Abstract: The roles of immigration and endemic radiation of survivors of the extinctions marking the Cretaceous/Tertiary (K/T) boundary in evolution of the earliest Paleocene (Puercan) mammalian fauna of the North American Western Interior have been debated. Continued field and laboratory research has significantly expanded and refined knowledge of the compositions of North American latest Cretaceous (Lancian North American Land Mammal Age) and Puercan 1 (Pu1) local faunas. It has also revealed limitations in biochronological correlations of these local faunas. In general, Pu1 local faunas of the northern Western Interior reflect the extinction or extirpation of lineages of Lancian marsupials and consist primarily of multituberculate and eutherian mammals. The majority of Pu1 mammals were immigrants, many dispersing into the area soon after the K/T boundary. Testing the hypothesis of Asian origins of the immigrants is hampered by lack of latest Cretaceous or earliest Paleocene mammalian local faunas particularly from high North American paleolatitudes and Pacific coastal areas of Asia. Another working hypothesis, that most, if not all, of the Pu1 immigrant mammals entering the northern Western Interior could have dispersed from other areas of the North American continent has increasing support and has yet to be falsified.

摘要： K/T界线绝灭事件后残存类群的迁入和地方性辐射在北美西部内陆地区的古新世最早期(Puercan期)哺乳动物群的进化中所起的作用存在争议。持续的野外工作和室内研究极大地扩展和提升了我们对北美地区的白垩纪最晚期(北美陆相哺乳动物分期的Lancian期)和Puercan 1期(Pu1)的地方动物群组成的认识，也揭示了这些地方动物群的生物年代学对比的局限。总的来说，北美西部内陆地区北部的Pu1地方动物群主要由多瘤齿兽类和真兽类组成，而Lancian期存在的有袋类各类群绝灭。大多数的Pu1哺乳动物是由其他地区迁移而来的，其中许多类群在K/T界线后不久就迁徙到这个地区。北美洲古纬度高的地区和亚洲太平洋沿岸地区的白垩纪最晚期或者古新世最早期哺乳动物群的缺乏，妨碍了对异地迁移到北美的哺乳动物起源于亚洲这一假说的验证。另一个假说认为，大多数迁入北美西部内陆地区北部的Pu1哺乳动物可能来自北美大陆的其他地区。这一假说得到了越来越多的支持，并且没有证据表明是错误的。