Triassic

adjective

designating or of the first geologic period of the Mesozoic Era, characterized by the breakup of Pangea, the development of tall forests of cycads and conifers, and the presence of the first dinosaurs, turtles, frogs, and small mammals

Etymology: < Ger triassisch (< LL Trias (see triad: because divisible into three groups) + -isch, -ic