Rajasaurus

MEANING: King lizard

PERIOD: Late Cretaceous

CONTINENT: Asia

Typical to abelisaurids, Rajasaurus made up for its short four fingered arms with its heavily-constructed head as its primary tool for hunting. Rajasaurus measured about 7 m in length, and had a single horn on the forehead which was probably used for display and head-butting. Like other abelisaurids, Rajasaurus was probably an ambush predator.

Rajasaurus is from the Late Cretaceous. The Cretaceous is the third and final geological period of the Mesozoic Era, with the Late Cretaceous making up roughly the second half of it, lasting from about 100 to 66 million years ago. It was a time of significant evolutionary change, with dinosaurs reaching their greatest diversity before the mass extinction at the end of the Cretaceous.

The Cretaceous was a period with a relatively warm climate, though the Late Cretaceous experienced a global cooling trend, caused by falling levels of carbon dioxide in the atmosphere. The continents were nearing their present positions, but high sea levels flooded low-lying regions, turning Europe into an archipelago, and forming the Western Interior Seaway in North America. These seas were home to a variety of marine reptiles, including mosasaurs and plesiosaurs, while pterosaurs and birds shared the skies.

On land, dinosaurs continued to thrive and diversify during the Late Cretaceous, producing many of the most well-known goups, including tyrannosaurs, hadrosaurs, and pachycephalosaurs. Established Cretaceous dinosaur clades like the ceratopsians, ankylosaurs, and dromaeosaurs continued to flourish. Sauropod species consisted almost exclusively of titanosaurs, which seemed to be confined to the Southern Hemisphere for much of the Late Cretaceous. Flowering plants and grasses diversified and spread, becoming the dominant flora similar to what we see today.

The Cretaceous (along with the Mesozoic) ended with the Cretaceous-Paleogene (K-Pg) extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. This event, likely triggered by an asteroid impact, is marked by the abrupt K-Pg boundary, a distinct geologic layer separating the Mesozoic and Cenozoic Eras. In its aftermath, mammals and avian dinosaurs rapidly diversified, becoming the dominant land animals of the Cenozoic Era.

Rajasaurus is an abelisaur. Abelisauria was a distinctive group of theropod dinosaurs that flourished mainly in the southern continents during the Cretaceous Period. They are part of the larger clade Ceratosauria, which split from other theropods early in dinosaur evolution. Abelisaurs are best known for their unusual body proportions, including deep short skulls often ornamented with ridges, horns, or rough-textured bone, and their extremely small vestigial forearms. Their legs, however, were strong and built for active movement, suggesting they were effective predators.

Fossil evidence of abelisaurs has been found across South America, Africa, Madagascar, India, and parts of Europe, reflecting their dominance in Gondwana during the Late Cretaceous. As ecosystems in the Southern Hemisphere evolved separately from those in the north, abelisaurs took on the top predator roles that tyrannosaurs filled in North America and Asia. Their prevalence in isolated landmasses hints at how regional evolution shaped dinosaur diversity differently across the globe. Despite their strange appearance, abelisaurs were well-adapted hunters, and they remained successful up until the Cretaceous-Paleogene extinction event.