During the Mesozoic Era, the earliest dinosaurs appeared.
14- A) Dinosaurs. Dinosaurs were a type of reptile that lived during the Mesozoic Era. They were the dominant terrestrial vertebrates during this era and exhibited great diversity in size, shape, and behaviour. Reptiles (option B) in general were present during the Mesozoic Era, but dinosaurs specifically were unique to that time period. Mammals (option C) and birds (option D) also existed during the Mesozoic Era, but they were not as dominant as dinosaurs.