Abstract: The incisor enamel microstructure of Mina hui Li et al., 2016 from the upper Wanghudun Formation, Middle Paleogene of Qianshan, Anhui is described following the hierarchical system ranging from crystallites to Schmelzmuster. The enamel sample was taken from the upper incisor of the holotype. The enamel consists of a very thin prismless external layer, a relatively thick outer layer (PE) with radial enamel and an inner layer (PI) with multilayered Hunter-Schreger bands (HSB). The thickness of HSB is irregular and the inclination has a small angle; no transition zones between the HSB; prism cross sections are irregularly round; interprismatic matrix is very thick with crystallites in the PE running parallel to the prism long axes. These characters resemble pauciserial HSB in rodents.Ribbon-like prism seams and convergent crystallite discontinuities areconsistent in different portions of the enamel, which are interpreted as a primitive feature for Glires, or even placental mammals. Compared with known enamel structure of basal Glires, the enamel of Minastands for the earliest known evidence of double-layered enamel of the group. It indicates that the early evolution of Glires and placental mammals is complex and adds more details to the enamel microstructure of the earliest Glires.  

摘要： 从晶体类型到釉质结构4个不同的微观结构等级详细描述了安徽潜山中古新世胡氏敏兽的门齿釉质微观结构。样品取自胡氏敏兽正型标本的上门齿后端。该门齿最外层为一极薄的无釉柱层，外层为放射状釉柱层，内层为具多层的施氏明暗带。施氏明暗带的单带厚度变化较大，倾斜度相对较小，带间无明显的过渡带，釉柱的横切面为不规则圆形，釉柱间质较厚，外层间质晶体平行于釉柱长轴。这些特征与啮齿类中的散系施氏明暗带极为相似。同时还发现有缎状的釉柱中缝和聚敛型的晶体间断分布在釉质的不同部位，而这些特征一般被认为是啮形类，甚至是哺乳动物的较为原始特征。与其他已报道的基干啮型类对比，胡氏敏兽的门齿釉质代表了啮形类中已知最早的双层似散系釉质类型，具有更多的较原始特征，为啮形类门齿釉质研究提供了更多的形态学信息，并显示啮形类的演化可能远比现在认知的复杂。