Eutherian morphological disparity across the end-Cretaceous mass extinction

In the aftermaths of mass extinction events, during radiations of clades, and in several other evolutionary scenarios, there is often a decoupling of taxonomic diversity and morphological disparity. The placental mammal radiation after the end-Cretaceous mass extinction is one of the archetypal adaptive radiations, but the change in morphological disparity of the entire skeleton has never been quantified across this important boundary. We reconstruct ancestral morphologies of 680 discrete morphological characters onto dated phylogenies of 177 mostly Cretaceous and Palaeogene eutherians (placental mammals and their stem relatives). Using a new approach to incorporate morphologies representing ghost lineages, we assess three measures of morphological disparity (sum of ranges, sum of variances and mean pairwise dissimilarity) across stage-level time bins within the Cretaceous and Palaeogene. We find that the range-based metric suggests that eutherian disparity increased immediately after t...在大灭绝事件之后、支系（clade）辐射演化期间，以及其他多种演化场景中，分类多样性与形态差异度（morphological disparity）时常发生解耦现象。白垩纪末期大灭绝事件后的胎盘类哺乳动物辐射演化，是典型的适应辐射案例之一，但学界尚未针对这一重要演化界线，量化过整个骨骼系统的形态差异度变化。我们针对177种（绝大多数为白垩纪与古近纪真兽类（eutherian）——即胎盘类哺乳动物及其干群类群），基于定年系统发育树，重建了680个离散形态特征的祖先形态。我们采用一种纳入幽灵支系（ghost lineage）代表形态的新方法，对白垩纪与古近纪内各阶级时间间隔下的形态差异度开展了三项指标评估：范围总和、方差总和与平均成对相异度。我们发现，基于范围的指标表明，真兽类的形态差异度在……之后即刻出现了上升。