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(wàn)至2300萬(wàn)年前) the Paleogene period 古第三紀(jì) Paleogene flora and fauna 古第三紀(jì)動(dòng)植物 the Paleogene noun [ 單數(shù)名詞 ] the Paleogene period 古第三紀(jì) 返回 Paleogene