The silvery mole rat of Kenya and Tanzania continually replaces its molars in an unsettlingly shark-like way. New ones sprout from the back of its jaw and slowly make their way forwards. The front ones, having been ground away, are absorbed.

Back in 1957, Stuart Landry first noted that the mole rat has more molars than other rodents – up to seven, compared to the usual four or five. No one picked up on that piece of information for decades, until Helder Gomes Rodrigues from the University of Lyon decided to give the teeth another look.

He studied 55 different skulls and saw that most have molars at the back of their jaws that are about to erupt. As they