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".
The animal, which is written about in Royal Society journal Biology Letters , shares some characteristics with shrew rats from the Philippines, but has taken a further evolutionary step by completely losing its chewing molars.
"There are more than 2,200 rodent species in the world and until this discovery all had molars in the back of their mouth and incisors at the front," said Dr Kevin Rowe, from Museum Victoria in Australia, a member of the discovery team.
"This is an example of how species, when faced with a new ecological opportunity, in this case an abundance of earthworms, can evolve the loss of traits that were wildly successful in previous circumstances."
Co-author Anang Achmadi, from Museum Zoologicum Bogoriense in Indonesia, said: "The specialised incisors of rodents give them the distinct ability to gnaw - a defining characteristic of rodents worldwide.
"In having lost all teeth except a pair of unusually shaped incisors that are incapable of gnawing, this new rat is unique among rodents."
Dr Rowe said the find was a reminder that wild habitats can still harbour undiscovered species.
"In the mountains of Sulawesi, where we discovered paucidentomys, healthy forests still nurture rare and remarkable species, however, they are isolated patches imperilled by expanding logging, mining, plantations and other human activities."