劍橋詞典from or referring to the period of time between about 66 and 23 million years ago, in which many insects , mammals , and birds appeared 古第三紀(jì)的（迄今6600萬至2300萬年前） the Paleogene period 古第三紀(jì) Paleogene flora and fauna 古第三紀(jì)動植物 the Paleogene noun [ 單數(shù)名詞 ] the Paleogene period 古第三紀(jì) 返回 Paleogene