In which era were dinosaurs the dominant vertebrates?

• A. Paleozoic
• B. Mesozoic
• C. Cenozoic
• D. Precambrian

Answer: (B)

Dinosaurs became the dominant vertebrates during the Mesozoic era, roughly 252 to 66 million years ago, often called the Age of Dinosaurs. In this era, they diversified into many lineages and filled most ecological roles on land, from colossal herbivores to formidable predators and even flying forms that gave rise to birds toward the end. While mammals existed, they were generally small and did not outcompete the dinosaurs for dominance for most of this time. The Mesozoic is divided into Triassic, Jurassic, and Cretaceous periods, during which different dinosaur groups rose and spread, maintaining their prominence until the end of the era. That boundary marks a mass extinction that wiped out most dinosaurs, paving the way for mammals to become the dominant vertebrates in the following era. The Paleozoic existed earlier, with different dominant life forms, and the Precambrian predates complex multicellular life, while the Cenozoic comes after the dinosaur extinction.