXD11". Ameghiniana 39: 17R
