Four ‘routes’, Beringian, De Geer, Thulean and Turgai Strait, are currently considered to explain Cenozoic continental interchanges between Eurasia and North America. These ‘routes’ had a crucial importance for vertebrates and insects. While vertebrates are not infrequent in these zones, there is very little direct evidence of insects to date the migrations and justify particular ‘routes’. A ‘route’ is generally chosen on the basis of indirect evidence, such as molecular dating of clades. Alaska, on the Beringian ‘route’, is especially poor in fossil insects. Here we describe the first two Paleocene–Eocene insects from the Chickaloon Formation in Alaska, viz. Basiaeschna alaskaensis sp. nov., the first accurate fossil of this extant Nearctic aeshnid genus, and a representative of the extinct damselfly family Dysagrionidae, distributed in the Palaeogene of Eurasia and North America. These fossils provide direct evidence of the role of Beringia as a land bridge for insects during the Palaeogene. They are also evidence for a warm temperate climate in Alaska during this period of global warmth.

http://zoobank.org/urn:lsid:zoobank.org:pub:574EBAB4-EEDE-41B4-A520-FAC650084914

目前考虑使用四个“路线”，即白令山脉，德格尔，图林和图尔盖海峡，来解释欧亚大陆与北美之间的新生代大陆互换。这些“路线”对脊椎动物和昆虫至关重要。尽管这些地区的脊椎动物并不常见，但很少有直接证据表明昆虫能说明这些迁徙的年代并为特定的“路线”辩护。通常根据间接证据（例如进化枝的分子测年法）来选择“路线”。在白令山脉“路线”上的阿拉斯加特别缺乏化石昆虫。在这里，我们描述了从阿拉斯加，Chickaloon组的前两个古新世-始新世昆虫即。阿拉斯加Basiaeschnasp。十一月，这是现存的近北古猿属的第一个精确化石，也是灭绝的豆娘科Dysagrionidae的代表，分布于欧亚大陆和北美的古近纪。这些化石直接提供了白灵菌在古近代时期作为昆虫的陆桥的作用的证据。它们也是全球变暖时期阿拉斯加温暖带气候的证据。

http://zoobank.org/urn:lsid:zoobank.org:pub:574EBAB4-EEDE-41B4-A520-FAC650084914