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  • Hunter-Schreger bands, commonly abbreviated as HSB, are features of the enamel of the teeth in mammals, mostly placentals. In HSB, enamel prisms are arranged in layers of varying thickness at about right angles to each other. HSB strengthen the enamel and prevent cracks from propagating through the tooth. HSB are first observed in early Paleocene mammals, but at this time the HSB occupy only a small portion of the incisor and the angle between the bands is low. By the late Paleocene, HSB is seen to extend throughout the enamel and the bands are located at nearly right angles to each other. Under oblique reflected light HSB can be seen as dark and light strips of variable width. Among Glires, the group containing rodents, lagomorphs, and their primitive relatives, the absence of HSB from the incisors has been considered primitive. Some early representatives, including Eurymylus, lack HSB, but others, including Matutinia and some mimotonids, have double-layered incisor enamel with HSB in the inner portion. Other mimotonids have single-layered enamel with HSB. All leporids studied also exhibit this pattern, except for an early Eocene, indeterminate leporid with HSB only in the PI.