Data from: Therian mammals experience an ecomorphological radiation during the Late Cretaceous and selective extinction at the K-Pg boundary

It is often postulated that mammalian diversity was suppressed during the Mesozoic Era and increased rapidly after the Cretaceous–Palaeogene (K–Pg) extinction event. We test this hypothesis by examining macroevolutionary patterns in early therian mammals, the group that gave rise to modern placentals and marsupials. We assess morphological disparity and dietary trends using morphometric analyses of lower molars, and we evaluate generic level taxonomic diversity patterns using techniques that account for sampling biases. In contrast with the suppression hypothesis, our results suggest that an ecomorphological diversification of therians began 10–20 Myr prior to the K–Pg extinction event, led by disparate metatherians and Eurasian faunas. This diversification is concurrent with ecomorphological radiations of multituberculate mammals and flowering plants, suggesting that mammals as a whole benefitted from the ecological rise of angiosperms. In further contrast with the suppression hypothesis, therian disparity decreased immediately after the K–Pg boundary, probably due to selective extinction against ecological specialists and metatherians. However, taxonomic diversity trends appear to have been decoupled from disparity patterns, remaining low in the Cretaceous and substantially increasing immediately after the K–Pg extinction event. The conflicting diversity and disparity patterns suggest that earliest Palaeocene extinction survivors, especially eutherian dietary generalists, underwent rapid taxonomic diversification without considerable morphological diversification.

学界普遍认为，中生代时期哺乳动物的多样性受到抑制，并在白垩纪-古近纪（K-Pg）灭绝事件后迅速提升。我们通过研究早期兽类哺乳动物（therian mammals）——即现代胎盘类与有袋类的祖先类群——的宏观演化格局，对这一假说进行验证。我们借助下臼齿的形态测量分析评估形态差异度与食性演化趋势，并采用考虑采样偏差的方法分析属级分类多样性格局。与“多样性受抑制”假说相悖的是，我们的研究结果显示，兽类的生态形态多样化始于K-Pg灭绝事件前1000万至2000万年，这一过程以多样的后兽类与欧亚动物区系为先导。该多样化事件与多瘤齿兽类哺乳动物和被子植物的生态形态辐射同步发生，表明整体而言哺乳动物类群受益于被子植物的生态崛起。进一步与该假说相悖的是，兽类的形态差异度在K-Pg界线后即刻下降，这一现象可能缘于针对生态特化类群与后兽类的选择性灭绝。不过，分类多样性的演化趋势似乎与形态差异度格局脱钩：白垩纪时期多样性始终处于低位，而在K-Pg灭绝事件后即刻大幅提升。多样性与差异度的矛盾格局表明，古新世最早的灭绝幸存者——尤其是真兽类食性泛化者——在未发生显著形态多样化的情况下，实现了快速的分类多样性扩张。