The manatees and wallaby might need extra teeth to cope with their tough meals – meadow grass and ferns respectively, which both contain hard, abrasive silica crystals. But the silvery mole rat ...

That hideous looking thing at the top of the page is an African Mole-rat, Heliophobius argenteocinereus, and it uses a system best described as an escalator. The teeth start low and at the back of ...