Fossilized Mammoth Tooth
Woolly mammoths had four functional molar teeth at a time, two in the upper jaw and two in the lower. About 23 cm (9.1 in) of the crown was within the jaw, and 2.5 cm (1 in) was above. The crown was continually pushed forwards and up as it wore down, comparable to a conveyor belt. The teeth had up to 26 separated ridges of enamel, which were themselves covered in "prisms" that were directed towards the chewing surface. These were quite wear resistant and kept together by cementum and dentine. A mammoth had six sets of molars throughout a lifetime, which were replaced five times, though a few specimens with a seventh set are known.