An unusual species of rat that cannot gnaw or chew has been discovered, which scientists say is a new step in rodent evolution.

The rodent, called paucidentomys vermidax, has fang-like upper incisors that are useless for gnawing and no back teeth.

The rat, which lives exclusively on earthworms, was found in remote rainforest on the Indonesian island of Sulawesi.

It has a rat's tail, a long, thin nose similar to a shrew's and its only teeth are incisors which are in the upper jaw and end in twin points.

The genus name paucidentomys means "few-toothed mouse" and the species name vermidax means "devourer of worms".