Majungasaurus (Mahajanga Lizard)
Basic facts
23 feet (7m) length
Late Cretaceous
Madagascar
Carnivore
Majungasaurus, which translates to "Mahajanga lizard," is a genus of abelisaurid theropod dinosaur that inhabited Madagascar during the Late Cretaceous period, approximately 70 to 66 million years ago. This places it among the last known non-avian dinosaurs, which faced extinction during the Cretaceous-Paleogene event. The genus is home to a single species, Majungasaurus crenatissimus, and is sometimes referred to as Majungatholus, although the latter is considered a junior synonym of Majungasaurus.
Similar to other abelisaurids, Majungasaurus was a bipedal predator characterized by its short snout. While the forelimbs remain incompletely known, they were notably short, contrasting with the longer and robust hind limbs. What sets Majungasaurus apart from other abelisaurids are its broader skull, the heavily textured and thickened bone on the top of its snout, and the presence of a single rounded horn on the roof of its skull. Interestingly, this horn was initially mistaken for the dome of a pachycephalosaur. In addition, Majungasaurus possessed more teeth in both the upper and lower jaws compared to most abelisaurids.
This dinosaur was one of the first abelisaurs to be discovered, with initial findings dating back to 1896 (although originally believed to be a species of Megalosaurus) and its official naming occurring in 1955. With several well-preserved skulls and a wealth of skeletal material, Majungasaurus is now considered one of the most comprehensively studied theropod dinosaurs from the Southern Hemisphere. It's believed to have the closest ties to abelisaurids from India rather than South America or continental Africa, carrying significant biogeographical implications.
As the apex predator in its ecosystem, Majungasaurus primarily preyed on sauropods like Rapetosaurus. Notably, there's direct evidence of cannibalism in Majungasaurus, indicating it consumed other members of its own species. In terms of size, Majungasaurus was a medium-sized theropod, typically reaching lengths of 5.6 to 7 meters (18 to 23 feet) and weighing between 750 to 1,100 kilograms (1,650 to 2,430 pounds). Fragmentary remains suggest some adults could have exceeded 8 meters (26 feet) in length, rivaling the size of its relative Carnotaurus.
Majungasaurus' skull, in contrast to most theropods, is extraordinarily well-documented. Its structure is generally in line with other abelisaurids, featuring a short length in proportion to its height. The premaxilla, found in the front upper jaw, lends the snout a blunt appearance, consistent with the family's characteristics. The external surface of the skull bones is textured, a trait shared by all abelisaurids. Majungasaurus, in particular, has extremely thick and fused nasal bones, bearing a prominent ridge along the part of the bone closest to the nostrils. Furthermore, a distinctive dome-like horn protrudes from the fused frontal bones on top of the skull. In life, these structures would likely have been covered with some type of integument, possibly keratin. CT scans of the skull reveal that both the nasal structure and frontal horn contained hollow sinus cavities, possibly to reduce weight.
Majungasaurus had a unique set of teeth, similar to other abelisaurids, featuring short crowns. It stood out with seventeen teeth in both the maxilla of the upper jaw and the dentary of the lower jaw, more than most abelisaurids, except Rugops. The hindlimbs were stout and short in relation to the body length, with the tibia (lower leg bone) of Majungasaurus being even stouter than that of its relative Carnotaurus. The tibia had a prominent crest on the knee. The ankle bones, the astragalus and calcaneum, were fused, and the feet bore three functional digits, with a smaller first digit that did not make contact with the ground.
The unique skull shape of Majungasaurus and other abelisaurids suggests different predatory behaviors compared to other theropods. Whereas most theropods had long, low, and narrow skulls, well-suited for vertical stress during a powerful bite, abelisaurid skulls were taller and wider, sometimes shorter in length as well. This contrast made abelisaurid skulls more capable of withstanding torsion, which is the twisting of the skull during a bite.
In comparison to modern mammalian predators, most theropods had feeding strategies resembling those of long-snouted canids. They delivered numerous bites to weaken their prey. Abelisaurids, particularly Majungasaurus, appear to have been adapted to a different strategy, akin to modern felids, with shorter, broader snouts that could deliver a single powerful bite and hold on until the prey was subdued. Several features of Majungasaurus, such as its reinforced neck, robust vertebrae, interlocking ribs, ossified tendons, and muscle attachment sites on the vertebrae and back of the skull, would have allowed it to maintain a steady grip on struggling prey. Additionally, the bones of abelisaurid skulls, including Majungasaurus, were fortified by skin-derived bone mineralization, giving them their characteristic rough texture.
Majungasaurus occupied the top of the food chain in its environment, preying on sauropods, which were enormously powerful creatures. Some evidence even points to Majungasaurus preying on other members of its own species, suggesting cannibalism.
