Data from: Mammals across the K/Pg boundary in northeastern Montana, U.S.A.: dental morphology and body-size patterns reveal extinction selectivity and immigrant-fueled ecospace filling

The Cretaceous/Tertiary (K/Pg) mass extinction has long been viewed as a pivotal event in mammalian evolutionary history, in which the extinction of non-avian dinosaurs allowed mammals to rapidly expand from small-bodied, generalized insectivores to a wide array of body sizes and ecological specializations. Many studies have used global- or continental-scale taxonomic databases to analyze this event on coarse temporal scales, but few studies have documented morphological diversity of mammalian paleocommunities on fine spatiotemporal scales in order to examine ecomorphological selectivity and ecospace filling across this critical transition. Focusing on well-sampled and temporally well-constrained mammalian faunas across the K/Pg boundary in northeastern Montana, I quantified dental-shape disparity and morphospace occupancy via landmark- and semilandmark-based geometric morphometrics and mean body size, body-size disparity, and body-size structure via body-mass estimates. My results reveal several key findings: (1) latest Cretaceous mammals, particularly metatherians and multituberculates, had a greater ecomorphological diversity than is generally appreciated, occupying regions of the morphospace that are interpreted as strict carnivory, plant-dominated omnivory, and herbivory; (2) the decline in dental-shape disparity and body-size disparity across the K/Pg boundary shows a pattern of constructive extinction selectivity against larger-bodied dietary specialists, particularly strict carnivores and taxa with plant-based diets, that suggests the kill mechanism was related to depressed primary productivity rather than a globally instantaneous event; (3) the ecomorphological recovery in the earliest Paleocene was fueled by immigrants, namely three multituberculate families (taeniolabidids, microcosmodontids, eucosmodontids) and to a lesser extent archaic ungulates; and (4) despite immediate increases in the taxonomic richness of eutherians, their much-celebrated post-K/Pg ecomorphological expansion had a slower start than is generally perceived and most likely only began 400,000 to 1 million years after the extinction event.白垩纪/古近纪（K/Pg）生物大灭绝长期以来被视为哺乳动物演化史上的关键事件：非鸟类恐龙（non-avian dinosaurs）的灭绝使得哺乳动物得以从小型泛化食虫类快速辐射，演化出多样的体型与生态特化类型。此前诸多研究依托全球或大陆尺度的分类学数据库，在较粗的时间尺度上分析该事件，但鲜有研究通过精细时空尺度下的哺乳动物古群落形态多样性，来探究该关键过渡阶段的生态形态选择性与生态位填充过程。 本研究聚焦蒙大拿州东北部K/Pg界线附近采样充分、时间约束明确的哺乳动物群，通过基于标志点与半标志点的几何形态测量学量化牙齿形状差异度与形态空间占据度，并依托体重估算值计算平均体重、体型差异度与体型结构。 本研究得到四项核心发现：（1）最晚白垩世哺乳动物（尤其是后兽类（metatherians）与多瘤齿兽类（multituberculates））的生态形态多样性远超此前认知，它们占据了被判定为严格食肉、以植物为主的杂食以及植食的形态空间区域；（2）K/Pg界线两侧牙齿形状差异度与体型差异度的下降呈现出针对体型较大的特化食性类群（尤其是严格食肉类与植食性类群）的选择性灭绝模式，这表明灭绝机制与初级生产力下降相关，而非全球性瞬时事件；（3）最早古新世的生态形态恢复由迁入类群驱动，主要包括三科多瘤齿兽类：塔尼欧兽科（taeniolabidids）、小颅兽科（microcosmodontids）与真多瘤齿兽科（eucosmodontids），另有少量原始有蹄类（archaic ungulates）；（4）尽管真兽类（eutherians）的分类丰富度在灭绝事件后快速提升，但其广为人知的K/Pg后生态形态扩张的启动时间远慢于此前认知，大概率仅在灭绝事件发生后的40万至100万年才真正开启。