Data from: Eutherians experienced elevated evolutionary rates in the immediate aftermath of the Cretaceous–Palaeogene mass extinction

The effect of the Cretaceous–Palaeogene (K–Pg) mass extinction on the evolution of many groups, including placental mammals, has been hotly debated. The fossil record suggests a sudden adaptive radiation of placentals immediately after the event, but several recent quantitative analyses have reconstructed no significant increase in either clade origination rates or rates of character evolution in the Palaeocene. Here we use stochastic methods to date a recent phylogenetic analysis of Cretaceous and Palaeocene mammals and show that Placentalia likely originated in the Late Cretaceous, but that most intraordinal diversification occurred during the earliest Palaeocene. This analysis reconstructs fewer than 10 placental mammal lineages crossing the K–Pg boundary. Moreover, we show that rates of morphological evolution in the 5 Myr interval immediately after the K–Pg mass extinction are three times higher than background rates during the Cretaceous. These results suggest that the K–Pg mass extinction had a marked impact on placental mammal diversification, supporting the view that an evolutionary radiation occurred as placental lineages invaded new ecological niches during the Early Palaeocene.

白垩纪-古近纪（Cretaceous–Palaeogene，简称K-Pg）集群灭绝事件对包括有胎盘哺乳动物在内的诸多类群演化的影响，长期以来广受学界争论。化石记录显示，有胎盘哺乳动物在该事件发生后随即出现了突发性的适应性辐射，但近期多项定量分析均未在古新世时期检测到支系起源速率或性状演化速率存在显著提升的结果。本研究运用随机方法对一项新近的白垩纪与古新世哺乳动物系统发育分析进行年代校准，结果表明：有胎盘类（Placentalia）大概率起源于白垩纪晚期，但绝大多数目内分化事件均发生在古新世早期。本次分析重建出跨越K-Pg界线的有胎盘哺乳动物支系不足10支。此外，本研究还发现，K-Pg集群灭绝后最初5百万年的形态演化速率是白垩纪背景演化速率的3倍。上述结果表明，K-Pg集群灭绝事件对有胎盘哺乳动物的多样化进程具有显著影响，支持了“古新世早期有胎盘类谱系入侵全新生态位并引发演化辐射”的学术观点。