The fossil birds of the early Cenozoic (Paleogene-Neogene) are clearly attributable to the modern birds, and the earliest well-estabished record of most traditional orders and families of modern birds occur then.

• 新生代早期（包括古近纪和新近纪）鸟类的分类已被清晰地归入到现生鸟类中，并且现生鸟类传统的“目”“科”类型在早期已经出现并确立。