全北区古近纪的鸟类动物群

PALEOGENE AVIFAUNA OF THE HOLARCTIC

中国的较高纬度地区有着丰富且交通无阻的含化石地层,故在全北区生物地理的研究中占有独特的位置。它提供了欧洲和北美新生代早期沉积之间的联系。这些动物群中所含丰富多样的鸟类动物群,直到目前才得到足够的关注。早始新世时,在全球范围内,甚至在高纬度地区,都遍布着热带森林;在怀俄明州的绿河湖区,还发现了棕榈叶的化石。因而,德国Messel的鸟类动物群表现出与非洲热带森林较近的亲缘关系,怀俄明州绿河的鸟类动物群与南美洲热带地区关系密切,也就不足为奇了。实际上,古近纪的标志性特征是温暖潮湿的生态系统在全球广泛分布,削弱了高纬度地区对生物分布所起的屏障作用。晚始新世-渐新世全球温度的下降,致使新近纪加剧了大陆隔离并促成了生态变化,进而导致了现代鸟类在分类上的多样性。

China occupies a unique position in studies of Holarctic biogeography by having rich and accessible fossil deposits at relatively high latitudes.It provides a connection between the early Cenozoic deposits of Europe and North America.These faunas contain a diverse avifauna that is only now receiving adequate attention.The Early Eocene was a time of world-wide tropical forests,even at high latitudes（Martin,1994）,and the Green River lakes in Wyoming preserve the fossil leaves of palm trees.It is no surprise that the avifauna of Messel,Germany shows affinity with the tropical forests of Africa and that of the Green River in Wyoming with Tropical South America.In fact,the signature feature of the Paleogene was a universal distribution of warm moist ecosystems resulting in a reduction of the effectiveness of high latitude barriers to distribution.The Late Eocene-Oligocene drop in global temperatures resulted in increased continental isolation and precipitated the ecological changes that characterize the Neogene and resulted in the modern taxonomic diversity of birds.