研究人员对活着的和已经灭绝的胎生哺乳动物的三维头骨数据集分析表明，演化率在早期达到顶峰并迅速减弱。在过去的6600万年中，这种长期的速度下降被创新的爆发所打断，而创新的幅度也在下降。社会性的、前社会性的、水生的和食草性的物种演化最快，特别是鲸鱼、大象、海牛类和已灭绝的有蹄类动物。啮齿类和蝙蝠的演化速度缓慢，表明分类学和形态学的多样化是不一致的。
令人沮丧的是，对胎生哺乳动物超群祖先形状的估计高度相似，表明它们最早的代表可能仍然无法得到明确的识别。
据介绍，新生代胎生哺乳动物的多样化是典型的适应性辐射。然而，分子分化估计和化石记录之间的差异助长了围绕这一辐射的时间、节奏和驱动因素的持续辩论。
附：英文原文
Title: Attenuated evolution of mammals through the Cenozoic
Author: Anjali Goswami, Eve Noirault, Ellen J. Coombs, Julien Clavel, Anne-Claire Fabre, Thomas J. D. Halliday, Morgan Churchill, Abigail Curtis, Akinobu Watanabe, Nancy B. Simmons, Brian L. Beatty, Jonathan H. Geisler, David L. Fox, Ryan N. Felice
Issue&Volume: 2022-10-28
Abstract: The Cenozoic diversification of placental mammals is the archetypal adaptive radiation. Yet, discrepancies between molecular divergence estimates and the fossil record fuel ongoing debate around the timing, tempo, and drivers of this radiation. Analysis of a three-dimensional skull dataset for living and extinct placental mammals demonstrates that evolutionary rates peak early and attenuate quickly. This long-term decline in tempo is punctuated by bursts of innovation that decreased in amplitude over the past 66 million years. Social, precocial, aquatic, and herbivorous species evolve fastest, especially whales, elephants, sirenians, and extinct ungulates. Slow rates in rodents and bats indicate dissociation of taxonomic and morphological diversification. Frustratingly, highly similar ancestral shape estimates for placental mammal superorders suggest that their earliest representatives may continue to elude unequivocal identification.
DOI: abm7525
Source: https://www.science.org/doi/10.1126/science.abm7525