Megalosaurus

MEANING: Great lizard

PERIOD: Middle Jurassic

CONTINENT: Europe

Megalosaurus was the first non-avian dinosaur to be validly named, and played a pivotal role in scientific understanding of prehistoric life. Among the largest of Middle Jurassic theropods, it is estimated between 6-9 m long, weighing about 1 t. Megalosaurus, along with Iguanodon and Hylaeosaurus defined what is considered a dinosaur to this day.

Megalosaurus is from the Middle Jurassic. The Middle Jurassic, spanning from approximately 174 to 163 million years ago, was a period of increasing tectonic activity and evolutionary innovation. By this time, the supercontinent Pangaea had begun to split more significantly, with Laurasia in the north and Gondwana in the south drifting apart. This movement created new coastlines, shallow seas, and rift valleys that fostered diverse ecosystems. The climate remained generally warm and humid, promoting the spread of lush vegetation, including ferns, cycads, and conifers, which blanketed much of the land and supported a wide variety of herbivorous dinosaurs.

Though less well known than the Late Jurassic, the Middle Jurassic was an important evolutionary chapter. Several major dinosaur groups began to diversify, including the stegosaurs and more derived long-necked sauropods that would later dominate the landscape. Theropods also continued to evolve, giving rise to new lineages like the megalosaurids and the early ancestors of more derived carnivores. Fossil evidence from this interval is relatively scarce compared to later stages, but what we do have paints a picture of an increasingly complex world, setting the stage for the iconic ecosystems of the Late Jurassic.

Megalosaurus is a megalosaurid. Megalosauridae was an early group of large theropod dinosaurs that thrived during the Middle to Late Jurassic. As some of the first truly giant carnivores, they played a key role as apex predators in many ecosystems of their time. Characterized by robust skulls, powerful jaws, and strong forelimbs with three-fingered hands, megalosaurids were built for strength and versatility. Though not as specialized as some of the theropods that would follow, they marked a significant evolutionary step beyond earlier, smaller predators.

Megalosaurids are mainly thought of as a European group, but fossils have also been found in North and South America, Africa, and possibly Asia, suggesting they were relatively widespread. This pattern of dispersal shows that megalosaurids were successful and adaptable carnivores, able to fill top predator roles across a variety of environments before the rise of more derived theropod groups later in the Jurassic.