noun
Triassic period
Geological period spanning roughly 252–201 million years ago. Used in scientific and educational contexts.
三畳紀は恐竜が出現した時代です。
The Triassic period is when dinosaurs first appeared.
三畳紀の地層から化石が発見された。
Fossils were discovered in Triassic strata.
The Cretaceous period, which follows the Jurassic.
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).