Triassic period
Geological period spanning roughly 252–201 million years ago. Used in scientific and educational contexts.
The Triassic period is when dinosaurs first appeared.
Fossils were discovered in Triassic strata.
The term 三畳紀 is a Japanese calque of the English 'Triassic', using 三 (three) and 畳 (fold/layer) to represent the three distinct rock layers first identified in Germany, plus 紀 (period).