Three new Jurassic euharamiyidan species reinforce early divergence of mammals

摘要

Haramiyids是极为古老的化石哺乳动物，直到最近人们也只是从牙齿知道它们，被认为与已经灭绝、但却极为成功的、类似啮齿类的多尖齿兽相关。头骨和骨架的发现只是让人们更加糊涂——一篇论文证实了它们与多尖齿兽之间的联系，而另一篇论文则质疑这种联系。现在，Jin Meng及同事介绍了来自中国侏罗纪时期的三个新种haramiyid，从而确认了它们与尖齿兽之间的联系，同时也显示：今天仍存在的哺乳动物类群之间(一边是单孔目，另一边是有袋类和有胎盘类)的最初分化是非常久远的，可以追溯到三叠纪时期。%The phylogeny of Allotheria, including Multituberculata and Haramiyida, remains unsolved and has generated contentious views on the origin and earliest evolution of mammals. Here we report three new species of a new clade, Euharamiyida, based on six well-preserved fossils from the Jurassic period of China. These fossils reveal many craniodental and post-cranial features of euharamiyidans and clarify several ambiguous structures that are currently the topic of debate. Our phylogenetic analyses recognize Euharamiyida as the sister group of Multituberculata, and place Allotheria within the Mammalia. The phylogeny suggests that allotherian mammals evolved from a Late Triassic (approximately 208 million years ago) Haramiyavia-like ancestor and diversified into euharamiyidans and multituberculates with a cosmopolitan distribution, implying homologous acquisition of many craniodental and postcranial features in the two groups. Our ear bones during mammalian evolution.