During which period did the first large herbivores and carnivores appear?

The first large herbivores and carnivores appeared during the Mesozoic Era, which is divided into three periods-- Triassic, Jurassic and Cretaceous. The herbivores and and carnivores increased in size during the Jurassic Period. And some of the largest dinosaurs emerged during this period as well.

50 meters per 5 seconds